Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.
The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).
An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.
An aminoperhydroquinazoline poison found mainly in the liver and ovaries of fishes in the order TETRAODONTIFORMES, which are eaten. The toxin causes paresthesia and paralysis through interference with neuromuscular conduction.
Use of electric potential or currents to elicit biological responses.
Ion channels that specifically allow the passage of SODIUM ions. A variety of specific sodium channel subtypes are involved in serving specialized functions such as neuronal signaling, CARDIAC MUSCLE contraction, and KIDNEY function.
A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.
A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.
The hemodynamic and electrophysiological action of the HEART VENTRICLES.
The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.
Cell membrane glycoproteins that are selectively permeable to potassium ions. At least eight major groups of K channels exist and they are made up of dozens of different subunits.
The propagation of the NERVE IMPULSE along the nerve away from the site of an excitation stimulus.
The hollow, muscular organ that maintains the circulation of the blood.
An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
An impulse-conducting system composed of modified cardiac muscle, having the power of spontaneous rhythmicity and conduction more highly developed than the rest of the heart.
Conical muscular projections from the walls of the cardiac ventricles, attached to the cusps of the atrioventricular valves by the chordae tendineae.
Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.
The ability of a substrate to allow the passage of ELECTRONS.
One of the POTASSIUM CHANNEL BLOCKERS, with secondary effect on calcium currents, which is used mainly as a research tool and to characterize channel subtypes.
The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.
Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed)
Projection neurons in the CEREBRAL CORTEX and the HIPPOCAMPUS. Pyramidal cells have a pyramid-shaped soma with the apex and an apical dendrite pointed toward the pial surface and other dendrites and an axon emerging from the base. The axons may have local collaterals but also project outside their cortical region.
The lower right and left chambers of the heart. The right ventricle pumps venous BLOOD into the LUNGS and the left ventricle pumps oxygenated blood into the systemic arterial circulation.
Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.
A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.
Modified cardiac muscle fibers composing the terminal portion of the heart conduction system.
Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.
A class of drugs that act by inhibition of potassium efflux through cell membranes. Blockade of potassium channels prolongs the duration of ACTION POTENTIALS. They are used as ANTI-ARRHYTHMIA AGENTS and VASODILATOR AGENTS.
The period of time following the triggering of an ACTION POTENTIAL when the CELL MEMBRANE has changed to an unexcitable state and is gradually restored to the resting (excitable) state. During the absolute refractory period no other stimulus can trigger a response. This is followed by the relative refractory period during which the cell gradually becomes more excitable and the stronger impulse that is required to illicit a response gradually lessens to that required during the resting state.
Potassium channel whose permeability to ions is extremely sensitive to the transmembrane potential difference. The opening of these channels is induced by the membrane depolarization of the ACTION POTENTIAL.
Agents used for the treatment or prevention of cardiac arrhythmias. They may affect the polarization-repolarization phase of the action potential, its excitability or refractoriness, or impulse conduction or membrane responsiveness within cardiac fibers. Anti-arrhythmia agents are often classed into four main groups according to their mechanism of action: sodium channel blockade, beta-adrenergic blockade, repolarization prolongation, or calcium channel blockade.
Striated muscle cells found in the heart. They are derived from cardiac myoblasts (MYOBLASTS, CARDIAC).
Theoretical representations that simulate the behavior or activity of the cardiovascular system, processes, or phenomena; includes the use of mathematical equations, computers and other electronic equipment.
Any disturbances of the normal rhythmic beating of the heart or MYOCARDIAL CONTRACTION. Cardiac arrhythmias can be classified by the abnormalities in HEART RATE, disorders of electrical impulse generation, or impulse conduction.
A class of drugs that act by inhibition of sodium influx through cell membranes. Blockade of sodium channels slows the rate and amplitude of initial rapid depolarization, reduces cell excitability, and reduces conduction velocity.
Depolarization of membrane potentials at the SYNAPTIC MEMBRANES of target neurons during neurotransmission. Excitatory postsynaptic potentials can singly or in summation reach the trigger threshold for ACTION POTENTIALS.
Elements of limited time intervals, contributing to particular results or situations.
Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.
A group of slow opening and closing voltage-gated potassium channels. Because of their delayed activation kinetics they play an important role in controlling ACTION POTENTIAL duration.
A potassium-selective ion channel blocker. (From J Gen Phys 1994;104(1):173-90)
The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)
Electrical responses recorded from nerve, muscle, SENSORY RECEPTOR, or area of the CENTRAL NERVOUS SYSTEM following stimulation. They range from less than a microvolt to several microvolts. The evoked potential can be auditory (EVOKED POTENTIALS, AUDITORY), somatosensory (EVOKED POTENTIALS, SOMATOSENSORY), visual (EVOKED POTENTIALS, VISUAL), or motor (EVOKED POTENTIALS, MOTOR), or other modalities that have been reported.
Voltage-dependent cell membrane glycoproteins selectively permeable to calcium ions. They are categorized as L-, T-, N-, P-, Q-, and R-types based on the activation and inactivation kinetics, ion specificity, and sensitivity to drugs and toxins. The L- and T-types are present throughout the cardiovascular and central nervous systems and the N-, P-, Q-, & R-types are located in neuronal tissue.
Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.
Long-lasting voltage-gated CALCIUM CHANNELS found in both excitable and nonexcitable tissue. They are responsible for normal myocardial and vascular smooth muscle contractility. Five subunits (alpha-1, alpha-2, beta, gamma, and delta) make up the L-type channel. The alpha-1 subunit is the binding site for calcium-based antagonists. Dihydropyridine-based calcium antagonists are used as markers for these binding sites.
The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.
Contractile activity of the MYOCARDIUM.
The chambers of the heart, to which the BLOOD returns from the circulation.
A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.
The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability.
Neurons which activate MUSCLE CELLS.
The small mass of modified cardiac muscle fibers located at the junction of the superior vena cava (VENA CAVA, SUPERIOR) and right atrium. Contraction impulses probably start in this node, spread over the atrium (HEART ATRIUM) and are then transmitted by the atrioventricular bundle (BUNDLE OF HIS) to the ventricle (HEART VENTRICLE).
The hemodynamic and electrophysiological action of the HEART ATRIA.
Optical imaging techniques used for recording patterns of electrical activity in tissues by monitoring transmembrane potentials via FLUORESCENCE imaging with voltage-sensitive fluorescent dyes.
The innermost layer of the heart, comprised of endothelial cells.
Signal transduction mechanisms whereby calcium mobilization (from outside the cell or from intracellular storage pools) to the cytoplasm is triggered by external stimuli. Calcium signals are often seen to propagate as waves, oscillations, spikes, sparks, or puffs. The calcium acts as an intracellular messenger by activating calcium-responsive proteins.
A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.
The electrical properties, characteristics of living organisms, and the processes of organisms or their parts that are involved in generating and responding to electrical charges.
A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.
A class of drugs that act by selective inhibition of calcium influx through cellular membranes.
The function of opposing or restraining the excitation of neurons or their target excitable cells.
Most generally any NEURONS which are not motor or sensory. Interneurons may also refer to neurons whose AXONS remain within a particular brain region in contrast to projection neurons, which have axons projecting to other brain regions.
A conical fibro-serous sac surrounding the HEART and the roots of the great vessels (AORTA; VENAE CAVAE; PULMONARY ARTERY). Pericardium consists of two sacs: the outer fibrous pericardium and the inner serous pericardium. The latter consists of an outer parietal layer facing the fibrous pericardium, and an inner visceral layer (epicardium) resting next to the heart, and a pericardial cavity between these two layers.
An order of the class Amphibia, which includes several families of frogs and toads. They are characterized by well developed hind limbs adapted for jumping, fused head and trunk and webbed toes. The term "toad" is ambiguous and is properly applied only to the family Bufonidae.
The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.
An optical isomer of quinine, extracted from the bark of the CHINCHONA tree and similar plant species. This alkaloid dampens the excitability of cardiac and skeletal muscles by blocking sodium and potassium currents across cellular membranes. It prolongs cellular ACTION POTENTIALS, and decreases automaticity. Quinidine also blocks muscarinic and alpha-adrenergic neurotransmission.
Computer-based representation of physical systems and phenomena such as chemical processes.
A condition that is characterized by episodes of fainting (SYNCOPE) and varying degree of ventricular arrhythmia as indicated by the prolonged QT interval. The inherited forms are caused by mutation of genes encoding cardiac ion channel proteins. The two major forms are ROMANO-WARD SYNDROME and JERVELL-LANGE NIELSEN SYNDROME.
Refers to animals in the period of time just after birth.
The distal terminations of axons which are specialized for the release of neurotransmitters. Also included are varicosities along the course of axons which have similar specializations and also release transmitters. Presynaptic terminals in both the central and peripheral nervous systems are included.
A family of voltage-gated potassium channels that are characterized by long N-terminal and C-terminal intracellular tails. They are named from the Drosophila protein whose mutation causes abnormal leg shaking under ether anesthesia. Their activation kinetics are dependent on extracellular MAGNESIUM and PROTON concentration.
The time from the onset of a stimulus until a response is observed.
Substances used for their pharmacological actions on any aspect of neurotransmitter systems. Neurotransmitter agents include agonists, antagonists, degradation inhibitors, uptake inhibitors, depleters, precursors, and modulators of receptor function.
An element of the alkaline earth group of metals. It has an atomic symbol Ba, atomic number 56, and atomic weight 138. All of its acid-soluble salts are poisonous.
The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)
The largest portion of the CEREBRAL CORTEX in which the NEURONS are arranged in six layers in the mammalian brain: molecular, external granular, external pyramidal, internal granular, internal pyramidal and multiform layers.
Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.
A local anesthetic and cardiac depressant used as an antiarrhythmia agent. Its actions are more intense and its effects more prolonged than those of PROCAINE but its duration of action is shorter than that of BUPIVACAINE or PRILOCAINE.
A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.
A member of the alkali metals. It has an atomic symbol Cs, atomic number 50, and atomic weight 132.91. Cesium has many industrial applications, including the construction of atomic clocks based on its atomic vibrational frequency.
Sensory ganglia located on the dorsal spinal roots within the vertebral column. The spinal ganglion cells are pseudounipolar. The single primary branch bifurcates sending a peripheral process to carry sensory information from the periphery and a central branch which relays that information to the spinal cord or brain.
The synapse between a neuron and a muscle.
The most common inhibitory neurotransmitter in the central nervous system.
Recording of the moment-to-moment electromotive forces of the HEART as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a CATHODE RAY TUBE DISPLAY.
A potentially lethal cardiac arrhythmia that is characterized by uncoordinated extremely rapid firing of electrical impulses (400-600/min) in HEART VENTRICLES. Such asynchronous ventricular quivering or fibrillation prevents any effective cardiac output and results in unconsciousness (SYNCOPE). It is one of the major electrocardiographic patterns seen with CARDIAC ARREST.
The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold.
A shaker subfamily of potassium channels that participate in transient outward potassium currents by activating at subthreshold MEMBRANE POTENTIALS, inactivating rapidly, and recovering from inactivation quickly.
An adrenergic beta-antagonist that is used in the treatment of life-threatening arrhythmias.
Regulation of the rate of contraction of the heart muscles by an artificial pacemaker.
Contractile tissue that produces movement in animals.
Pyridines substituted in any position with an amino group. May be hydrogenated, but must retain at least one double bond.
The voltages across pre- or post-SYNAPTIC MEMBRANES.
An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.
Venoms from jellyfish; CORALS; SEA ANEMONES; etc. They contain hemo-, cardio-, dermo- , and neuro-toxic substances and probably ENZYMES. They include palytoxin, sarcophine, and anthopleurine.
An electrogenic ion exchange protein that maintains a steady level of calcium by removing an amount of calcium equal to that which enters the cells. It is widely distributed in most excitable membranes, including the brain and heart.
Specialized afferent neurons capable of transducing sensory stimuli into NERVE IMPULSES to be transmitted to the CENTRAL NERVOUS SYSTEM. Sometimes sensory receptors for external stimuli are called exteroceptors; for internal stimuli are called interoceptors and proprioceptors.
A superorder of CEPHALOPODS comprised of squid, cuttlefish, and their relatives. Their distinguishing feature is the modification of their fourth pair of arms into tentacles, resulting in 10 limbs.
The physiological mechanisms that govern the rhythmic occurrence of certain biochemical, physiological, and behavioral phenomena.
A class of nerve fibers as defined by their nerve sheath arrangement. The AXONS of the unmyelinated nerve fibers are small in diameter and usually several are surrounded by a single MYELIN SHEATH. They conduct low-velocity impulses, and represent the majority of peripheral sensory and autonomic fibers, but are also found in the BRAIN and SPINAL CORD.
The relationship between the dose of an administered drug and the response of the organism to the drug.
A trace element that is a component of vitamin B12. It has the atomic symbol Co, atomic number 27, and atomic weight 58.93. It is used in nuclear weapons, alloys, and pigments. Deficiency in animals leads to anemia; its excess in humans can lead to erythrocytosis.
Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM.
Clusters of multipolar neurons surrounded by a capsule of loosely organized CONNECTIVE TISSUE located outside the CENTRAL NERVOUS SYSTEM.
A highly neurotoxic polypeptide from the venom of the honey bee (Apis mellifera). It consists of 18 amino acids with two disulfide bridges and causes hyperexcitability resulting in convulsions and respiratory paralysis.
A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.
A superfamily of various freshwater CRUSTACEA, in the infraorder Astacidea, comprising the crayfish. Common genera include Astacus and Procambarus. Crayfish resemble lobsters, but are usually much smaller.
The rate dynamics in chemical or physical systems.
The cochlear part of the 8th cranial nerve (VESTIBULOCOCHLEAR NERVE). The cochlear nerve fibers originate from neurons of the SPIRAL GANGLION and project peripherally to cochlear hair cells and centrally to the cochlear nuclei (COCHLEAR NUCLEUS) of the BRAIN STEM. They mediate the sense of hearing.
Regularly spaced gaps in the myelin sheaths of peripheral axons. Ranvier's nodes allow saltatory conduction, that is, jumping of impulses from node to node, which is faster and more energetically favorable than continuous conduction.
Isopropyl analog of EPINEPHRINE; beta-sympathomimetic that acts on the heart, bronchi, skeletal muscle, alimentary tract, etc. It is used mainly as bronchodilator and heart stimulant.
A local anesthetic of the ester type that has a slow onset and a short duration of action. It is mainly used for infiltration anesthesia, peripheral nerve block, and spinal block. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1016).
A nerve which originates in the lumbar and sacral spinal cord (L4 to S3) and supplies motor and sensory innervation to the lower extremity. The sciatic nerve, which is the main continuation of the sacral plexus, is the largest nerve in the body. It has two major branches, the TIBIAL NERVE and the PERONEAL NERVE.
A chelating agent relatively more specific for calcium and less toxic than EDETIC ACID.
An isoquinoline alkaloid obtained from Dicentra cucullaria and other plants. It is a competitive antagonist for GABA-A receptors.
A shaker subfamily that is prominently expressed in NEURONS and are necessary for high-frequency, repetitive firing of ACTION POTENTIALS.
Drugs that bind to but do not activate excitatory amino acid receptors, thereby blocking the actions of agonists.
The tendency of a phenomenon to recur at regular intervals; in biological systems, the recurrence of certain activities (including hormonal, cellular, neural) may be annual, seasonal, monthly, daily, or more frequently (ultradian).
The nerves outside of the brain and spinal cord, including the autonomic, cranial, and spinal nerves. Peripheral nerves contain non-neuronal cells and connective tissue as well as axons. The connective tissue layers include, from the outside to the inside, the epineurium, the perineurium, and the endoneurium.
The movement of ions across energy-transducing cell membranes. Transport can be active, passive or facilitated. Ions may travel by themselves (uniport), or as a group of two or more ions in the same (symport) or opposite (antiport) directions.
The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.
The inferior (caudal) ganglion of the vagus (10th cranial) nerve. The unipolar nodose ganglion cells are sensory cells with central projections to the medulla and peripheral processes traveling in various branches of the vagus nerve.
Cells specialized to transduce mechanical stimuli and relay that information centrally in the nervous system. Mechanoreceptor cells include the INNER EAR hair cells, which mediate hearing and balance, and the various somatosensory receptors, often with non-neural accessory structures.
A voltage-gated sodium channel subtype that mediates the sodium ion PERMEABILITY of CARDIOMYOCYTES. Defects in the SCN5A gene, which codes for the alpha subunit of this sodium channel, are associated with a variety of CARDIAC DISEASES that result from loss of sodium channel function.
A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm.
Inorganic compounds that contain barium as an integral part of the molecule.
A network of tubules and sacs in the cytoplasm of SKELETAL MUSCLE FIBERS that assist with muscle contraction and relaxation by releasing and storing calcium ions.
The study of PHYSICAL PHENOMENA and PHYSICAL PROCESSES as applied to living things.
A technique for maintenance or growth of animal organs in vitro. It refers to three-dimensional cultures of undisaggregated tissue retaining some or all of the histological features of the tissue in vivo. (Freshney, Culture of Animal Cells, 3d ed, p1)
Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.
Interstitial space between cells, occupied by INTERSTITIAL FLUID as well as amorphous and fibrous substances. For organisms with a CELL WALL, the extracellular space includes everything outside of the CELL MEMBRANE including the PERIPLASM and the cell wall.
Drugs that bind to but do not activate GABA RECEPTORS, thereby blocking the actions of endogenous GAMMA-AMINOBUTYRIC ACID and GABA RECEPTOR AGONISTS.
A heterogenous group of transient or low voltage activated type CALCIUM CHANNELS. They are found in cardiac myocyte membranes, the sinoatrial node, Purkinje cells of the heart and the central nervous system.
A major nerve of the upper extremity. In humans, the fibers of the median nerve originate in the lower cervical and upper thoracic spinal cord (usually C6 to T1), travel via the brachial plexus, and supply sensory and motor innervation to parts of the forearm and hand.
Recording of the changes in electric potential of muscle by means of surface or needle electrodes.
An element with atomic symbol Cd, atomic number 48, and atomic weight 114. It is a metal and ingestion will lead to CADMIUM POISONING.
Annelids of the class Hirudinea. Some species, the bloodsuckers, may become temporarily parasitic upon animals, including man. Medicinal leeches (HIRUDO MEDICINALIS) have been used therapeutically for drawing blood since ancient times.
Characteristic properties and processes of the NERVOUS SYSTEM as a whole or with reference to the peripheral or the CENTRAL NERVOUS SYSTEM.
A potent excitatory amino acid antagonist with a preference for non-NMDA iontropic receptors. It is used primarily as a research tool.
An opisthobranch mollusk of the order Anaspidea. It is used frequently in studies of nervous system development because of its large identifiable neurons. Aplysiatoxin and its derivatives are not biosynthesized by Aplysia, but acquired by ingestion of Lyngbya (seaweed) species.
A malignant form of polymorphic ventricular tachycardia that is characterized by HEART RATE between 200 and 250 beats per minute, and QRS complexes with changing amplitude and twisting of the points. The term also describes the syndrome of tachycardia with prolonged ventricular repolarization, long QT intervals exceeding 500 milliseconds or BRADYCARDIA. Torsades de pointes may be self-limited or may progress to VENTRICULAR FIBRILLATION.
The D-enantiomer is a potent and specific antagonist of NMDA glutamate receptors (RECEPTORS, N-METHYL-D-ASPARTATE). The L form is inactive at NMDA receptors but may affect the AP4 (2-amino-4-phosphonobutyrate; APB) excitatory amino acid receptors.
Nerve structures through which impulses are conducted from a peripheral part toward a nerve center.
A methylpyrrole-carboxylate from RYANIA that disrupts the RYANODINE RECEPTOR CALCIUM RELEASE CHANNEL to modify CALCIUM release from SARCOPLASMIC RETICULUM resulting in alteration of MUSCLE CONTRACTION. It was previously used in INSECTICIDES. It is used experimentally in conjunction with THAPSIGARGIN and other inhibitors of CALCIUM ATPASE uptake of calcium into SARCOPLASMIC RETICULUM.
Branch-like terminations of NERVE FIBERS, sensory or motor NEURONS. Endings of sensory neurons are the beginnings of afferent pathway to the CENTRAL NERVOUS SYSTEM. Endings of motor neurons are the terminals of axons at the muscle cells. Nerve endings which release neurotransmitters are called PRESYNAPTIC TERMINALS.
A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER.
The ability of a substrate to retain an electrical charge.
A voltage-gated potassium channel that is expressed primarily in the HEART.
Methods to induce and measure electrical activities at specific sites in the heart to diagnose and treat problems with the heart's electrical system.
A major class of calcium-activated potassium channels that are found primarily in excitable CELLS. They play important roles in the transmission of ACTION POTENTIALS and generate a long-lasting hyperpolarization known as the slow afterhyperpolarization.
Compounds based on N-phenylacetamide, that are similar in structure to 2-PHENYLACETAMIDES. They are precursors of many other compounds. They were formerly used as ANALGESICS and ANTIPYRETICS, but often caused lethal METHEMOGLOBINEMIA.
Potassium channels where the flow of K+ ions into the cell is greater than the outward flow.
Drugs that block nerve conduction when applied locally to nerve tissue in appropriate concentrations. They act on any part of the nervous system and on every type of nerve fiber. In contact with a nerve trunk, these anesthetics can cause both sensory and motor paralysis in the innervated area. Their action is completely reversible. (From Gilman AG, et. al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed) Nearly all local anesthetics act by reducing the tendency of voltage-dependent sodium channels to activate.
The part of the brain that connects the CEREBRAL HEMISPHERES with the SPINAL CORD. It consists of the MESENCEPHALON; PONS; and MEDULLA OBLONGATA.
A family of membrane proteins that selectively conduct SODIUM ions due to changes in the TRANSMEMBRANE POTENTIAL DIFFERENCE. They typically have a multimeric structure with a core alpha subunit that defines the sodium channel subtype and several beta subunits that modulate sodium channel activity.
A highly variable species of the family Ranidae in Canada, the United States and Central America. It is the most widely used Anuran in biomedical research.
The output neurons of the cerebellar cortex.
Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum.
A meshlike structure composed of interconnecting nerve cells that are separated at the synaptic junction or joined to one another by cytoplasmic processes. In invertebrates, for example, the nerve net allows nerve impulses to spread over a wide area of the net because synapses can pass information in any direction.
A branch of the tibial nerve which supplies sensory innervation to parts of the lower leg and foot.
A voltage-gated sodium channel subtype found widely expressed in neurons of the central and peripheral nervous systems. Defects in the SCN8A gene which codes for the alpha subunit of this sodium channel are associated with ATAXIA and cognitive deficits.
A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.
Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.
Mature contractile cells, commonly known as myocytes, that form one of three kinds of muscle. The three types of muscle cells are skeletal (MUSCLE FIBERS, SKELETAL), cardiac (MYOCYTES, CARDIAC), and smooth (MYOCYTES, SMOOTH MUSCLE). They are derived from embryonic (precursor) muscle cells called MYOBLASTS.
Act of eliciting a response from a person or organism through physical contact.
A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.
A calcium channel blocker that is a class IV anti-arrhythmia agent.
Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)
A neuromuscular blocker and active ingredient in CURARE; plant based alkaloid of Menispermaceae.
A benzoate-cevane found in VERATRUM and Schoenocaulon. It activates SODIUM CHANNELS to stay open longer than normal.
A family of hexahydropyridines.
A family of delayed rectifier voltage-gated potassium channels that share homology with their founding member, KCNQ1 PROTEIN. KCNQ potassium channels have been implicated in a variety of diseases including LONG QT SYNDROME; DEAFNESS; and EPILEPSY.
3 beta,5,14-Trihydroxy-19-oxo-5 beta-card-20(22)-enolide. The aglycone cardioactive agent isolated from Strophanthus Kombe, S. gratus and other species; it is a very toxic material formerly used as digitalis. Synonyms: Apocymarin; Corchorin; Cynotoxin; Corchorgenin.
A specialized field of physics and engineering involved in studying the behavior and properties of light and the technology of analyzing, generating, transmitting, and manipulating ELECTROMAGNETIC RADIATION in the visible, infrared, and ultraviolet range.
A phylum of the kingdom Metazoa. Mollusca have soft, unsegmented bodies with an anterior head, a dorsal visceral mass, and a ventral foot. Most are encased in a protective calcareous shell. It includes the classes GASTROPODA; BIVALVIA; CEPHALOPODA; Aplacophora; Scaphopoda; Polyplacophora; and Monoplacophora.
Peripheral AFFERENT NEURONS which are sensitive to injuries or pain, usually caused by extreme thermal exposures, mechanical forces, or other noxious stimuli. Their cell bodies reside in the DORSAL ROOT GANGLIA. Their peripheral terminals (NERVE ENDINGS) innervate target tissues and transduce noxious stimuli via axons to the CENTRAL NERVOUS SYSTEM.
Antiarrhythmic agent pharmacologically similar to LIDOCAINE. It may have some anticonvulsant properties.
Chemicals that bind to and remove ions from solutions. Many chelating agents function through the formation of COORDINATION COMPLEXES with METALS.
The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx).
A subgroup of cyclic nucleotide-regulated ION CHANNELS of the superfamily of pore-loop cation channels that are opened by hyperpolarization rather than depolarization. The ion conducting pore passes SODIUM, CALCIUM, and POTASSIUM cations with a preference for potassium.
Treatment process involving the injection of fluid into an organ or tissue.
A delayed rectifier subtype of shaker potassium channels that is commonly mutated in human episodic ATAXIA and MYOKYMIA.
Venoms from snakes of the family Elapidae, including cobras, kraits, mambas, coral, tiger, and Australian snakes. The venoms contain polypeptide toxins of various kinds, cytolytic, hemolytic, and neurotoxic factors, but fewer enzymes than viper or crotalid venoms. Many of the toxins have been characterized.
Lanthanum. The prototypical element in the rare earth family of metals. It has the atomic symbol La, atomic number 57, and atomic weight 138.91. Lanthanide ion is used in experimental biology as a calcium antagonist; lanthanum oxide improves the optical properties of glass.
A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.
The study of the electrical activity and characteristics of the HEART; MYOCARDIUM; and CARDIOMYOCYTES.
Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.
Clusters of neuronal cell bodies in invertebrates. Invertebrate ganglia may also contain neuronal processes and non-neuronal supporting cells. Many invertebrate ganglia are favorable subjects for research because they have small numbers of functional neuronal types which can be identified from one animal to another.
A species of the family Ranidae occurring in a wide variety of habitats from within the Arctic Circle to South Africa, Australia, etc.
A group of cardiac arrhythmias in which the cardiac contractions are not initiated at the SINOATRIAL NODE. They include both atrial and ventricular premature beats, and are also known as extra or ectopic heartbeats. Their frequency is increased in heart diseases.
Ganglia of the sympathetic nervous system including the paravertebral and the prevertebral ganglia. Among these are the sympathetic chain ganglia, the superior, middle, and inferior cervical ganglia, and the aorticorenal, celiac, and stellate ganglia.
The excitable plasma membrane of a muscle cell. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)
A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine's most notable pharmacological effect is as a central nervous system stimulant, increasing alertness and producing agitation. It also relaxes SMOOTH MUSCLE, stimulates CARDIAC MUSCLE, stimulates DIURESIS, and appears to be useful in the treatment of some types of headache. Several cellular actions of caffeine have been observed, but it is not entirely clear how each contributes to its pharmacological profile. Among the most important are inhibition of cyclic nucleotide PHOSPHODIESTERASES, antagonism of ADENOSINE RECEPTORS, and modulation of intracellular calcium handling.
Semidomesticated variety of European polecat much used for hunting RODENTS and/or RABBITS and as a laboratory animal. It is in the subfamily Mustelinae, family MUSTELIDAE.
A species of the family Ranidae (true frogs). The only anuran properly referred to by the common name "bullfrog", it is the largest native anuran in North America.
The number of times the HEART VENTRICLES contract per unit of time, usually per minute.
The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.

Further evidence that prostaglandins inhibit the release of noradrenaline from adrenergic nerve terminals by restriction of availability of calcium. (1/21346)

1 Guinea-pig vasa deferentia were continuously superfused after labelling the transmitter stores with [3H](-)-noradrenaline. Release of [3H]-(-)-noradrenaline was induced by transmural nerve stimulation. 2 Prostglandin E2 (14 nM) drastically reduced the release of [3H]-(-)-noradrenaline, while tetraethylammonium (2 mM), rubidium (6 mM), phenoxybenzamine (3 muM) each in the presence or absence of Uptake 1 or 2 blockade, and prolonged pulse duration (from 0.5 to 2.0 ms) all significantly increased the release of [3H]-(-)-noradrenaline per nerve impulse. 3 The inhibitory effect of prostaglandin E2 on evoked release of [3H]-(-)-noradrenaline was significantly reduced by tetraethylammonium, rubidium and prolonged pulse duration, whilst it was actually enhanced by phenoxybenzamine. This indicates that increased release of noradrenaline per nerve impulse does not per se counteract the inhibitory effect of prostaglandin E2. 4 It is concluded that tetraethylammonium, rubidium and prolonged pulse duration counteracted the inhibitory effect of prostaglandin E2 on T3H]-(-)-noradrenaline release by promoting calcium influx during the nerve action potential. The results are consistent with, and add more weight to the view that prostaglandins inhibit the release of noradrenaline by restriction of calcium availability.  (+info)

Effect of electrotonic potentials on pacemaker activity of canine Purkinje fibers in relation to parasystole. (2/21346)

Isolated false tendons excised form dog hearts were mounted in a three-chamber tissue bath. Isotonic sucrose solution was perfused in the central chamber to provide a region of depressed conductivity between the fiber segments in chambers 1 and 3, which were perfused with Tyrode's solution. The electrotonic influence of spontaneous or driven responses evoked in chamber 3 during the first half of the spontaneous cycle of a chamber 1 peacemaker delayed the next spontaneous discharge. This effect changed to acceleration when the chamber 3 segment fired during the second half of the spontaneous cycle. We found that subthreshold depolarizing current pulses 50-300 msec applied across the sucrose gap caused similar degrees of delay or acceleration. Furthermore, hyperpolarizing currents caused the reverse pattern. The results indicate that the discharge pattern of a parasystolic focus may be altered by the electrotonic influence of activity in the surrounding tissue. The significance of these findings is considered in relation to the mechanism of production of parasystolic rhythms.  (+info)

Low resting potential and postnatal upregulation of NMDA receptors may cause Cajal-Retzius cell death. (3/21346)

Using in situ patch-clamp techniques in rat telencephalic slices, we have followed resting potential (RP) properties and the functional expression of NMDA receptors in neocortical Cajal-Retzius (CR) cells from embryonic day 18 to postnatal day 13, the time around which these cells normally disappear. We find that throughout their lives CR cells have a relatively depolarized RP (approximately -50 mV), which can be made more hyperpolarized (approximately -70 mV) by stimulation of the Na/K pump with intracellular ATP. The NMDA receptors of CR cells are subjected to intense postnatal upregulation, but their similar properties (EC50, Hill number, sensitivity to antagonists, conductance, and kinetics) throughout development suggest that their subunit composition remains relatively homogeneous. The low RP of CR cells is within a range that allows for the relief of NMDA channels from Mg2+ blockade. Our findings are consistent with the hypothesis that CR cells may degenerate and die subsequent to uncontrolled overload of intracellular Ca2+ via NMDA receptor activation by ambient glutamate. In support of this hypothesis we have obtained evidence showing the protection of CR cells via in vivo blockade of NMDA receptors with dizocilpine.  (+info)

Activity-dependent metaplasticity of inhibitory and excitatory synaptic transmission in the lamprey spinal cord locomotor network. (4/21346)

Paired intracellular recordings have been used to examine the activity-dependent plasticity and neuromodulator-induced metaplasticity of synaptic inputs from identified inhibitory and excitatory interneurons in the lamprey spinal cord. Trains of spikes at 5-20 Hz were used to mimic the frequency of spiking that occurs in network interneurons during NMDA or brainstem-evoked locomotor activity. Inputs from inhibitory and excitatory interneurons exhibited similar activity-dependent changes, with synaptic depression developing during the spike train. The level of depression reached was greater with lower stimulation frequencies. Significant activity-dependent depression of inputs from excitatory interneurons and inhibitory crossed caudal interneurons, which are central elements in the patterning of network activity, usually developed between the fifth and tenth spikes in the train. Because these interneurons typically fire bursts of up to five spikes during locomotor activity, this activity-dependent plasticity will presumably not contribute to the patterning of network activity. However, in the presence of the neuromodulators substance P and 5-HT, significant activity-dependent metaplasticity of these inputs developed over the first five spikes in the train. Substance P induced significant activity-dependent depression of inhibitory but potentiation of excitatory interneuron inputs, whereas 5-HT induced significant activity-dependent potentiation of both inhibitory and excitatory interneuron inputs. Because these metaplastic effects are consistent with the substance P and 5-HT-induced modulation of the network output, activity-dependent metaplasticity could be a potential mechanism underlying the coordination and modulation of rhythmic network activity.  (+info)

Ionic currents underlying spontaneous action potentials in isolated cerebellar Purkinje neurons. (5/21346)

Acutely dissociated cell bodies of mouse Purkinje neurons spontaneously fired action potentials at approximately 50 Hz (25 degrees C). To directly measure the ionic currents underlying spontaneous activity, we voltage-clamped the cells using prerecorded spontaneous action potentials (spike trains) as voltage commands and used ionic substitution and selective blockers to isolate individual currents. The largest current flowing during the interspike interval was tetrodotoxin-sensitive sodium current (approximately -50 pA between -65 and -60 mV). Although the neurons had large voltage-dependent calcium currents, the net current blocked by cobalt substitution for calcium was outward at all times during spike trains. Thus, the electrical effect of calcium current is apparently dominated by rapidly activated calcium-dependent potassium currents. Under current clamp, all cells continued firing spontaneously (though approximately 30% more slowly) after block of T-type calcium current by mibefradil, and most cells continued to fire after block of all calcium current by cobalt substitution. Although the neurons possessed hyperpolarization-activated cation current (Ih), little current flowed during spike trains, and block by 1 mM cesium had no effect on firing frequency. The outward potassium currents underlying the repolarization of the spikes were completely blocked by 1 mM TEA. These currents deactivated quickly (<1 msec) after each spike. We conclude that the spontaneous firing of Purkinje neuron cell bodies depends mainly on tetrodotoxin-sensitive sodium current flowing between spikes. The high firing rate is promoted by large potassium currents that repolarize the cell rapidly and deactivate quickly, thus preventing strong hyperpolarization and restoring a high input resistance for subsequent depolarization.  (+info)

Somatic recording of GABAergic autoreceptor current in cerebellar stellate and basket cells. (6/21346)

Patch-clamp recordings were performed from stellate and basket cells in rat cerebellar slices. Under somatic voltage clamp, short depolarizing pulses were applied to elicit action potentials in the axon. After the action potential, a bicuculline- and Cd2+-sensitive current transient was observed. A similar response was obtained when eliciting axonal firing by extracellular stimulation. With an isotonic internal Cl- solution, the peak amplitude of this current varied linearly with the holding potential, yielding an extrapolated reversal potential of -20 to 0 mV. Unlike synaptic or autaptic GABAergic currents obtained in the same preparation, the current transient had a slow rise-time and a low variability between trials. This current was blocked when 10 mM BAPTA was included in the recording solution. In some experiments, the current transient elicited axonal action potentials. The current transient was reliably observed in animals aged 12-15 d, with a mean amplitude of 82 pA at -70 mV, but was small and rare in the age group 29-49 d. Numerical simulations could account for all properties of the current transient by assuming that an action potential activates a distributed GABAergic conductance in the axon. The actual conductance is probably restricted to release sites, with an estimated mean presynaptic current response of 10 pA per site (-70 mV, age 12-15 d). We conclude that in developing rats, stellate and basket cell axons have a high density of GABAergic autoreceptors and that a sizable fraction of the corresponding current can be measured from the soma.  (+info)

Inducible genetic suppression of neuronal excitability. (7/21346)

Graded, reversible suppression of neuronal excitability represents a logical goal of therapy for epilepsy and intractable pain. To achieve such suppression, we have developed the means to transfer "electrical silencing" genes into neurons with sensitive control of transgene expression. An ecdysone-inducible promoter drives the expression of inwardly rectifying potassium channels in polycistronic adenoviral vectors. Infection of superior cervical ganglion neurons did not affect normal electrical activity but suppressed excitability after the induction of gene expression. These experiments demonstrate the feasibility of controlled ion channel expression after somatic gene transfer into neurons and serve as the prototype for a novel generalizable approach to modulate excitability.  (+info)

Cerebellar Purkinje cell simple spike discharge encodes movement velocity in primates during visuomotor arm tracking. (8/21346)

Pathophysiological, lesion, and electrophysiological studies suggest that the cerebellar cortex is important for controlling the direction and speed of movement. The relationship of cerebellar Purkinje cell discharge to the control of arm movement parameters, however, remains unclear. The goal of this study was to examine how movement direction and speed and their interaction-velocity-modulate Purkinje cell simple spike discharge in an arm movement task in which direction and speed were independently controlled. The simple spike discharge of 154 Purkinje cells was recorded in two monkeys during the performance of two visuomotor tasks that required the animals to track targets that moved in one of eight directions and at one of four speeds. Single-parameter regression analyses revealed that a large proportion of cells had discharge modulation related to movement direction and speed. Most cells with significant directional tuning, however, were modulated at one speed, and most cells with speed-related discharge were modulated along one direction; this suggested that the patterns of simple spike discharge were not adequately described by single-parameter models. Therefore, a regression surface was fitted to the data, which showed that the discharge could be tuned to specific direction-speed combinations (preferred velocities). The overall variability in simple spike discharge was well described by the surface model, and the velocities corresponding to maximal and minimal discharge rates were distributed uniformly throughout the workspace. Simple spike discharge therefore appears to integrate information about both the direction and speed of arm movements, thereby encoding movement velocity.  (+info)

article{ceee0ce3-7cdb-426b-8c17-2f62ad33a172, abstract = {,p,AIMS: To evaluate the usefulness of the signed value of monophasic action potential duration difference in analysing the cause of dispersion of ventricular repolarization.,/p,,p,METHODS AND RESULTS: Monophasic action potentials were simultaneously recorded from the right ventricular apex and outflow tract during programmed stimulation in 36 patients with ventricular arrhythmias. The time difference between the ends of repolarization on the two monophasic action potentials was used as a measure of the dispersion of ventricular repolarization, and the signed value of the monophasic action potential duration difference was used to specify the contributions of the activation time difference and the monophasic action potential duration difference to the dispersion of ventricular repolarization. During right ventricular pacing, single and double programmed stimulation and at the induction of ventricular arrhythmias, the dispersion of ...
Myocardial ischemia-reperfusion (IR) injury represents a constellation of pathological processes that occur when ischemic myocardium experiences a restoration of perfusion. Reentrant arrhythmias, which represent a particularly lethal manifestation of IR injury, can result when ischemic tissue exhibits decreased excitability and/or changes of action potential duration (APD), conditions that precipitate unidirectional conduction block. Many of the cellular components that are involved with IR injury are modulated by pH and/or phosphometabolites such as ATP and phosphocreatine (PCr), all of which can be manipulated in vivo and potentially in the clinical setting. Using a mathematical model of the cardiomyocyte that we previously developed to study ischemia and reperfusion, we performed a series of simulations with the aim of determining whether pH- or phosphometabolite-related processes play a more significant role in generating changes in excitability and action potential morphology that are associated
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Home , Papers , TREK-1 and TRAAK Are Principal K Channels at the Nodes of Ranvier for Rapid Action Potential Conduction on Mammalian Myelinated Afferent Nerves. ...
The combination of the ATCHI stain and microelectrode impalements has shown that the distribution of the RBB and Purkinje fibers of the mouse conduction system is, in general, similar to that reported in other species.14,15 However, in the mouse strain investigated (Swiss Webster), we found that the RBB was, very frequently, intimately associated with the septal artery in the right ventricle and could be visualized under bright field as white fibers running along the artery in base to apex direction. Our investigation provides the first available data on the action potential properties of the murine His-Purkinje system.. Several of the electrophysiological characteristics presented in this study are consistent with data from Purkinje cells from other species.15,32 In one of these studies, action potential properties of Purkinje cells were profiled in cow, sheep, and canine.32 The freshly isolated cells had a maximum diastolic potential of −70 and −85 mV, upstroke velocity of 150 to 750 V/s, ...
Antibodies for proteins involved in positive regulation of voltage-gated potassium channel activity involved in ventricular cardiac muscle cell action potential repolarization pathways, according to their Panther/Gene Ontology Classification
Fingerprint Dive into the research topics of Selective Effects of Potassium Elevations on Glutamate Signaling and Action Potential Conduction in Hippocampus. Together they form a unique fingerprint. ...
The regulation of a K(+) current activating during oscillatory electrical activity (I(K,slow)) in an insulin-releasing beta-cell was studied by applying the perforated patch whole-cell technique to intact mouse pancreatic islets. The resting whole-cell conductance in the presence of 10 mM glucose amounted to 1.3 nS, which rose by 50 % during a series of 26 simulated action potentials. Application of the K(ATP)-channel blocker tolbutamide produced uninterrupted action potential firing and reduced I(K,slow) by approximately 50 %. Increasing glucose from 15 to 30 mM, which likewise converted oscillatory electrical activity into continuous action potential firing, reduced I(K,slow) by approximately 30 % whilst not affecting the resting conductance. Action potential firing may culminate in opening of K(ATP) channels by activation of ATP-dependent Ca(2+) pumping as suggested by the observation that the sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor thapsigargin (4 microM) inhibited I(K,slow) by
This question shows a good amount of intuition. It is true that the signal is generally thought to diffuse passively. However, active propagation of dendritic signals is certainly an important property. As opposed to the axon, where the action potential is generated by voltage-gated sodium (Na+) channels, in the dendrites, the voltage gated channels are calcium (Ca2+) channels (VGCC -- voltage gated calcium channels) or non-specific cation (Na+, K+, and Ca2+) channels such as the NMDA channel. The voltage gated nature of these excitatory channels leads to a positive feedback effect similar to that of the action potential itself. However, the time course of these signals is much slower: on the order of 10s to 100s of milliseconds, as opposed to the 1ms time scale of the action potential. These dendritic spikes or calcium spikes or plateau potentials can lead to firing of bursts of action potentials. As a side point, action potentials generated in the soma can actually be propagated backwards ...
This directory contains the Neuron source code for cortical Layer 5 pyramidal cell model and experiments employed in: Distinct Contributions of Na(V)1.6 and Na(V)1.2 in Action Potential Initiation and Backpropagation Wenqin Hu, Cuiping Tian, Tun Li, Mingpo Yang, Han Hou & Yousheng Shu (2009) Nat Neurosci 12(8): 996-1002. Part of model is based on: Mainen, Z. F. and Sejnowski, T. J. Nature 382: 363-6 (1996) Yu, Y., Shu, Y., et al. J Neurosci 28: 7260-72 (2008) Shu, Y., Hasenstaub, A., et al. Nature 441: 761-5. (2006) =============================================== BRIEF OVERVIEW OF THE CONTENTS Three different but related models are involved in this package: 1). A realistic model of Layer 5 pyramidal cell with sophisticatedly described voltage-dependent sodium channels at the axon initial segment. Either action potentials initiation site (figure not shown in the aforementioned paper, see its main text) or backpropagation failure threshold (Supplementary Fig.4 and Fig.8) can be tested here. This ...
A single action potential can travel down the axon. It does not exist at multiple points on the axon at the same time. The active part of the HH model describes the generation of an action potential at a single point. The passive part describes how the action potential travels down the axon. The main problem of passive travel is that the action potential dies down (after one space constant, the action potential will be very small). So nodes of Ranvier have to be spaced much shorter than the space constant in order to regenerate the amplitude of the action potential ...
Squid giant axons internally perfused with a 30 mM NaF solution and bathed in a 100 mM CaCl2 solution, which are known to produce long lasting action potentials in response to pulses of outward current, were investigated. The effects of tetrodotoxin (TTX) and of tetraethylammonium ion (TEA+) on such action potentials were studied. The results are summarized as follows: (a) An addition of 1--3 microM TTX to the external solution altered but did not block the action potentials; it increased the height of the action potential by approximately 15 mV, and it decreased the membrane conductance as the peak of excitation by about two-thirds. (b) Voltage-clamp experiments performed with both NaCl and TTX in the external CaCl2 solution revealed that the TTX-insensitive action potential does not involve a rise in gNa, whereas the experiments performed without TTX showed that the action potential is accompanied by a large rise in gNa. (c) Internally applied TEA+ was shown to selectively block the ...
Sodium entry during an action potential determines the energy efficiency of a neuron. The classic Hodgkin-Huxley model of action potential generation is notoriously inefficient in that regard with about 4 times more charges flowing through the membrane than the theoretical minimum required to achieve the observed depolarization. Yet, recent experimental results show that mammalian neurons are close to the optimal metabolic efficiency and that the dynamics of their voltage-gated channels is significantly different than the one exhibited by the classic Hodgkin-Huxley model during the action potential. Nevertheless, the original Hodgkin-Huxley model is still widely used and rarely to model the squid giant axon from which it was extracted. Here, we introduce a novel family of Hodgkin-Huxley models that correctly account for sodium entry, action potential width and whose voltage-gated channels display a dynamics very similar to the most recent experimental observations in mammalian neurons. We speak ...
Definition of action current in the Legal Dictionary - by Free online English dictionary and encyclopedia. What is action current? Meaning of action current as a legal term. What does action current mean in law?
Cardiac electrical alternans, characterized by a beat-to-beat alternation in action potential waveform, is a naturally occurring phenomenon, which can occur at sufficiently fast pacing rates. Its presence has been putatively linked to the onset of cardiac reentry, which is a precursor to ventricular fibrillation. Previous studies have shown that closed-loop alternans control techniques that apply a succession of externally administered cycle perturbations at a single site provide limited Show moreCardiac electrical alternans, characterized by a beat-to-beat alternation in action potential waveform, is a naturally occurring phenomenon, which can occur at sufficiently fast pacing rates. Its presence has been putatively linked to the onset of cardiac reentry, which is a precursor to ventricular fibrillation. Previous studies have shown that closed-loop alternans control techniques that apply a succession of externally administered cycle perturbations at a single site provide limited ...
Acute myocardial ischemia is implicated in many cases of fatal arrhythmias.1 2 The basis of ischemic arrhythmogenesis is alteration in the electrical properties of ventricular tissue, leading to changes in action potential conduction.3 4 Altered electrical properties are a result of the pathophysiological conditions of ischemia, which directly affect membrane ionic currents and intracellular and extracellular ionic concentrations.5 6 Therefore, there exist cause-and-effect relationships between ischemia modification of membrane currents and ionic concentrations and ischemia-related changes in action potential conduction. We investigated these cause-and-effect relationships to determine the ionic mechanisms of depressed conduction and development of conduction block during acute ischemia.. Our investigative tool is a theoretical multicellular fiber model that accounts for the major conditions of ischemia at the level of individual ionic currents and concentrations. The fiber is composed of LRd ...
Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na+ and K+ channels, with generator potential and graded potential models lacking voltage-gated Na+ channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na+ channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a footprint in the generator potential that obscures incoming signals. These three processes reduce information rates by ~50% in generator potentials, to ~3 times that of ...
In this work, detailed computational models are used to study the electrophysiology of normal epicardium and the arrhythmogenic effects of epicardial cell remodeling post-infarction. The canine epicardial myocyte model described here reproduces a wide range of experimentally observed rate dependent phenomena in cell and tissue. Model behavior depends on updated formulations for the 4-AP sensitive transient outward current: Ito1), the slow component of the delayed rectifier potassium current: IKs), the L-type Ca2+ channel: ICa,L) and the sodium-potassium pump: INaK) fit to data from canine ventricular myocytes. The model shows that Ito1 plays a limited role in potentiating peak ICa,L and Ca2+ release for propagated action potentials: APs), but modulates the time course of action potential duration: APD) restitution. IKs plays an important role in APD shortening at short diastolic intervals but a limited role in AP repolarization at longer cycle lengths. In addition, simulations demonstrate that ICa,L,
1. Simultaneous measurements of action potential and resistance and of action current and impedance change have been made at a single node of Ranvier.. 2. There is a parallelism between action potential, action current, and resistance change measured at a node of Ranvier.. 3. Some implications of these results have been discussed in relation to the corresponding data obtained from the squid giant axon.. ...
Corticotroph releasing hormone (CRH) is one of the major regulatory hormones associated with the neuroendocrine response to stress. Pituitary corticotroph cells generate repetitive action potentials and associated Ca2+ transients in response to the agonist CRH. The mechanisms underlying this process are complex. CRH is known to activate the adenosine 3,5-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) pathway. PKA phosphorylates L-type voltage-sensitive Ca2+ channels, activating them and contributing to the generation of an action potential and Ca2+ transients. In an earlier Hodgkin-Huxley type mathematical model of this process, LeBeau et al. showed than an increase in the L-type current was sufficient to generate repetitive action potentials from a resting state in the model (LeBeau et al., 1997). However, they found that the action potential frequency of the model was much higher than the observed experimental action potential frequency. This problem was addressed in the ...
Precise spike coordination between the spiking activities of multiple neurons is suggested as an indication of coordinated network activity in active cell assemblies. Spike correlation analysis aims to identify such cooperative network activity by detecting excess spike synchrony in simultaneously recorded multiple neural spike sequences. Cooperative activity is expected to organize dynamically during behavior and cognition; therefore currently available analysis techniques must be extended to enable the estimation of multiple time-varying spike interactions between neurons simultaneously. In particular, new methods must take advantage of the simultaneous observations of multiple neurons by addressing their higher-order dependencies, which cannot be revealed by pairwise analyses alone. In this paper, we develop a method for estimating time-varying spike interactions by means of a state-space analysis. Discretized parallel spike sequences are modeled as multi-variate binary processes using a ...
Previous studies have reported that enhanced antiarrhythmic effects occur when agents that prolong repolarization are combined with agents that block the sodium channels. The mechanism(s) of this interaction have not been elucidated. In this study, the interactions between the prolongation of action potential duration (APD) by a potassium channel blocker and the reduction in the maximal upstroke velocity of phase 0 of action potential (Vmax) by sodium channel blockers were investigated in guinea pig papillary muscle using conventional microelectrode techniques. Agents that produce selective electrophysiologic effects were chosen, including low concentrations of barium chloride (BaCl2), which selectively blocks the inwardly rectifying potassium current without effects on other repolarizing or depolarizing currents, O-demethyl-encainide (ODME), which blocks the activated sodium channel with slow onset/offset kinetics, and mexiletine, which preferentially blocks the inactivated sodium channel with ...
In this simulation action potential initiation, action potential properties and the role of axon initial segment Na+ channels are investigated in a realistic model of a layer 5 pyramidal neuron axon initial segment. The main Na+ channel properties were constrained by experimental data and the axon initial segment was reconstructed. Model parameters were constrained by direct recordings at the axon initial segment ...
The action potential is fundamental to information processing in the brain. Neurons fire action potentials in response to a variety of inputs and action potentials exist in many different shapes, sizes and frequencies. In this course we will begin with a study of ion channels, the membrane bound biochemical switches that give the action potential its shape. Then we will explore the numerous factors that influence the nature of an individual action potential: neuronal morphology, ion channel composition, and intracellular signaling cascades. We will conclude by considering how circuits of diverse neuronal phenotypes integrate synaptic signals, which give rise to sophisticated information processing, learning and memory, and psychiatric disease. Student projects will explore how ion channel abnormalities, so-called channelopathies, influence cognition and behavior.. ...
Summary To understand how the brain works, tools need to be developed that will allow neuroscientists to investigate how interactions between individual neurons lead to emergent networks. Towards this goal, we will develop targetable voltage sensing nanorods that self-insert into the cell membrane and optically and non-invasively record action potentials at the single particle and nanoscale level, at multiple sites and across a large field-of-view. In semiconductors, absorption and emission band edges are modulated by an external electric field, even more so when optically excited electron-hole pairs are confined, giving rise to the quantum confined Stark effect. The physical origin of this effect is in the separation of photoexcited charges, creating a dipole that opposes the external field. The proposed sensors will optically record action potential with unique advantages not offered by other methods: much larger voltage sensitivity, high brightness, and hence single-particle voltage ...
In neurophysiology, several mathematical models of the action potential have been developed, which fall into two basic types. The first type seeks to model the experimental data quantitatively, i.e., to reproduce the measurements of current and voltage exactly. The renowned Hodgkin-Huxley model of the axon from the Loligo squid exemplifies such models. Although qualitatively correct, the H-H model does not describe every type of excitable membrane accurately, since it considers only two ions (sodium and potassium), each with only one type of voltage-sensitive channel. However, other ions such as calcium may be important and there is a great diversity of channels for all ions. As an example, the cardiac action potential illustrates how differently shaped action potentials can be generated on membranes with voltage-sensitive calcium channels and different types of sodium/potassium channels. The second type of mathematical model is a simplification of the first type; the goal is not to reproduce ...
The reliability and temporal precision of signal propagation between neurons is a major constraint for different coding strategies in neuronal networks. In systems that rely on rate coding, input-output functions of neurons are classically described as ratios of mean firing rates, and the precise timing of individual action potentials is not considered a meaningful parameter (Shadlen and Newsome, 1994, 1998). In these systems, synchrony of presynaptic action potentials and reliable synaptic transmission have even been implicated to deteriorate the information content of the postsynaptic spike train (Zador, 1998). For the functioning of a temporal code in neuronal networks, on the other hand, the precision and reliability of synaptic integration is a prerequisite (Abeles, 1991; Konig et al., 1996; Mainen and Sejnowski, 1995; Nowak et al., 1997; Roy and Alloway, 2001), and without exact spike timing in the millisecond range, synchronous activity among neurons that putatively form a functional cell ...
Using the injury potential method, researchers found that certain cells, classified as excitable, suffered sudden and transitory alterations in resting potential, with later return to the initial value (Fig. 1-B). This cycle was named cellular action potential. In 1883, Burdon-Sanderson and Page 2 obtained continuous recordings of the potentials generated by frog cardiac beats. In one of their observations, when an electrode was placed on the intact surface of the heart and another on an injured region, transitory monophasic potential (only one polarity) was recorded in opposition to the known transitory multiphase recordings (positive and negative polarities). This was the origin of the term monophasic action potential (MAP), whose form was very similar to the cellular action potential later obtained by the cellular impalement technique with microelectrodes (IT). In the late 19th century, it was already known that the electric currents generated in each cardiac beat could be detected on the ...
Whole-cell patch-clamp recordings were obtained using Multiclamp 700B patch amplifiers (Molecular Devices), and data were analyzed using pClamp 10 software (Molecular Devices). To characterize basic membrane properties, a series of hyperpolarizing and depolarizing current steps were applied for 500 ms in 10-45 pA increments at 5 s intervals. The action potential threshold was determined for the first spike at the lowest level of depolarizing current required to evoke at least one spike. Action potential spike measurements were taken from the first action potential on the first sweep to reach the threshold. Spike height was measured as the peak membrane voltage relative to threshold, and half-width was measured at the half amplitude of the action potential. Input resistance was determined from the slope of the linear regression taken through the voltage-current relationship in the hyperpolarizing range.. To determine connectivity among C4- and C8-projecting cell populations, simultaneous ...
ABSTRACT: A mathematical model of the cardiac ventricular action potential is presented. In our previous work, the membrane Na+ current and K+ currents were formulated. The present article focuses on processes that regulate intracellular Ca2+ and depend on its concentration. The model presented here for the mammalian ventricular action potential is based mostly on the guinea pig ventricular cell. However, it provides the framework for modeling other types of ventricular cells with appropriate modifications made to account for species differences. The following processes are formulated: Ca2+ current through the L-type channel (ICa), the Na(+)-Ca2+ exchanger, Ca2+ release and uptake by the sarcoplasmic reticulum (SR), buffering of Ca2+ in the SR and in the myoplasm, a Ca2+ pump in the sarcolemma, the Na(+)-K+ pump, and a nonspecific Ca(2+)-activated membrane current. Activation of ICa is an order of magnitude faster than in previous models. Inactivation of ICa depends on both the membrane voltage ...
The cardiac cell action potential, like action potentials in nerves, is divided into five phases, numbered 0 through 4. Two of these, phase 2 (the plateau phase) and phase 4 (the diastolic interval) are marked by little to no change in voltage. Sodium, potassium and calcium are the primary ions.
Mechanisms of action potential (AP) generation in neocortical pyramidal cells have been the focus of intense experimental and theoretical research over the last several decades. It has proven very difficult, however, to arrive at a consensus model which can satisfactorily account for all of its features. One of the still unresolved issues is lack of accurate description of Na+ channel kinetics in different neuronal compartments. Here, we measured kinetics of somatic Na+ channels using high temporal resolution (5-10 kHz, −3dB, low pass four-pole Bessel filter) cell-attached recordings from layer 5 pyramidal neurons in neocortical slices. The data were described by fitting different Markov models with differential evolution fit algorithms. The limited speed of voltage steps and the effect of current filtering were accounted for in the fit procedure. Hodgkin-Huxley-type models which assumed a number of independent activation gates were not the optimal description of the experimentally recorded ...
ABSTRACT: We have developed a detailed mathematical model for Ca handling and ionic currents in the human ventricular myocyte. Our aims were to: (1) simulate basic excitation-contraction coupling phenomena; (2) use realistic repolarizing K current densities; (3) reach steady-state. The model relies on the framework of the rabbit myocyte model previously developed by our group, with subsarcolemmal and junctional compartments where ion channels sense higher [Ca] vs. bulk cytosol. Ion channels and transporters have been modeled on the basis of the most recent experimental data from human ventricular myocytes. Rapidly and slowly inactivating components of I(to) have been formulated to differentiate between endocardial and epicardial myocytes. Transmural gradients of Ca handling proteins and Na pump were also simulated. The model has been validated against a wide set of experimental data including action potential duration (APD) adaptation and restitution, frequency-dependent increase in Ca transient ...
Action potentials in cardiac myocytes have durations in the order of magnitude of 100 milliseconds. In biomedical investigations the documentation of the occurrence of action potentials is often not sufficient, but a recording of the shape of an action potential allows a functional estimation of several molecular players. Therefore a temporal resolution of around 500 images per second is compulsory. In the past such measurements have been performed with photometric approaches limiting the measurement to one cell at a time. In contrast, imaging allows reading out several cells at a time with additional spatial information. Recent developments in camera technologies allow the acquisition with the required speed and sensitivity. We performed action potential imaging on isolated adult cardiomyocytes of guinea pigs utilizing the fluorescent membrane potential sensor di-8-ANEPPS and latest electron-multiplication CCD as well as scientific CMOS cameras of several manufacturers. Furthermore, we ...
The combination of the rapid and large voltage changes during action potentials and the large sodium current density in Purkinje neurons required careful tuning of the voltage-clamp circuitry for series resistance compensation, as well as reduction of the sodium current to reduce errors arising from imperfect compensation.. A particular concern was whether the overall system, including the partially compensated resistance of the pipette in series with the cell capacitance, allows faithful imposition of voltage using the very narrow spike waveforms of Purkinje neurons, which can have widths at half-amplitude of about 200 μs. In previous experiments (Carter and Bean 2009), we did control experiments using a second electrode to record intracellular voltage while a cell was voltage clamped with a spike waveform. These experiments showed that the action potential command voltage was accurately imposed on the cell membrane, with measured voltage at the peak of the action potential differing from the ...
Elezgarai I, Diez J, Puente N, Azkue JJ, Benitez R, Bilbao A, Knopfel T, Donate-Oliver F & Grandes P (2003). Subcellular localization of the voltage-dependent potassium channel Kv3. 1b in postnatal and adult rat medial nucleus of the trapezoid body. Neuroscience 118, 889-898 ...
Spike correlations between neurons are ubiquitous in cortex, but their role is at present not understood. Here we describe the firing response of a leaky integrate-and-fire neuron when it receives a temporarily correlated input generated by pre-synaptic correlated neuronal populations. Input correlations are characterized in terms of the firing rates, Fano factors, correlation coefficients and correlation time scale of the neurons driving the target neuron. It has been shown [1] that the sum of the pre-synaptic spike trains cannot be well described by a Poisson process. In fact, the total current has a non-trivial two-point correlation function described by two main parameters: the correlation time scale (how precise the input correlations are in time), and the correlation magnitude (how strong they are). Therefore, the total current generated by the input spike trains cannot be approximated by a white noise Gaussian process in the diffusion limit. Instead, the total current is replaced by a ...
This experiment deals with the basic principles behind sodium ion channels in neurons and their effects on action potentials or spikes, how gating properties regulate channel behavior and influence firing.
A method was developed to non-invasively and simultaneously track individual action-potentials propagating across multiple branches of identified neurons in neocortical cultures.
With just-suprathreshold current pulses, FS cells often displayed a considerable delay before the first spike, whereas GIN cells did not (cf. Fig. 2, C and D, top panels). In addition, GIN cells often displayed an afterdepolarization (ADP) following low-frequency action potentials (Fig. 2C, inset; cf. Halabisky et al. 2006). At higher levels of stimulus current, spike frequency adaptation was evident in GIN cells (Fig. 2D, bottom), but not in FS cells (Fig. 2D, bottom). Finally, at higher stimulus currents, the peak of the first action potential in GIN cells was the most positive in the train and the trough of the first afterhyperpolarization (AHP) was the most negative (Fig. 2C, bottom). By contrast, the action potential heights and AHP magnitudes of FS cells changed little under similar conditions (Fig. 2D, bottom). The firing of GIN cells also differed from that of RS cells, whose second action potential peak was substantially more negative than the first and whose first AHP was the most ...
Animal models of dorsal root ganglion (DRG) neurons are widely used in pain research as in vitro models of human nociception, due to a lack of human-specific alternatives. However, these models do not capture human-specific electrophysiology, including differences in ion channel function, and do not address significant inter-neuronal variability, e.g. differences in ion channel expression and action potential morphology between DRG neuron sub-types. This heterogeneity is difficult to address through experiments alone but can result in variable responses to therapies and disease.. We have developed a method for integrating biological variability with in silico modelling, using experimentally-calibrated populations of models, and have used this approach extensively in cardiac electrophysiology. We propose integrating new recordings of human DRG neuron electrophysiology, provided by our collaboration with Anabios Corporation,with our methodology to construct and validate populations of in silico ...
ABSTRACT: BACKGROUND: Computational biology is a powerful tool for elucidating arrhythmogenic mechanisms at the cellular level, where complex interactions between ionic processes determine behavior. A novel theoretical model of the canine ventricular epicardial action potential and calcium cycling was developed and used to investigate ionic mechanisms underlying Ca2+ transient (CaT) and action potential duration (APD) rate dependence. METHODS AND RESULTS: The Ca2+/calmodulin-dependent protein kinase (CaMKII) regulatory pathway was integrated into the model, which included a novel Ca2+-release formulation, Ca2+ subspace, dynamic chloride handling, and formulations for major ion currents based on canine ventricular data. Decreasing pacing cycle length from 8000 to 300 ms shortened APD primarily because of I(Ca(L)) reduction, with additional contributions from I(to1), I(NaK), and late I(Na). CaT amplitude increased as cycle length decreased from 8000 to 500 ms. This positive rate-dependent property ...
Thomas, N, Dupont, E, Halliday, D, Fry, CH and Severs, NJ (2006) An inducible cell system to investigate connexin co-expression and action potential propagation within the heart In: 28th Annual International-Society-for-Heart-Research North American Section Meeting, 2006-06-13 - 2006-06-16, Toronto, CANADA. Full text not available from this repository ...
A long-standing hypothesis is that action potentials initiate first in the axon hillock/initial segment (AH-IS) region because of a locally high density of Na+ channels. We tested this idea in subicular pyramidal neurons by using patch-clamp recordings in hippocampal slices. Simultaneous recordings from the soma and IS confirmed that orthodromic action potentials initiated in the axon and then invaded the soma. However, blocking Na+ channels in the AH-IS with locally applied tetrodotoxin (TTX) did not raise the somatic threshold membrane potential for orthodromic spikes. TTX applied to the axon beyond the AH-IS (30-60 μm from the soma) raised the apparent somatic threshold by ∼8 mV. We estimated the Na+ current density in the AH-IS and somatic membranes by using cell-attached patch-clamp recordings and found similar magnitudes (3-4 pA/μm2). Thus, the present results suggest that orthodromic action potentials initiate in the axon beyond the AH-IS and that the minimum threshold for spike ...
Thank you, Dr. Ferber- but let me clarify my question- Were making current clamp recordings, and injecting square current pulses whilst in current clamp. Our amplifier seems to turn off capacitance/series resistance compensation in current clamp mode, though Im not so sure. In our preparation, a strong inward rectifying current is expected to be seen in medium spiny neurons by applying hyperpolarizing pulses. Weve been applying 20 pA steps from 0 to -1nA (the maximum current injection possible for our amplifier), yet we do not see any inward rectification. Inward rectification is a defining characteristic of medium spiny neurons. These cells have been labelled iontophoretically with neurobiotin, and we see that they are indeed medium spiny neurons. Weve checked our intracellular and ACSF ionic concentrations against what others are using, and find no great difference. The cell fires what appear to be normal action potentials with depolarizing pulses in current clamp. Im thinking that ...
Get this from a library! Potassium channels for high-frequency action potential generation in GABAergic interneurons of rat hippocampus. [Cheng-Chang Lien;]
Definition of inexcitable in the Legal Dictionary - by Free online English dictionary and encyclopedia. What is inexcitable? Meaning of inexcitable as a legal term. What does inexcitable mean in law?
TY - JOUR. T1 - Effects of acetylcholine on action potential characteristics of atrial and ventricular myocardium after bilateral cervical vagotomy in the cat.. AU - Kovacs, R. J.. AU - Bailey, J. C.. PY - 1985/4. Y1 - 1985/4. N2 - Acetylcholine, the parasympathetic neurotransmitter, shortens the action potential duration of cat atrial muscle cells, but not ventricular muscle cells. In mammalian species, atrial tissue receives a richer cholinergic nerve supply than ventricular tissue. To determine whether chronic withdrawal of cholinergic tone might influence the subsequent response of these tissues to cholinergic stimulation, we examined the effect of acetylcholine on the action potentials of atrial and ventricular myocytes from cats with intact vagi and cats after chronic bilateral cervical vagotomy. Following bilateral cervical vagotomy, physostigmine (10(-6) M) failed to alter atrial tension development or action potential duration. Acetylcholine produced shortening of the action potential ...
Here I demonstrate how to use a single microcontroller pin to generate action-potential-like waveforms. The output is similar my fully analog action potential generator circuit, but the waveform here is created in an entirely different way. A microcontroller is at the core of this project and determines when to fire action potentials. Taking advantage of the pseudo-random number generator (rand() in AVR-GCCs stdlib.h), I am able to easily produce unevenly-spaced action potentials which more accurately reflect those observed in nature. This circuit has a potentiometer to adjust the action potential frequency (probability) and another to adjust the amount of overshoot (afterhyperpolarization, AHP). I created this project because I wanted to practice designing various types of action potential measurement circuits, so creating an action potential generating circuit was an obvious perquisite. The core of this circuit is a capacitor which is charged and discharged by toggling a microcontroller pin ...
The compound muscle action potential (CMAP) or compound motor action potential is an electromyography investigation (electrical study of muscle function). The CMAP idealizes the summation of a group of almost simultaneous action potentials from several muscle fibers in the same area. These are usually evoked by stimulation of the motor nerve. Patients that suffer from critical illness myopathy, which is a frequent cause of weakness seen in patients in hospital intensive care units, have prolonged compound muscle action potential.[1]. ...
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Fig. 1 3DFG SEM imaging and optical characterization.. (A) SEM images of 5-μm 3DFG electrodes. Scale bars, 5 μm (I), 1 μm (II), and 0.5 μm (III). (B) UV-vis absorbance as a function of wavelength for fused silica (gray), 3DFG synthesized at 800°C for 10 min (red), and 3DFG synthesized at 800°C for 30 min (blue). (C) Real (ε1) and imaginary (ε2) parts of the dielectric constant of 3DFG in the visible and near-infrared range. (D) Photocurrent generated at the interface between 3DFG electrodes and PBS under excitation with ultrafast (picosecond) pulsed laser at 1064 nm at varying laser intensities. The pulse trains have a duration of 6 ms. (E) Capacitive and faradaic current components of the photocurrent generated by laser excitation. The capacitive values were taken as the maximum current peak at the onset of the laser excitation. The faradaic values were calculated as the average of the last 1-ms-long portion before the end of the laser pulse train. ...
The action potential (AP) is the basic signaling unit in various crucial physiological processing, for instance, in neurotransmission, muscle contraction, and glandular secretion (Koch, 1990). The classic model animal, Caenorhabditis elegans (or C. elegans), with a simple and compact nervous system, conservatively employs the calcium-mediated all-or-none APs for odor response in AWA olfactory neurons (Liu et al., 2018), as well as for muscle contraction in body wall muscles (Gao and Zhen, 2011; Liu et al., 2011) and pharyngeal muscles (Davis et al., 1999). Plateau potentials were also observed in ASE and RMD neurons (Goodman et al., 1998; Mellem et al., 2008; Lockery et al., 2009; Lockery and Goodman, 2009), though the underlying roles in specific behavior are still elusive. Either in neurons or in muscles, the action potential firing is dependent on the excitatory pre-synaptic vesicles release. The minimum number of the presynaptic vesicles to elicit a single action potential in C. elegans has ...
Ceballos, Cesar C., Antonio C. Roque, and Ricardo M. Leão. A negative slope conductance of the persistent sodium current prolongs subthreshold depolarizations. Biophysical journal 113.10 (2017): 2207-2217.
The secretory epithehum of the mantle of the clam Anomalocardia brasiliana is excitable. The ionic dependence of its action potentials was investigated. Two distinct phases could be recognized by their ionic dependences. The early spike phase, that appeared in all action potentials, was dependent on the Na+ concentration of the solution in the interstitial space and was insensitive to tetrodotoxin (TTX) at concentrations as high as 36μmol l−1. It was inhibited by local anesthetics, and its repolarization was inhibited by veratrine. The data show this electrogenesis is caused by TTX-insensitive sodium channels located at the basolateral membrane of this epithelium. Cardiac-like action potentials were recorded in several specimens: the rapid Na+-dependent spike was followed by a slower repolarization phase that formed a plateau and increased the action potential duration. The plateau amplitude was markedly increased when the external Ca2+ concentration was increased to (60 mmol l−1 and it was ...
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Supervisors: Ole Paulsen, Tanja Fuchsberger. Spike timing-dependent plasticity (STDP) is a physiologically relevant form of Hebbian learning, in which near coincident pre- and postsynaptic firing induces synaptic plasticity: Long term potentiation (LTP) is induced when the presynaptic spike precedes postsynaptic firing, and long term depression (LTD) when postsynaptic firing precedes the presynaptic spike [1]. However, these plasticity rules are profoundly influenced by neuromodulators [2]. Reward, novelty or surprise are correlated with neuromodulatory signals, such as dopamine, acetylcholine or noradrenaline, which modulate memories and behavioural outcome. They regulate STDP through various mechanisms, as they can control the biophysical properties of dendrites, including the dynamics of spike backpropagation, and can influence the state of kinases and phosphatases implicated in synaptic plasticity (Seol et al., 2007). In our laboratory we recently demonstrated a retroactive effect of ...
TY - JOUR. T1 - Layer-specific high-frequency action potential spiking in the prefrontal cortex of awake rats. AU - Boudewijns, Z.S.R.M.. AU - Groen, M.R.. AU - Lodder, B.N.. AU - McMaster, M.T.. AU - Kaleogrades, L.. AU - de Haan, R.. AU - Narayanan, R.T.. AU - Meredith, R.M.. AU - Mansvelder, H.D.. AU - de Kock, C.P.J.. PY - 2013. Y1 - 2013. N2 - Cortical pyramidal neurons show irregular in vivo action potential (AP) spiking with high frequency bursts occurring on sparse background activity. Somatic APs can backpropagate from soma into basal and apical dendrites and locally generate dendritic calcium spikes. The critical AP frequency for generation of such dendritic calcium spikes can be very different depending on cell-type or brain area involved. Previously, it was shown in vitro that calcium electrogenesis can also be induced in L(ayer) 5 pyramidal neurons of prefrontal cortex (PFC). It remains an open question whether somatic burst spiking and the resulting dendritic calcium electrogenesis ...
We correlated primary T wave changes with the changes of monophasic action potentials (MAP) recorded with suction electrodes from the ventricular surface of the dog heart following systemic or intracoronary infusions of small doses of isoproterenol (ISP). The portions of the heart perfused with ISP were excised and weighed to determine the mass of perfused tissue. ISP shortened the ventricular MAP by an average of 12-18 msec in the entire ventricular mass following systemic administration, in 34 plus or minus 6 per cent of the ventricular mass after injection into the left circumflex coronary artery (LCA), in 8.5 plus or minus 2.6% of the ventricular mass after injection into a branch of LCA and in 17 plus or minus 8 per cent of the ventricular mass after injection into the right CA. The MAP changes induced by ISP were similar to the transmembrane action potential changes recorded with microelectrodes from papillary muscles excised from the same dogs. The most important results of this study ...
Rhythmic patterns of neuronal activity have been found at multiple levels of various sensory systems. In the olfactory bulb or the antennal lobe, oscillatory activity exhibits a broad range of frequencies and has been proposed to encode sensory information. However, the neural mechanisms underlying …
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TY - JOUR. T1 - Learning-induced afterhyperpolarization reductions in hippocampus are specific for cell type and potassium conductance. AU - de Jonge, M. C.. AU - Black, J.. AU - Deyo, R. A.. AU - Disterhoft, J. F.. PY - 1990/5. Y1 - 1990/5. N2 - Hippocampal slices were prepared from rabbits trained in a trace eye-blink conditioning task and from naive and pseudoconditioned controls. Measurements of the post-burst afterhyperpolarization (AHP), action potential, and other cellular properties were obtained from intracellular recordings of CA1 pyramidal (N=49) and dentate gyrus granule cells (N=52). A conditioning-specific reduction in the amplitude of the AHP was found in CA1 cells but not in dentate granule cells. This reduction in the AHP was apparent at 50 ms after the end of a depolarizing current pulse, and was maintained for at least 650 ms. Other measured cell characteristics (input resistance, resting membrane potential, action potential shape, inward rectification, spike threshold) were ...
Kv3 voltage-gated potassium channels (Kv3.1-4) are activated by depolarization of the neuronal plasma membrane to potentials above -20 mV; they open rapidly during the depolarising phase of the neuronal action potential to initiate repolarisation and prevent sodium channel inactivation. As the neuron begins to repolarise, the channels deactivate quickly and so do not contribute significantly to the after-hyperpolarisation [xii] [xiii]. These distinct properties allow the channels to terminate the action potential rapidly without compromising action potential threshold, rise time, or magnitude, and without increasing the duration of the refractory period that follows. Consequently, neurons expressing Kv3 channels can sustain action potential firing at high frequencies [xiv]. Kv3.1-3 subtypes are expressed mainly in the central nervous system, whereas Kv3.4 channels are predominant in skeletal muscle and sympathetic neurons [xv]. Kv3.1-3 channel subtypes are differentially expressed in ...
From some sources, Ive read that excitatory postsynaptic potentials (EPSPs) decay over time, which would imply that they arent abolished by action potentials. However, other sources seem to indicate the opposite (although I may be misunderstanding them). Plus, the classical leaky-integrate-and-fire neuron model implies that EPSPs are abolished by action potentials (although this could well be a simplification). Does the refractory period of an action potential affect its originating EPSP? Or is it a separate phenomenon?. ...
Derivation of a new force field for crystal-structure prediction using global optimization: nonbonded potential parameters for hydrocarbons and alcohols
Sinoatrial nodal cells (SANCs) generate spontaneous action potentials (APs) that control the cardiac rate. The brain modulates SANC automaticity, via the autonomic nervous system, by stimulating membrane receptors that activate (adrenergic) or inactivate (cholinergic) adenylyl cyclase (AC). However, these opposing afferents are not simply additive. We showed that activation of adrenergic signaling increases AC-cAMP/PKA signaling, which mediates the increase in the SANC AP firing rate (i.e., positive chronotropic modulation). However, there is a limited understanding of the underlying internal pacemaker mechanisms involved in the crosstalk between cholinergic receptors and the decrease in the SANC AP firing rate (i.e., negative chronotropic modulation). We hypothesize that changes in AC-cAMP/PKA activity are crucial for mediating either decrease or increase in the AP firing rate and that the change in rate is due to both internal and membrane mechanisms. In cultured adult rabbit pacemaker cells infected
Intracellular recordings were obtained from rat neocortical neurons in vitro. The current-voltage-relationship of the neuronal membrane was investigated using current- and single-electrode-voltage-clamp techniques. Within the potential range up to 25 mV positive to the resting membrane potential (RMP: -75 to -80 mV) the steady state slope resistance increased with depolarization (i.e. steady state inward rectification in depolarizing direction). Replacement of extracellular NaCl with an equimolar amount of choline chloride resulted in the conversion of the steady state inward rectification to an outward rectification, suggesting the presence of a voltage-dependent, persistent sodium current which generated the steady state inward rectification of these neurons. Intracellularly injected outward current pulses with just subthreshold intensities elicited a transient depolarizing potential which invariably triggered the first action potential upon an increase in current strength. ...
can be generated along the axon while the threshold potential is reached. The greater the strength of the stimulus, causing the membrane depolarisation process to occur. Subsequently, some [[Sodium_voltage-gated_ion_channels,voltage-gated Na,sup,+,/sup, channels]] are opened, allowing the [[Sodium,Na,sup,+,/sup,]] ions to move across the membrane into the intracellular environment. The neuronal membrane now becomes slightly positive, relative to the outside of membrane. As the membrane potential shift from -70 mV to more positive value, the threshold potential is reached, causing all of the voltage-gated Na+ channel to open, creating a rapid rise of membrane potential value into the maximum, +60 mV. During depolarisation, the membrane potential value would not exceed the amount of +60mV as it is the equilibrium potential of Na,sup,+,/sup, ,ref,http://people.eku.edu/ritchisong/301notes2.htm,/ref ...
Studies on isolated inside-out patches have revealed that the pancreatic α-cells paradoxically contain a high density of KATP channels (14). In the pancreatic β-cells, glucose inhibits the KATP channels and thus leads to stimulation of electrical activity and insulin secretion (33,34). Yet, if closure of KATP channels in β-cells results in stimulation of insulin secretion, how can closure of the same channels in α-cells inhibit glucagon secretion? We have proposed that the answer to this conundrum lies in the distinct electrophysiological properties of the α- and β-cells (Fig. 6; see also Fig. 2). Thus, whereas β-cell electrical activity and secretion are principally dependent on L-type Ca2+ channels, α-cell action potential firing involves voltage-gated Na+ channels. Unlike the L-type Ca2+ channels, the Na+ channels undergo voltage-dependent inactivation (i.e., they enter a nonconducting state when the voltage becomes too positive) (7). Closure of the KATP channels with resultant ...
We have evaluated an intracardiac technique for the study of the electrophysiological patterns of early or subendocardial ischaemia in man. Simultaneous recordings of the paced endocardial evoked response and monophasic action potentials were obtained during pacing stress testing in 10 patients with reversible myocardial ischaemia. Early patterns of change occurred in both these recordings in response to regional ischaemia. Abnormal rate corrected shortening of the local repolarisation time in the paced endocardial evoked response from the left ventricular ischaemic zone diverging from control non-ischaemic values by a mean of 10.6% was paralleled by decreases in the simultaneous paced monophasic action potentials duration. A differential delay in the local activation time and conduction was also documented by the paced endocardial evoked response and monophasic action potential electrodes. Non-ischaemic control zones showed no changes in the pattern of activation and repolarisation. Disparate ...
Spontaneous activation and contraction of the heart are a consequence of the specialized pacemaking tissue in these anatomic locales. As described in Chap. 238, action potentials in the heart are regionally heterogeneous. The action potentials in cells isolated from nodal tissue are distinct from those recorded from atrial and ventricular myocytes (Fig. 239-1). The complement of ionic currents present in nodal cells results in a less negative resting membrane potential compared with atrial or ventricular myocytes. Electrical diastole in nodal cells is characterized by slow diastolic depolarization (phase 4), which generates an action potential as the membrane voltage reaches threshold. The action potential upstrokes (phase 0) are slow compared with atrial or ventricular myocytes, being mediated by calcium rather than sodium current. Cells with properties of SA and AV nodal tissue are electrically connected to the remainder of the myocardium by cells with an electrophysiologic phenotype between ...
The basal forebrain (BF) has long been implicated in attention, learning and memory, and recent studies have established a causal relationship between artificial BF activation and arousal. However, neural ensemble dynamics in the BF still remains unclear. Here, recording neural population activity in the BF and comparing it with simultaneously recorded cortical population under both anesthetized and unanesthetized conditions, we investigate the difference in the structure of spontaneous population activity between the BF and the auditory cortex (AC) in mice. The AC neuronal population show a skewed spike rate distribution, a higher proportion of short (≤80 ms) inter-spike intervals (ISIs) and a rich repertoire of rhythmic firing across frequencies. Although the distribution of spontaneous firing rate in the BF is also skewed, a proportion of short ISIs can be explained by a Poisson model at short time scales (≤20 ms) and spike count correlations are lower compared to AC cells, with optogenetically
p,Transduction of graded synaptic input into trains of all-or-none action potentials (spikes) is a crucial step in neural coding. Hodgkin identified three classes of neurons with qualitatively different analog-to-digital transduction properties. Despite widespread use of this classification scheme, a generalizable explanation of its biophysical basis has not been described. We recorded from spinal sensory neurons representing each class and reproduced their transduction properties in a minimal model. With phase plane and bifurcation analysis, each class of excitability was shown to derive from distinct spike initiating dynamics. Excitability could be converted between all three classes by varying single parameters; moreover, several parameters, when varied one at a time, had functionally equivalent effects on excitability. From this, we conclude that the spike-initiating dynamics associated with each of Hodgkins classes represent different outcomes in a nonlinear competition between oppositely ...
In this video, I want to talk about how action potentials are generated the trigger zone and how theyre conducted down the axon. So Ive drawn a soma here in red and one axon in green. And Ive blown up the axon to a very large size just so I had some room to draw. Heres our graph of the membrane potential on the y-axis and time on the x-axis. And now Ive put a couple of different kinds of ion channels in the membrane of the axon. The first in this lighter grey are the leak channels that we talked about when we talked about the neuron resting potential. These channels are open all the time. Theyre not gated. And I have not drawn any ligand gated ion channels like the neurotransmitter receptors that occur on the soma and the dendrites. But to talk about the action potential, I need to introduce an entirely new type of channel that Ive drawn in dark grey with this little v. And these are voltage gated ion channels. The membrane of an axon as many voltage gated ion channels, most of which open ...
The invention relates to an apparatus and method for monitoring cells and to a method for monitoring changes in cells upon addition of an analyte to the cells environment, comprising a device which includes an array of microelectrodes disposed in a cell culture chamber, upon which array a portion of cells adhere to the surfaces of the microelectrodes. The diameter of the cells are larger than the diameters of the microelectrodes. A voltage signal is applied across each of the microelectrodes and a reference electrode. Detection and monitoring of the signals resulting from the application of the voltage signal provides information regarding the electrical characteristics of the individual cells, including impedance (combined cell membrane capacitance and conductance), action potential parameters, cell membrane capacitance, cell membrane conductance, and cell/substrate seal resistance. Such an invention is useful in detecting or screening a variety of biological and chemical agents.
TY - JOUR. T1 - VERFAHREN ZUR BESTIMMUNG DER MECHANISCHEN AKTIVITAT UND DER ELEKTROPHYSIOLOGISCHEN EIGENSCHAFTEN ISOLIERTER MENSCHLICHER EMBRYONALER HERZEN. AU - Resch, B. A.. AU - Papp, J.. PY - 1982. Y1 - 1982. N2 - The authors have invented a complex method by which to examine surviving hearts of early human embryos. The method enables testing of mechanical activity of the heart as well as of many electrophysiological parameters, such as spontaneous heart rate, electrical threshold of stimuli, stimulus conduction time, effective refractory phase, and intracellular action potential. A special transport device was designed for storage and movement of embryonic hearts which were all obtained from cases of legal abortion. A contractility recorder was advised to follow up mechanical heart activity. A variant of the standard micro-electrode technique was developed to measure electrophysiological parameters. This technique has worked extremely well in recording the membrane potential at rest and the ...
TY - JOUR. T1 - GABAergic inhibition shapes frequency adaptation of cortical activity in a frequency-dependent manner. AU - Heistek, Tim S.. AU - Lodder, Johannes C.. AU - Brussaard, Arjen B.. AU - Bosman, Laurens W. J.. AU - Mansvelder, Huibert D.. PY - 2010/3/19. Y1 - 2010/3/19. KW - Short-term plasticity. KW - Neuronal network. KW - GABA. KW - Voltage-sensitive dye imaging. KW - Benzodiazepine. U2 - 10.1016/j.brainres.2010.01.047. DO - 10.1016/j.brainres.2010.01.047. M3 - Article. C2 - 20114035. VL - 1321. SP - 31. EP - 39. JO - Brain Research. JF - Brain Research. SN - 0006-8993. ER - ...
Cortical neurons exhibit highly irregular inter-spike intervals (ISIs) [1]. Differences in irregularity could be in part due to imbalances of excitatory and inhibitory inputs to the neurons, which determines the statistics of the net input [2]. There is experimental evidence that the intrinsic irregularity of neurons in the awake monkey is constant [3]. However, changes in irregularity have also been reported [4, 5] in different cortical areas and different behavioral tasks. The classical measure of spike time irregularity is the coefficient of variation (CV), a global measure defined as the dispersion of the ISIs. However, the CV largely overestimates the irregularity in the case of pronounced changes in firing rate. This led several researchers to propose alternative measures of irregularity that are local in time and therefore relatively independent of rate changes. To our knowledge, these measures have never been compared to each other. Here we compare four such measures: the local ...
Action potential[edit]. An action potential is a spike of both positive and negative ionic discharge that travels along the ... The creation and conduction of action potentials represents a fundamental means of communication in the nervous system. Action ... The action potential travels from one location in the cell to another, but ion flow across the membrane occurs only at the ... As a result, the action potential signal jumps along the axon, from node to node, rather than propagating smoothly, as they do ...
Potential Mechanisms of Action[edit]. The manufacturer of AHCC states that the culturing process utilized in its manufacture ... The compound is a subject of research as a potential anti-cancer agent but has not been conclusively found to treat cancer or ... The mechanism of action of AHCC is poorly understood and there is little known about its safety.[2] As of 2011[update] clinical ...
Isolation of the action potential[edit]. The first recorded time of isolating a single action potential was carried out by ... The magnitude of the action potential set up in any single nerve fibre is independent of the strength of the exciting stimulus ... If that stimulus exceeds the threshold potential, the nerve or muscle fiber will give a complete response; otherwise, there is ... Stimuli too weak to produce a spike do, however, set up a local electrotonus, the magnitude of the electronic potential ...
Action potentials. Nerve fiber analysis. Awards. Nobel Prize for Physiology or Medicine (1944). Foreign Member of the Royal ... and recipient of the Nobel Prize for Physiology or Medicine in 1944 for his work with action potentials in nerve fibers while ... summarizing their investigations into the actions of human nerve cells. This work led to their recognition in 1944, when they ...
... decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire ... an action potential). Some neurons also generate subthreshold membrane potential oscillations. These signals are generated and ... the neuron generates an all-or-nothing electrochemical pulse called an action potential. This potential travels rapidly along ... When an action potential reaches the axon terminal, it opens voltage-gated calcium channels, allowing calcium ions to enter the ...
The four commonly recognized propagation methods include action potentials (APs), variation potentials (VPs), local electric ... These action potentials can influence processes such as actin-based cytoplasmic streaming, plant organ movements, wound ... Pickard BG (1973). "Action Potentials in Higher Plants". Botanical Review. 39 (2): 172-201. doi:10.1007/BF02859299. JSTOR ... APs allow for the movement of signaling ions and molecules from the pre-potential cell to the post-potential cell(s). These ...
... into action potentials or graded potentials. This process is called sensory transduction. The cell bodies of the sensory ... The first action potential occurs in the retinal ganglion cell. This pathway is the most direct way for transmitting visual ... A tonic receptor is a sensory receptor that adapts slowly to a stimulus and continues to produce action potentials over the ... These sensory neurons produce action potentials. Their axons form the olfactory nerve, and they synapse directly onto neurons ...
Okamura Y, Murata Y, Iwasaki H (February 2009). "Voltage-sensing phosphatase: actions and potentials". The Journal of ... this activity seems to become apparent at high membrane potentials, at lower potentials the 5'-phosphatase activity is ... Changes in membrane potential therefore move the S4 back and forth through the membrane, allowing the voltage sensor to act ... Therefore, the action of VSPs is to indirectly regulate processes dependent on phospholipids. The main substrate that has been ...
When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be ... Some neurons emit action potentials constantly, at rates of 10-100 per second, usually in irregular patterns; other neurons are ... These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth ... Barnett, MW; Larkman, PM (2007). "The action potential". Practical Neurology. 7 (3): 192-197. PMID 17515599. Shepherd, Gordon M ...
... is their ability to send action potentials back into the dendritic arbor. Known as back-propagating action potentials, these ... a train of back-propagating action potentials artificially generated at the soma can induce a calcium action potential (a ... returning the electrochemical gradient to the resting potential. After an action potential has occurred, there is a transient ... An action potential propagates the electrical activity along the membrane of the neuron's dendrites to the cell body and then ...
The activated motor neurons then transmit their signals, via action potential, to motor neurons in the legs. However, when a ... Barnett MW, Larkman PM, Larkman (2007). "The action potential". Pract Neurol. 7 (3): 192-7. PMID 17515599.. ... Almodovar CR, Lambrechts D, Mazzone M, Carmeliet P (2009). "Role and Therapeutic Potential of VEGF in the Nervous System". ...
In action potentials stimulated on the epicardium, it was found that the duration of the action potential needed to be 40-60 ... The repolarization phase of an action potential initially results in hyperpolarization, attainment of a membrane potential, ... the action potential predictably widens. The Kv3 channels open at a more positive membrane potential and deactivate 10 times ... allowing more potassium to flow through after the resting membrane potential has been reached. Following the action potential, ...
While there is ample evidence to prove the existence of backpropagating action potentials, the function of such action ... Instead, only when the soma depolarizes enough from accumulating graded potentials and firing an axonal action potential will ... as an action potential was triggered, its dendritic echo could enter the dendrite and potentially trigger a second action ... "Backpropagating action potentials in neurones: measurement, mechanisms and potential functions". Prog Biophys Mol Biol. 87 (1 ...
Goel's pieces were Excitatory response; action potential and aspiration. Goel portrays human-human, human-animal and human- ... action potential (2005) aspiration (2005) Wading in the Water: The work of Kelsey Stephenson co-written with Stephanie C. Kane ...
"Action Potential on Vimeo". Vimeo.com. 22 December 2016. Retrieved 19 May 2020. "Magik Door". Magikdoor.net. Retrieved 19 May ...
... once an action potential is initiated, there is a period of time that a new action potential cannot be initiated. This is ... depolarization in the current cell as it has to refract back to phase 4 of the action potential before a new action potential ...
Action potential (2005). *. Amanita phalloides (2007). *Apophallation (2010). *. Archaea. *Balance disorder (2019) ...
There, he and Huxley managed to insert a fine cannula into the giant axon of squids and record action potentials from inside ... They proposed that the characteristic shape of the action potential is caused by changes in the selective permeability of the ... Together with Richard Keynes he demonstrated that in addition to the changes in permeability that lead to an action potential ... After establishing ion movements across a selectively permeable cell membrane as the mechanism of the action potential, Hodgkin ...
Pharmacology The drug tetrodotoxin (TTX) blocks action potentials at extremely low concentrations. The site of action of TTX on ... "A comparison of the Hodgkin-Huxley model and the Soliton theory for the Action Potential in Nerves " Action Waves in the Brain ... thus propagating the action potential. The transmembrane potential is restored by delayed opening of potassium channels. ... Yet, action potentials are present at 0 °C. The time course is slowed in a manner predicted by the measured opening and closing ...
This blocks action potentials and slows neural function. Histrionicotoxin has been shown to bind competitively with many local ... studies of the effects of histrionicotoxin on end-plate potential have shown that the compound hinders membrane potential ... Masukawa LM, Albuquerque EX (September 1978). "Voltage- and time-dependent action of histrionicotoxin on the endplate current ...
ISBN 978-0-87901-041-6. Irving Langmuir (1916). "The Relation Between Contact Potentials and Electrochemical Action". ... While a solar cell has an electric field that results from a contact potential (see contact potentials and solar cells), this ... Voltage difference is not the same as potential difference. The potential difference between two points A and B is independent ... This electric field is created from a built-in potential, which arises from the contact potential between the two different ...
As with the action potentials that follow them, LTS vary little in amplitude or shape at different holding potentials. This ... The spike is typically crowned by a burst of two to seven action potentials, which is known as a low-threshold burst. LTS are ... An excitatory postsynaptic potential (EPSP) opens the channels, thus generating a LTS. The LTS triggers Na+-dependent action ... LTS result in the neuron reaching the threshold for an action potential. LTS is a large depolarization due to an increase in ...
The solution was that nerve impulses, or action potentials, do not travel down the core of the fiber, but rather along the ... In 1952, they published their theory of how action potentials are transmitted in a joint paper, in which they also describe one ... Their eventual discovery of the basis for propagation of nerve impulses (called an action potential) earned them the Nobel ... In 1952, having completed work on action potentials, Huxley was teaching physiology at Cambridge and became interested in ...
Active baroreceptors fire action potentials ("spikes") more frequently. The greater the stretch the more rapidly baroreceptors ... Baroreceptor action potentials are relayed to the solitary nucleus, which uses frequency as a measure of blood pressure. ... fire action potentials. Many individual baroreceptors are inactive at normal resting pressures and only become activated when ... The ability of baroreflex activation therapy to reduce sympathetic nerve activity suggests a potential in the treatment of ...
Action potentials would become prolonged by the toxin. This action mechanism is expected based on the structure of the toxin, ... Based on affected channel subtypes, LmαTX5 could be expected to cause cardiac arrhythmia, by altering action potential ... Catterall, William A. (10 December 1977). "Activation of the action potential Na+ ionophore by neurotoxins. An allosteric model ... and inhibition of action potential propagation in neurons and skeletal muscles leading to paralysis of the prey. Ruiming, Zhao ...
Inactivation only occurs in neurons firing action potentials; this means that drugs that modulate fast inactivation selectively ... This inactivation prevents the channel from opening, helping end the action potential. Many antiepileptic drugs, like ... slow the recovery from inactivation and hence reduce the ability of neurons to fire action potentials. ... In a study conducted to assess the teratogenic potential of AEDs in the zebrafish embryo, the teratogenicity index of ...
Contact or injury that causes leaflets to deform, will trigger an action potential. The action potential travels through the ... On receiving the action potential signal, the cells in the lower half of the pulvinus respond by expelling potassium and ... Mycologists have discovered action potentials in fungi but it is not currently clear whether they have any significance to ... Investigators have observed an action potential and changes in leaf turgor that accompany the reflex; they trigger the rapid ...
Voltage-gated potassium channels are also uniporters that can be found in neurons and are essential for action potentials. This ... OpenStax College (2013). Chapter 12.4 The Action Potential. OpenStax College. pp. 523-531. ISBN 1938168135. Alberts, Bruce et ... the channels open which depolarizes the membrane which leads to the action potential being sent down the membrane. Antiporter ...
Normally, the action potential impulse will spread through the heart quickly enough that each cell will respond only once. ... All of the cells in the heart have the ability to initiate an action potential; however, only some of these cells are designed ... Shen, H; Choe, W (April 2011). "Spontaneous high-frequency action potential". Science China Life Sciences. 54 (4): 311-35. doi: ... Tachyarrhythmias are the result of spontaneous action potentials arise from cardiac muscle cells. Cardiac arrhythmia is often ...
"Membrane Potential and Action Potential". From Molecules to Networks. Elsevier. pp. 351-376. doi:10.1016/b978-0-12-397179- ... creating an action potential. Membrane transporter "Membrane Channels". Cell Biology. Elsevier. 2017. pp. 261-284. doi:10.1016/ ... which produces the resting potential in living cells. Whether or not a membrane is polarized is determined by the distribution ...
Though successful in predicting the timing and qualitative features of the action potential, it nevertheless failed to predict ... Huxley developed the voltage clamp and created the first biophysical model of the action potential. Hubel & Wiesel discovered ... "Simulation of alcohol action upon a detailed Purkinje neuron model and a simpler surrogate model that runs ,400 times faster" ...
The third pillar funds potential solutions to social and economic problems, "Societal challenges" (SC). ... The specific objectives and actions vary between funding periods. In FP6 and FP7 focus was still in technological research, in ... IMPETUS contributes by investigating potential microservices that serve the airspace user's needs in all phases of the ...
Years later, she would enumerate a set of proper procedures concerning the delivery of potential heirs, perhaps informed by the ... and could pursue any legal action as any "single unmarried person might or may do at any time", despite still being married.[44 ... and was looking to secure his son's future by betrothing him to a conveniently wealthy ward whose children could be potential ...
Implement usage limitations when the Fish and Wildlife service express a potential adverse effect on a particular species based ... taking action against those for which the risks outweighed the benefits.[8] In 1988, Congress amended the pesticide ... Section 16 allows for a judicial review process for individuals or entities affected by an EPA order or action.[3] ... The amendments required the EPA to assess potential risks the pesticides posed to humans, the environment, and wildlife and ...
On 8 May 2018, the United States withdrew from the Joint Comprehensive Plan of Action with Iran, reinstating Iran sanctions ... Some scientists and local residents have raised concerns about the potential effect of Poland's LNG infrastructure on marine ...
Ultimately, each action by the other member is countered with a matching response, competition with competition and cooperation ... An agent using this strategy will first cooperate, then subsequently replicate an opponent's previous action. If the opponent ... An agent using this strategy will first cooperate, then subsequently replicate an opponent's previous action. If the opponent ...
Gurib-Fakim, A.; Mahomoodally, M. F.. African Flora as Potential Sources of Medicinal Plants : Towards the Chemotherapy of ... comparable to insulin action in vitro.». British journal of biomedical science. ... Traditional Medicinal Herbs and Food Plants Have the Potential to Inhibit Key Carbohydrate Hydrolyzing Enzymes In Vitro and ...
It is of utmost importance to arrest his potential for mischief, for he is the prime mover and can easily set tools, one to ... is the free habit of free and healthy national thought and action and that it was impossible in a state of servitude.[36] He ...
A single radioligand can be used this way to test many potential drug candidates for the same target. A related technique ... Much more commonly, drug occupancy at a purported site of action can be inferred indirectly by competition studies between ... or into molecules that bind to receptors or other sites of drug action. Such labelled compounds are known as radiotracers. PET ... a potential biomarker for Alzheimer's) in the brain. ...
In CS pacemakers, NE increases only the amplitude of the depolarizing drive potential and the number of action potentials ... which allows neurons to intrinsically fire action potentials at sub-threshold membrane potentials. Studies have shown that the ... L-type calcium channels are known to increase the frequency of action potentials in some neurons, which might be the reason ... There are several inward currents that help produce action potentials and bursts in pacemaker neurons. There are two main ...
"Status of State Action on the Medicaid Expansion Decision". The Henry J. Kaiser Family Foundation. April 5, 2018. Retrieved ... lottery enabled studies to accurately measure the impact of health insurance on an individual's health and eliminate potential ...
James Palace in order to pitch their ideas and to be connected with potential investors, mentors and business contacts.[58] The ... Prince Andrew's place on board and the possibility of the Queen's son being killed in action made the British Government ... "US lawyer takes legal action in Prince Andrew sex claim case", BBC News, 6 January 2015 ... Virginia Roberts made allegations of sexual impropriety against the Duke in court papers related to a civil action in Florida ...
... tolerability and potential modes of action". International Journal of Antimicrobial Agents (Review). 45 (2): 106-10. doi: ... Rasmusson GH (1986). Chemical Control of Androgen Action. Annual Reports in Medicinal Chemistry. 21. pp. 179-188. doi:10.1016/ ... Giltay EJ, Gooren LJ (2009). "Potential side effects of androgen deprivation treatment in sex offenders". The Journal of the ... Sieber MA, Hegel JK (November 2013). "Azelaic acid: Properties and mode of action". Skin Pharmacology and Physiology (Review). ...
Mechanisms of action[edit]. Rituximab mechanisms of action; the three major independent mechanisms are (1) antibody dependent ... A potential use for rituximab was identified by two Norwegian doctors who were treating people who had cancer with rituximab; ...
Failed libel action[edit]. In 1992, Tilton sued ABC for libel because of its investigation and report, but the case was ... citing the potential for the divorce settlement to be used to hide financial assets that were currently part of the many fraud ... the video's authors saw the market potential and began selling official copies of their creation. Similar videos have since ... cases; Richardson's petition to have the divorce action put on hold until after the fraud cases were settled was denied.[18] ...
The observation that the grass is wet has two potential explanations, "it rained" and "the sprinkler was on", which entail the ... However, only the second potential explanation, "the sprinkler was on", satisfies the integrity constraint. ... The potential solution of becoming a citizen by residence and naturalization fails because it violates the integrity constraint ...
It explores potential surfaces with modified antennules; once it has found a potentially suitable spot, it attaches head-first ... therefore it is more common for their shells to be ground up by wave action than for them to reach a depositional setting. ...
Saliva, which possesses both mechanical cleansing action and immunologic action, including salivary immunoglobulin A antibodies ... Another potential symptom is a metallic, acidic, salty or bitter taste in the mouth. The pseudomembranous type rarely causes ... Disruption to any of these local and systemic host defense mechanisms constitutes a potential susceptibility to oral ... strains of Candida with more adhesion capability have more pathogenic potential than other strains. The prevalence of Candida ...
The actions of aprepitant are said to be entirely central, thus requiring passage of the drug into the central nervous system.[ ... Substance P is a key first responder to most noxious/extreme stimuli (stressors), i.e., those with a potential to compromise ... Hesketh PJ (Jul 2001). "Potential role of the NK1 receptor antagonists in chemotherapy-induced nausea and vomiting". Supportive ... Rupniak NM (May 2002). "New insights into the antidepressant actions of substance P (NK1 receptor) antagonists". Canadian ...
Mechanisms of actionEdit. Rituximab mechanisms of action; the three major independent mechanisms are (1) antibody dependent ... This potential use was investigated after improvements in chronic fatigue syndrome was seen in two cancer patients treated with ...
As progress is made, other arms move ahead to repeat these actions and the original suckers detach. During crawling, the heart ... This form of locomotion allows these octopuses to move quickly away from a potential predator without being recognised.[76] A ... which show a variety of complex reflex actions that persist even when they have no input from the brain.[45] Unlike vertebrates ...
Mose, who sees potential in Daniel as an haute couture designer; much to the dismay of Mads, who wants his son to focus on ... This action almost cost him his marriage to Ingeborg. As his business grows, Mads, who's originally honest and well-meaning, is ... Stein, who works in her husband's bank, from the Nazi Jew-hunt, her character changes into a brave woman of action that starts ...
Although photoreceptors are neurons, they do not conduct action potentials with the exception of the photosensitive ganglion ... To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. ... Thus, the random opening or closing of sodium channels will not affect the membrane potential of the cell; only the closing of ... This change in the cell's membrane potential causes voltage-gated calcium channels to close. This leads to a decrease in the ...
Pharmacology is the study of drugs and their actions.. *Photobiology is the study of the interactions between non-ionizing ... It was under the Byzantines with physicians such of Theophilus Protospatharius that they realized the potential in uroscopy to ... Subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. ... and potential surgical candidates on the hospital wards. Surgery has many sub-specialties, including general surgery, ...
The only remaining potential airline for operating a hub was Air Berlin, which was in financial difficulties and did not plan ... The postponement led to the cancelling of moving plans and in some cases reversing actions already completed. It cited ... While Berlin has many "ghost stations" built in preparation for potential future construction, there is no provision underneath ... the new airport head presented the Schüßler plan as the course of action.[247] ...
Another group has tried to increase the levels of isoflavone, known for its potential cancer preventive properties, by ... "Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening". Journal of Experimental Botany. 53 (377 ...
... action was blocked by a court injunction that deemed the ballot illegal. Negotiations failed to stop strike action in March, BA ... The chairman of BOAC, Miles Thomas, was in favour of a merger as a potential solution to this disagreement and had backing for ... Industrial action by Mixed Fleet commenced in January 2017 after rejecting a pay offer.[110] Strike action continued throughout ... In 2005, wildcat action was taken by union members over a decision by Gate Gourmet not to renew the contracts of 670 workers ...
... which is the summation of action potentials over all electrodes in an MEA. This analysis yielded the conclusion that, in their ... quieted networks have little capacity for plasticity due to a diminished ability to create action potentials. A different and ...
The lure may require a specialised presentation to impart an enticing action as, for example, in fly fishing. A common way to ... It is generally believed that larger fish have a greater breeding potential. Some fisheries have a slot limit that allows the ... Slot limits are put in action to help protect certain fish in given area. They generally require anglers to release captured ...
"Lyme Disease Action. 15 December 2011. Archived from the original on 19 June 2013. Retrieved 15 December 2012.. ... White matter disease may have a greater potential for recovery than gray matter disease, perhaps because the neuronal loss is ... Supported by some advocacy groups, a number of class-action lawsuits were filed against GlaxoSmithKline, alleging the vaccine ... Ixodes larvae and nymphs typically wait for potential hosts ("quest") on leaves or grasses close to the ground with forelegs ...
The action potential in a normal skeletal muscle cell is similar to the action potential in neurons. Action potentials result ... of Arizona A cartoon illustrating the action potential Action potential propagation Production of the action potential: voltage ... The cardiac action potential differs from the neuronal action potential by having an extended plateau, in which the membrane is ... Action potentials in neurons are also known as "nerve impulses" or "spikes", and the temporal sequence of action potentials ...
... the atrial action potential are action potentials that occur in the heart atrium. They are similar to ventricular action ... Cardiac action potential Vigmond E.J, Tsoi V, Yin Y, Page P, & Vinet A. (2009). Estimating Atrial Action Potential Duration ... Also, in comparison to the ventricular action potential, atrial action potentials have a more gradual repolarization period. ... Vigmond E.J, Tsoi V, Yin Y, Page P, & Vinet A. (2009). Estimating Atrial Action Potential Duration from Electrograms. IEEE ...
Role of sodium channel subtype in action potential generation by neocortical pyramidal neurons Efrat Katz, Ohad Stoler, Anja ... Optical magnetic detection of single-neuron action potentials using quantum defects in diamond John F. Barry, Matthew J. Turner ... Covariation of axon initial segment location and dendritic tree normalizes the somatic action potential Mustafa S. Hamada, ...
The compound muscle action potential (CMAP) or compound motor action potential is an electromyography investigation (electrical ... 2009). "Prolonged compound muscle action potential duration in critical illness myopathy". Muscle Nerve. 40 (6): 1040-2. doi: ... have prolonged compound muscle action potential.[1]. References[edit]. *^ Goodman BP; et al. ( ... The CMAP idealizes the summation of a group of almost simultaneous action potentials from several muscle fibers in the same ...
The Division is reminding system participants that enforcement actions may be taken against stakeholders who perform any ... Texas: Potential Enforcement Action. The Division is reminding system participants that enforcement actions may be taken ... Further, the Division suggests that a PBMs use of proprietary formularies for legacy claims could trigger enforcement action. ... The Division is warning carriers they may initiate enforcement action if the EDI-03 is not completed. ...
The beginning sounds like something Id be humming to myself and never quite satisfied with, but made actually good. That not-quite-pointless multiple notes rather than one longer note ...
Neuronal action potential[edit]. This animated gif illustrates action potential propagation in an axon. Three types of ion ... Cardiac action potential[edit]. Estimations of the number of ions involved in generating the upstroke of the action potential[ ... The voltage across the capacitor is the membrane potential (see action potential for an example of a membrane RC circuit). ... approaching the sodium equilibrium potential. The positive-inside voltage during the action potential in the initial segment ...
Action Potential is a forum operated by neuroscience editors at Nature for the entire neuroscience community. Well discuss ... This is a great article; I am pleased to see Action Potential and, importantly, Nature tackling the issue of gender…. ... Read ...
Synaptically triggered action potentials in dendrites.. Regehr W1, Kehoe JS, Ascher P, Armstrong C. ... We tested the hypothesis that action potentials originate in apical dendrites of pyramidal cells. Layer V somata were voltage ... We conclude that Na+ action potentials are initiated in the apical dendrite in response to synaptic input. ...
In the neuron an action potential produces the nerve impulse, and in the muscle cell it produces the contraction required for ... Action potential, the brief (about one-thousandth of a second) reversal of electric polarization of the membrane of a nerve ... When depolarization reaches the threshold potential, it triggers an action potential. Generation of the action potential brings ... More About Action potential. 9 references found in Britannica articles. Assorted References. *definition* In resting potential ...
To calculate: The rate at which the action potentials are produces by the nerve if the number of action potentials produced by ... The number of action potentials produced by a nerve, t seconds after a stimulus, is given by the equation N. (. t. ). =. 25. t ... Nerve response The number of action potentials produced by a nerve, t seconds after a stimulus, is given by ... Find the rate at which the action potentials are produced by the nerve. ...
The intention of this investigation was to acquire more concise information about the nature of the action potential of Dionaea ... firing action potentials with pronounced after-hyperpolarizations. The action potentials are strictly dependent on Ca2+. Their ... Action potential Dionaea Plasma membrane (freeze etching) Resting potential Sensory cell Abbreviations. DNP. 2,4-dinitrophenol ... Gaffey, C.T., Mullins, L.J. (1958) Ion fluxes during the action potential in Chara. J. Physiol. 144, 505-524Google Scholar ...
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... a momentary reversal in electrical potential across a plasma membrane (as of a neuron or muscle fiber) that occurs when a cell ... Dictionary Entries near action potential. action noun action-packed action painting action potential action replay action- ... Share action potential Post the Definition of action potential to Facebook Share the Definition of action potential on Twitter ... Encyclopedia article about action potential. Comments on action potential What made you want to look up action potential? ...
... James Peterson and Taufiquar Khan ... We use generated families of action potentials from a classic Hodgkin-Huxley model to verify our methodology and build toxin ... We focus on event detection in action potential via abstraction of information content into a low dimensional feature vector ... present a robust methodology using mathematical pattern recognition schemes to detect and classify events in action potentials ...
If you know the author of The Ionic Basis for the Action Potential, please help us out by filling out the form below and ... The Ionic Basis for the Action Potential "In the following discussion, we look carefully at how each ion contributes to changes ... in membrane potential during an "action potential" by following what happens to sodium, potassium, and chloride conductances." ... Disciplines with similar materials as The Ionic Basis for the Action Potential. ...
The action potential in a normal skeletal muscle cell is similar to the action potential in neurons.[56] Action potentials ... Thus, the cell fires, producing an action potential.[4][7][8][note 1] The frequency at which a neuron elicits action potentials ... Action potential propagation. *Production of the action potential: voltage and current clamping simulations[permanent dead link ... Cardiac action potentialsEdit. Main articles: Cardiac action potential, Electrical conduction system of the heart, Cardiac ...
CUPE Local 7000, which represents SkyTrain workers at the BC Rapid Transit Company, has announced potential full strike action ... Q: What if Im an SFU staff member impacted by the strike action and have no alternative ways to get to campus?. If you have ... Q: How will I know if there is strike action or if travel to campus is interrupted?. If you rely on transit, please check ... Q: What if Im an SFU student impacted by the strike action and have no alternative ways to get to campus?. Contact your ...
action potential synonyms, action potential pronunciation, action potential translation, English dictionary definition of ... action potential. n. A momentary change in electrical potential on the surface of a cell, especially of a nerve or muscle cell ... Related to action potential: membrane potential, Cardiac action potential. action potential. n.. A momentary change in ... Action potential - definition of action potential by The Free Dictionary https://www.thefreedictionary.com/action+potential ...
The Board of Environmental Protection has suspended proceedings until potential conflicts of interest for some members are ... Until the issue is resolved, BEP Chairwoman Susan Lessard has suspended official actions by the board, said Cynthia Bertocci, ... Since then, "more than one" board member was believed to have potential conflicts of interest, LePage spokeswoman Adrienne ... AUGUSTA - The Board of Environmental Protection has suspended proceedings until potential conflicts of interest for some ...
Potential PFOA Precursors. Source: Report # M-231/2014 , September 19th, 2014 , By Claus Jorgen Nielsen, University of Oslo ... The present report summarises a classification of potential PFOA precursors and outlines the transformation routes leading to ... on the potential of abiotic degradation resulting in PFOA. ...
I find myself needing a mathematical rule for determining the end ,, of a motor unit action potential. For example, I could ... motor unit action potential duration (repost). Venkatesh Murthy venk at stein.u.washington.edu Tue Jan 12 23:27:44 EST 1993 * ... If you want to get more detailed, you can fit a regression line to the last consistent turn in your action potential and ... Im assuming you need this so that you can isolate different action potential shapes from the same electrode. Let me know if ...
The generation and propagation of the action potential require sodium influx via voltage‐dependent sodium channels that drive ... Action potential threshold is determined by the relative activity of sodium vs. potassium channels with an action potential ... Figure 1. The action potential. (a) An action potential recorded from a rat sympathetic neuron during a 400‐ms current ... Figure 5. Computer simulation of the action potential using the Hodgkin-Huxley model. (a) Shows the simulated action potential ...
Single-neuron action potential magnetic sensing. John F. Barry, Matthew J. Turner, Jennifer M. Schloss, David R. Glenn, Yuyu ... Single-neuron action potential magnetic sensing. John F. Barry, Matthew J. Turner, Jennifer M. Schloss, David R. Glenn, Yuyu ... 1974) Changes of action potential shape and velocity for changing core conductor geometry. Biophys J 14(10):731-757. ... 1980) A calculation of the magnetic field of a nerve action potential. Biophys J 32(2):719-731. ...
Characteristics of Action Potentials[edit]. There are a few components to the action potential. On a graph, plotting membrane ... the current of Na and the total current during one action potential; the graph lines up action potential curve with graph of ... Action Potential Current[edit]. A current clamp can be used to monitor current. The injection electrode will trigger an action ... Influx of Na causes rising part of action potential and the efflux of K brings the membrane potential back down ...
Simulator for neural networks and action potentials: description and application.. Ziv I1, Baxter DA, Byrne JH. ... 1. We describe a simulator for neural networks and action potentials (SNNAP) that can simulate up to 30 neurons, each with up ... Simulated cells included those that respond to depolarization with tonic firing, adaptive firing, or plateau potentials as well ...
... to help deaf pupils reach potential on ITV News, videos, stories and all the latest Wales news ... The Welsh Government says it is committed to ensuring all children reach their potential. ...
Randy Baumgardner faces potential punishment for allegedly slapped and grabbed the buttocks of a legislative aide according to ... Colorado lawmaker faces potential disciplinary action after sexual harassment complaint deemed credible A former legislative ... The protocol puts disciplinary action in the hands of the leadership of the respective body but does not outline potential ... A top Republican lawmaker in Colorado is facing potential disciplinary action for sexual harassment after an outside ...
... The worlds top smartphone maker last week permanently ended sales of ... Ltd.s U.S. unit is facing a proposed class action lawsuit from three Galaxy Note 7 customers, according to a filing in a ...
Humorous views on interesting, bizarre and amusing articles, submitted by a community of millions of news junkies, with regular Photoshop contests.
  • Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, endocrine cells and in some plant cells. (wikipedia.org)
  • Quanta Magazine , "Hidden Computational Power Found in the Arms of Neurons," 14 Jan. 2020 Neurons firing action potentials that affect the downstream cells they are wired to (via synapses) are one type of mechanism, as are electronic circuits, made of transistors, capacitances, resistances and wires. (merriam-webster.com)
  • neurons are constantly sending each other information in the form of electrical pulses, known as spikes or action potentials . (merriam-webster.com)
  • This is the basis of an action potential in excitable cells such as neurons. (thefreedictionary.com)
  • a) A subthreshold current injection does not induce the neurons to discharge an action potential. (els.net)
  • b) A larger current injection depolarises the neurons beyond threshold to discharge a single action potential. (els.net)
  • In regular firing neurons, the cell continues to generate action potentials as long as the membrane potential stays above threshold. (wikibooks.org)
  • 1. We describe a simulator for neural networks and action potentials (SNNAP) that can simulate up to 30 neurons, each with up to 30 voltage-dependent conductances, 30 electrical synapses, and 30 multicomponent chemical synapses. (nih.gov)
  • So many neurons would have a resting membrane potential of around negative 60 millivolts and a threshold potential of around negative 50 millivolts or so that I've drawn with a dashed line. (khanacademy.org)
  • The voltage-gated Na and K channels in neurons are responsible for action potential generation. (mit.edu)
  • Neurons in the cortex communicate with each other by sending electrical discharges, called action potentials or spikes. (siam.org)
  • Action potential is an event that happens between neurons in order to send messages from the brain to the different parts of the body, whether for voluntary or involuntary actions. (wisegeek.com)
  • Here, we investigate electrical signaling in dendritic spines using voltage-sensitive dye imaging in cortical pyramidal neurons during backpropagating action potentials and synaptic input. (jneurosci.org)
  • Examples of cells that signal via action potentials are neurons and muscle cells. (moleculardevices.com)
  • The tutorial will begin with an explanation of how the Resting Potential of -70mV (across the axonal membrane) is generated based on the ions present, passive transport membranes present and the biophysical structure and size of the neurons - with emphasis on the axon. (sophia.org)
  • Neurons transform time-varying inputs into action potentials emitted stochastically at a time dependent rate. (duke.edu)
  • The movement of positively-charged sodium and potassium ions through these ion channels controls the membrane potential of the axon. (wikiversity.org)
  • Sodium ions entering through the sodium channels shift the membrane potential to positive-inside, approaching the sodium equilibrium potential. (wikiversity.org)
  • Potassium ions leaving the axon through voltage-gated potassium channels return the membrane potential to negative-inside values near the potassium equilibrium potential. (wikiversity.org)
  • When the voltage-gated potassium channels gate shut, the membrane potential returns to the resting potential. (wikiversity.org)
  • This is because the membrane potential occurs only right next to the membrane . (wikiversity.org)
  • The membrane potential is stored in the membrane capacitance , which physically is only the charges in direct contact with the membrane surfaces. (wikiversity.org)
  • The voltage across the capacitor is the membrane potential (see action potential for an example of a membrane RC circuit). (wikiversity.org)
  • Knowing that, one needs only to calculate how much current needs to flow to discharge the membrane capacitance to calculate the number of charges that must flow across the membrane to change the capacitor voltage (membrane potential) by, say 100 mV. (wikiversity.org)
  • In physiology, an action potential (AP) occurs when the membrane potential of a specific cell location rapidly rises and falls: this depolarization then causes adjacent locations to similarly depolarize. (wikipedia.org)
  • These channels are shut when the membrane potential is near the (negative) resting potential of the cell, but they rapidly begin to open if the membrane potential increases to a precisely defined threshold voltage, depolarising the transmembrane potential. (wikipedia.org)
  • When the channels open, they allow an inward flow of sodium ions, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential towards zero. (wikipedia.org)
  • The process proceeds explosively until all of the available ion channels are open, resulting in a large upswing in the membrane potential. (wikipedia.org)
  • citation needed] Nearly all cell membranes in animals, plants and fungi maintain a voltage difference between the exterior and interior of the cell, called the membrane potential. (wikipedia.org)
  • In most types of cells, the membrane potential usually stays fairly constant. (wikipedia.org)
  • At the resting potential, the membrane potential is close to E K , the equilibrium potential of K + . When sodium channels open, the membrane depolarizes. (britannica.com)
  • In the following discussion, we look carefully at how each ion contributes to changes in membrane potential during an "action potential" by following what happens to sodium, potassium, and chloride conductances. (merlot.org)
  • The membrane potential remains near a baseline level until at some point in time, it abruptly spikes upward and then rapidly falls. (wikipedia.org)
  • On a graph, plotting membrane potential vs. time, the slope become steep and the potential goes over 0 mV in the overshoot phase. (wikibooks.org)
  • Charge may be injected via the electrode, which causes a depolarization that, when the membrane potential reaches the threshold, causes a spike. (wikibooks.org)
  • Uses two electrodes: one to inject voltage and one to monitor membrane potential. (wikibooks.org)
  • Here's our graph of the membrane potential on the y-axis and time on the x-axis. (khanacademy.org)
  • The membrane of an axon as many voltage gated ion channels, most of which open when the membrane potential crosses a threshold value. (khanacademy.org)
  • This is going to cause the membrane potential, which has already gone from the resting potential to the threshold potential from the grated potentials, but now that all this sodium is flowing in through these open channels, the membrane potential is going to dramatically rise trying to head toward the equilibrium potential of sodium, which is usually somewhere around positive 50 millivolts. (khanacademy.org)
  • This rapid increase in the membrane potential values is due to these voltage gated sodium channels. (khanacademy.org)
  • And after they close, they're in a special state called the inactivated state and they're unable to open at any membrane potential for a brief time. (khanacademy.org)
  • The next thing we see happen to the action potential, basically just as fast as the membrane potential went from the resting potential to the peak of the action potential, it then rapidly descends back toward the resting potential and then actually goes farther. (khanacademy.org)
  • At rest, the ventricular myocyte membrane potential is about -90 mV, which is close to the potassium reversal potential . (bionity.com)
  • When an action potential is generated, the membrane potential rises above this level in four distinct phases. (bionity.com)
  • This causes the membrane potential to rise at a rate of about 300 V/s. (bionity.com)
  • This outward potassium current causes a small dip in membrane potential shortly after depolarization . (bionity.com)
  • We performed action potential imaging on isolated adult cardiomyocytes of guinea pigs utilizing the fluorescent membrane potential sensor di-8-ANEPPS and latest electron-multiplication CCD as well as scientific CMOS cameras of several manufacturers. (spie.org)
  • the change in membrane potential occurring in nerve, muscle, or other excitable tissue when excitation occurs. (thefreedictionary.com)
  • An all-or-none electrical event (neural impulse) in an axon or muscle fibre in which the polarity of the membrane potential is rapidly reversed and re-established. (thefreedictionary.com)
  • the remaining 4 phases (1 through 4) are concerned with returning the cell to its resting membrane potential, where it remains until the next stimulus. (thefreedictionary.com)
  • During hyperpolarization of the membrane potential, the amplitude of the synaptic voltage in spines was increased, consistent with the expected change resulting from the increased driving force. (jneurosci.org)
  • Prior to an action potential, the neuron is at rest, with a membrane potential of -70 mV. (blausen.com)
  • The sodium ions that rush across the cell membrane change the trans-membrane potential rapidly from threshold toward zero mV. (blausen.com)
  • An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane with a characteristic pattern. (moleculardevices.com)
  • Depolarization is caused by a rapid rise in membrane potential opening of sodium channels in the cellular membrane, resulting in a large influx of sodium ions. (moleculardevices.com)
  • Hyperpolarization is a lowered membrane potential caused by the efflux of potassium ions and closing of the potassium channels. (moleculardevices.com)
  • Resting state is when membrane potential returns to the resting voltage that occurred before the stimulus occurred. (moleculardevices.com)
  • Now in order for another action potential to occur, you have to restore the resting membrane potential which is done so by sodium/potassium pumps . (sophia.org)
  • A protein that pumps sodium potassium against their concentration gradients to restore the resting membrane potential following an action potential. (sophia.org)
  • When depolarization reaches the threshold potential, it triggers an action potential. (britannica.com)
  • Na + channels open at the beginning of the action potential, and Na + moves into the axon, causing depolarization . (wikipedia.org)
  • Also, if the depolarization is increased to a more positive potential, these cells fire at a faster rate. (wikibooks.org)
  • When enough Na channels let in enough Na that the efflux of K can't balance the depolarization, the depolarization continues and action potential occurs. (wikibooks.org)
  • Simulated cells included those that respond to depolarization with tonic firing, adaptive firing, or plateau potentials as well as endogenous pacemaker and bursting cells. (nih.gov)
  • A recording from a single point will show the various stages of the action potential enacted--depolarization, repolarization, hyperpolarization--as the wave passes. (fact-index.com)
  • In the human body the dynamic of depolarization-resting potential-repolarization occurs at several scales as well for the heart is far larger than a cell. (thunderbolts.info)
  • The action potential is triggered when the stimulus causes a depolarization. (omninoggin.com)
  • Cardiology The constellation of changes in electric potential generated by myocardial cell membranes after stimulation Physiology The sequential, electrochemical polarization and depolarization that traverses the membrane of a neuron in response to mechanical stimulation-eg, touch, pain, cold, etc. (thefreedictionary.com)
  • Parallel to the discovery and use of surface multiphasic potentials, research on injury potentials for the study of the complete depolarization-repolarization (monophasic) cycle of the cardiac cell continued. (scielo.br)
  • Magnetic fields from neuronal action potentials (APs) pass largely unperturbed through biological tissue, allowing magnetic measurements of AP dynamics to be performed extracellularly or even outside intact organisms. (pnas.org)
  • Despite their potential importance in neuronal function, direct experimental evidence on electrical signaling in dendritic spines is lacking as their small size makes them inaccessible to standard electrophysiological techniques. (jneurosci.org)
  • Also, in comparison to the ventricular action potential, atrial action potentials have a more gradual repolarization period. (wikipedia.org)
  • Repolarization is accomplished by channels that open slowly and are mostly activated at the end of the action potential (slow delayed-rectifier channels), and channels that open quickly but are inactivated until the end of the action potential (rapid delayed rectifier channels). (bionity.com)
  • Pharmacological investigations suggested that axonal action potential repolarization in both cell types depends critically upon Kv1 channels, whereas the axonal and somatic action potentials of somatostatin-expressing interneurons also depend on BK Ca 2+ -activated K + channels. (jneurosci.org)
  • Samsung Electronics Co. Ltd.'s U.S. unit is facing a proposed class action lawsuit from three Galaxy Note 7 customers, according to a filing in a federal court in Newark, N.J. (entrepreneur.com)
  • Israeli plaintiffs are seeking to file a class action lawsuit against Apple, ARM, and Intel over the Meltdown and Spectre vulnerabilities recently uncovered in Intel and ARM-based processors. (appleinsider.com)
  • Michael Bloomberg's presidential campaign is facing a potential class action lawsuit for allegedly promising jobs through November to more than a thousand campaign staffers and then laying them off last week. (nbcdfw.com)
  • But the bill is no shock to attorney Ari Brown of the Terrell Marshall Law Group, who last week filed a proposed class-action lawsuit against Seattle City Light, seeking unspecified damages over the use of what it calls "wildly incorrect" estimates to bill customers. (seattletimes.com)
  • DENVER -- The first class-action lawsuit has been filed against Equifax in Colorado by Hannon Law over the company's huge security breach. (kdvr.com)
  • Watts works in finance with a criminal justice background and is one of thousands of Colorado consumers joining the class-action lawsuit. (kdvr.com)
  • Fortnite continues to be catnip for lawyers, this time finding itself targeted by a Montreal legal firm that's requested authorisation for a class action lawsuit on behalf of parents of two children who are allegedly addicted to the battle royale. (pcgamer.com)
  • It believes the case has the same legal basis as a 2015 class action lawsuit against tobacco companies for not informing customers about the danger to their health. (pcgamer.com)
  • While Fortnite includes a waiver to stop people from being part of a class action lawsuit, Calex Légal claims that, in Quebec, it would be negated by the Consumer Protection Act, which requires companies to warn customers about potential risks, like addiction. (pcgamer.com)
  • c) A suprathreshold current injection sufficiently depolarises the neuron that multiple action potentials are generated during the 400‐ms injection. (els.net)
  • A range of kits are available for appropriate types of surface action potentials including monophasic, biphasic, and even multiple action potentials. (adinstruments.com)
  • We demonstrate noninvasive detection of action potentials with single-neuron sensitivity, including in whole organisms. (pnas.org)
  • The effect of increasing stimulus strength on action potential generation. (els.net)
  • No. The action potential once started needs to be completed before it can accept another stimulus to cause another action potential. (omninoggin.com)
  • Stimulus starts the rapid change in voltage or action potential. (moleculardevices.com)
  • An action potential occurs when a stimulus causes the voltage difference across a cell membrane to shift. (sophia.org)
  • Action potentials in cardiac myocytes have durations in the order of magnitude of 100 milliseconds. (spie.org)
  • Action potential imaging based on isolated adult cardiomyocytes can be utilized in pharmacological cardiac safety screens bearing numerous advantages over approaches based on heterologous expression of hERG channels in cell lines. (spie.org)
  • Isolated heart kits that allow surface cardiac action potential ("ECG") measurements from an isolated perfused rodent heart in Langendorff and Working Heart systems. (adinstruments.com)
  • Since the 18th century, when Galvani introduced the concept of 'animal electricity', electric potentials have been observed and recorded in different nerves and muscles, including hearts and isolated preparations of cardiac tissue. (scielo.br)
  • In 1883, Burdon-Sanderson and Page 2 obtained continuous recordings of the potentials generated by frog cardiac beats. (scielo.br)
  • With the ability to measure the cardiac potentials on the surface of the body, electrophysiology was no longer practiced only in the laboratories, but began to have significant clinical applications. (scielo.br)
  • The significant theoretical findings provided by the cellular impalement method caused research on cardiac cellular potentials to focus on transmembrane measurements, thus interest in the old technique of the monophasic injury potential diminished. (scielo.br)
  • This restores the original ion concentrations and readies the cell for a new action potential. (britannica.com)
  • Changes in external ion concentrations affect resting and action potentials in both cell types in a similar way. (springer.com)
  • Furthermore, we characterized the signal to noise ratio of action potential signals of varying sets of cameras, dye concentrations and objective lenses. (spie.org)
  • We ensured that di-8-ANEPPS itself did not alter action potentials by avoiding concentrations above 5 μM. (spie.org)
  • In the generation of the action potential, stimulation of the cell by neurotransmitters or by sensory receptor cells partially opens channel-shaped protein molecules in the membrane. (britannica.com)
  • Methods of using unidirectionally propagating action potentials (UPAPs) for cavernous nerve stimulation and for certain disorders are provided. (google.es)
  • applying the stimulation to the cavernous nerve to effectively select orthodromic action potentials traveling in one direction along the nerve, thereby limiting side effects of bidirectional stimulation. (google.es)
  • Because ion channels open and close in a stochastic fashion, spontaneous (ectopic) action potentials can result even in the absence of stimulation. (mit.edu)
  • It is shown by microelectrode measurements that, besides the sensory cells, all the major tissues of the trap lobes are excitable, firing action potentials with pronounced after-hyperpolarizations. (springer.com)
  • The resting potentials of sensory cells (-161±7 mV) and mesophyll cells (-155±8 mV) are of the same magnitude. (springer.com)
  • 8%) (prolonged sensory response latency, slower sensory conduction velocity, non-obtained sensory nerve action potential , etc. (thefreedictionary.com)
  • Venki Murthy ( venk at u.washington.edu ) PS: You may also wish to consult the literature on template matching for action potential recognition - usually applied to neural recordings. (bio.net)
  • Simulator for neural networks and action potentials: description and application. (nih.gov)
  • The recovery of sodium channels from inactivation and the closing of potassium channels following the action potential determine the refractory period, which is a period of increased action potential threshold. (els.net)
  • Once an initiation in an action potential occurs, a refractory period is observed. (omninoggin.com)
  • 1. Absolute refractory period means there is absolutely no stimuli, no matter how strong, will cause another action potential. (omninoggin.com)
  • 2. Relative refractory period means the duration of an action potential that may be able to be depolarized again because of another stimuli. (omninoggin.com)
  • The generation and propagation of the action potential require sodium influx via voltage‐dependent sodium channels that drive the upstroke of the action potential. (els.net)
  • I'm assuming you need this so that you can isolate different action potential shapes from the same electrode. (bio.net)
  • If a recording electrode is placed close to the cell, it allows recording the action potentials across the membrane. (wikibooks.org)
  • The injection electrode will trigger an action potential by injecting a suprathreshold voltage, but the potential across the membrane is held steady. (wikibooks.org)
  • The probable explanation for the existence of this potential is that injury destroys the selective permeability of the cellular membrane, reducing the membrane's electrical resistance, allowing that an electrode placed in the injured region contacts the cellular cytoplasm through a fluid pathway of relatively low resistance 1 . (scielo.br)
  • In one of their observations, when an electrode was placed on the intact surface of the heart and another on an injured region, transitory monophasic potential (only one polarity) was recorded in opposition to the known transitory multiphase recordings (positive and negative polarities). (scielo.br)
  • In 1966, Korsgren et al 9 used the works of Schutz 10 (1931) to introduce a suction electrode that captured monophasic potentials with great simplicity, not requiring the production of a specific myocardial lesion, because this was already caused by the suction itself. (scielo.br)
  • When an external event causes the membrane electrical potential to increase and depolarize, the voltage-gated ion channels open and cause an influx of sodium ions into the axon. (reference.com)
  • if the current is insufficient to depolarize the membrane to the threshold level, an action potential will not fire. (moleculardevices.com)
  • They are similar to ventricular action potential with the exception of having a more narrow phase 2 (plateau phase) due to a smaller calcium influx. (wikipedia.org)
  • Effect of STV on Action Potential of Guinea Pig Ventricular Myocytes. (thefreedictionary.com)
  • It uses material from the Wikipedia article "Ventricular_action_potential" . (bionity.com)
  • If this local potential reaches a critical state called the threshold potential (measuring about −60 mV), then sodium channels open completely. (britannica.com)
  • In response to a signal from another neuron , sodium- (Na + ) and potassium- (K + ) gated ion channels open and close as the membrane reaches its threshold potential . (wikipedia.org)
  • This threshold potential varies but generally is about 15 millivolts above the resting potential of the cell. (fact-index.com)
  • So we've talked about the threshold potential before. (khanacademy.org)
  • And the importance of this threshold potential is that it determines if these voltage gated ion channels will open. (khanacademy.org)
  • And when the threshold potential is crossed, it's going to open. (khanacademy.org)
  • Magnesium ions only slightly affect the peak depolarizations but considerably prolong action potentials. (springer.com)
  • Action potentials are depolarizations that start at the initial segment of an axon and are propagated toward the synaptic terminals. (blausen.com)
  • the change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated, serving to transmit nerve signals. (thefreedictionary.com)
  • Jitter measurement with a CNE have risks, such as the triggering and/or jittering potentials being compound signals due to summation, and showing extra phases rather than a clear single-fiber action potential (18). (thefreedictionary.com)
  • As the traveling signals of nerves and as the localized changes that contract muscle cells, action potentials are an essential feature of animal life. (fact-index.com)
  • The action potentials are strictly dependent on Ca 2+ . (springer.com)
  • Sodium influx via voltage‐dependent sodium channels depolarises the membrane to activate more sodium channels in a positive feedback mechanism that generates the ballistic rising phase of the action potential. (els.net)
  • The reduction of sodium influx resulting from inactivation combined with potassium efflux from the cell via voltage‐dependent and/or voltage‐independent potassium channels drive the repolarisation phase of the action potential. (els.net)
  • The voltage‐dependent potassium channels often remain active following the action potential (slow to close) to generate an afterhyperpolarization (AHP). (els.net)
  • This is reasoned by the fact that the action potential initiation is dependent on the sodium channel opening. (omninoggin.com)
  • A momentary change in electrical potential on the surface of a cell, especially of a nerve or muscle cell, that occurs when it is stimulated, resulting in the transmission of an electrical impulse. (thefreedictionary.com)
  • In this final recovery stage, the neuron returns to its normal state of -7 mV, until another episode of action potential occurs. (wisegeek.com)
  • The beginning of the action potential, phase 1, specialized membrane proteins ( voltage-gated sodium channels ) in the cell membrane selectively allow sodium ions to enter the cell. (bionity.com)
  • In order for this action potential to occur, the voltage difference across a cell membrane has to shift by a certain amount. (sophia.org)
  • The negative-inside resting potential is mostly determined by potassium ions leaving the cell through leak channels. (wikiversity.org)
  • A question concerning a number of ions traversing the membrane during action potential and whether or not they can significantly alter the ionic gradients is addressed in this section. (wikiversity.org)
  • The declining phase of the action potential is caused by the closing of sodium channels and the opening of potassium channels, which allows a charge approximately equal to that brought into the cell to leave in the form of potassium ions. (britannica.com)
  • Recent Examples on the Web This was noteworthy because conventional action potentials are usually caused by sodium and potassium ions. (merriam-webster.com)
  • When the brain "sends" a message, a significant amount of +Na ions enter the neuron, and the rising and overshoot stages of action potential occur. (wisegeek.com)
  • To let out positive ions, the potassium channels will open as soon as the sodium channels close, and the falling and undershoot stages of action potential take place. (wisegeek.com)
  • This excitation was hitherto held to rely only on an electric phenomenon, the action potential, triggered by transient modifications in the concentration of ions from each side of the membrane. (scitizen.com)
  • We tested the hypothesis that action potentials originate in apical dendrites of pyramidal cells. (nih.gov)
  • For recording a single monophasic action potential from an isolated mouse heart using a spring loaded platinum tipped lead to maintain constant contact with the beating heart without destroying or damaging tissue. (adinstruments.com)
  • Monophasic action potential. (scielo.br)
  • This was the origin of the term monophasic action potential (MAP), whose form was very similar to the cellular action potential later obtained by the cellular impalement technique with microelectrodes (IT). (scielo.br)
  • We focus on event detection in action potential via abstraction of information content into a low dimensional feature vector within the constrained computational environment of a biosensor. (hindawi.com)
  • At the beginning of the nineties, using neuropharmacological techniques, we made a surprising discovery: the afferent and efferent messages organizing this gastroduodenal inhibitory (GIR) reflex along the nervous fibres are independent of action potentials (Mazet et al, 1993). (scitizen.com)
  • Sometimes called a propagated potential because a wave of excitation is actively transmitted along the nerve or muscle fibre, an action potential is conducted at speeds that range from 1 to 100 metres (3 to 300 feet) per second, depending on the properties of the fibre and its environment . (britannica.com)
  • We then established that raft integrity was necessary to the conduction of excitation without action potentials. (scitizen.com)
  • Action potentials are initiated in the axon initial segment after neurotransmitter activates excitatory receptors in the neuron's dendrites and cell body. (wikiversity.org)
  • The action potentials generated in the somata and axons, including axon collaterals, of somatostatin-expressing interneurons are significantly broader than those generated in the same compartments of fast-spiking inhibitory interneurons. (jneurosci.org)
  • In electrocardiography, the atrial action potential are action potentials that occur in the heart atrium. (wikipedia.org)
  • Estimating Atrial Action Potential Duration from Electrograms. (wikipedia.org)
  • In many cases, when the brain needs to "send" many "messages," action potential can occur in a series called a "spike train. (wisegeek.com)
  • It is very interesting to know that all these stages of action potential occur in as short as two milliseconds. (wisegeek.com)
  • So potassium and sodium are very important in setting the stage for an action potential and the threshold is the minimum shift needed for an action potential to occur. (sophia.org)
  • they're the steps that occur in an action potential. (sophia.org)
  • When positive-inside membrane potentials are reached, voltage-gated potassium channels open and voltage-gate sodium channels close. (wikiversity.org)
  • Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane. (wikipedia.org)
  • Changes in ion permeance underlying the action potentialElectrical potential is graded at left in millivolts, ion permeance at right in open channels per square millimetre. (britannica.com)
  • In the Hodgkin-Huxley membrane capacitance model , the speed of transmission of an action potential was undefined and it was assumed that adjacent areas became depolarised due to released ion interference with neighbouring channels. (wikipedia.org)
  • The action potential diffuses through the membrane by T tubules Ca 2+ channels and activates the RE. (thefreedictionary.com)
  • The AHP can speed sodium channel recovery from inactivation, which is faster at more hyperpolarised voltages, so that the channels are more rapidly reset to participate in generating the next action potential. (els.net)
  • Action potential threshold is determined by the relative activity of sodium vs. potassium channels with an action potential being generated if the sodium influx is larger than the potassium efflux. (els.net)
  • High‐density clustering of sodium channels at the nodes of Ranvier ensures sufficient current is generated to exceed threshold at the next node so that the action potential is faithfully propagated along the axon. (els.net)
  • Using TEA(tetraethylammonium, an antagonist for K channels) they suppressed the outward component of the action potential, and they could look at the current vs. time graph of an action potential and extrapolate the current v. time graphs for K and Na individually. (wikibooks.org)
  • When suprathreshold potential is applied, Na channels open and then close even though membrane is depolarized. (wikibooks.org)
  • The rapid, large change in potential is the result of the activities of ion channels. (wikibooks.org)
  • The first in this lighter grey are the leak channels that we talked about when we talked about the neuron resting potential. (khanacademy.org)
  • But to talk about the action potential, I need to introduce an entirely new type of channel that I've drawn in dark grey with this little v. And these are voltage gated ion channels. (khanacademy.org)
  • The trigger zone has the greatest density of these voltage gated sodium channels which is why action potentials usually starts at the trigger zone. (khanacademy.org)
  • And the reason for that is that these voltage gated sodium channels automatically start to close at the higher potential values so that sodium stops flowing into the neuron. (khanacademy.org)
  • As sodium channels close calcium provides current to maintain the potential around 10 mV. (bionity.com)
  • Fast delayed rectifier channels open quickly but are shut by inactivation at high membrane potentials. (bionity.com)
  • The action potential is generated in voltage-gated ion channels that are present in the plasma membrane of a cell. (reference.com)
  • These ion channels are activated by changes in the electrical potential of the membrane near the channel. (reference.com)
  • Conduction failure was common at branch points and regularly spaced boutons en passant. (nih.gov)
  • The Action Potential propagation involves a passive event called: Passive Spread or Electrotonic conduction. (physicsforums.com)
  • Thus, the kinetics of sodium and potassium channel gating determine not only the action potential shape and duration but also the threshold for action potential generation. (els.net)
  • So when there is enough temporal and spatial summation of excitatory grad potentials to get us toward the threshold, here at the trigger zone, at the initial segment of the axon, so let me just draw that, that we have temporal and spatial summation of excitatory potentials spreading across the membrane of the soma into the initial segment of the axon, the trigger zone. (khanacademy.org)
  • Action Potential is a forum operated by neuroscience editors at Nature for the entire neuroscience community. (nature.com)
  • In addition to these many putative mechanisms, it has also been proposed that the neuroprotective effects of lithium are key to its therapeutic actions. (springer.com)
  • Our sensor is composed of quantum defects within a diamond chip, which detect time-varying magnetic fields generated by action potentials. (pnas.org)
  • Optical magnetic detection with quantum defects also provides information about action potential propagation that is not easily available with existing methods. (pnas.org)
  • 9 . The method of claim 8 wherein the at least one sensed physical condition includes at least one of penile tumescence, penile arteriole pressure, nitric oxide concentration, and action potentials propagating along the cavernous nerve. (google.es)
  • Since the Ca 2+ influx during a single action potential does not suffice to reach this threshold, at least two stimulations of the trap are necessary to elicit movement. (springer.com)
  • The reduced sodium influx along with increased potassium efflux permits rapid action potential repolarisation. (els.net)
  • Note: The influx of sodium into the cell will bring the potential in the cell to about 35-40mV (see picture). (omninoggin.com)
  • The resulting resting potential usually measures about −75 millivolts (mV), or −0.075 volt , the minus sign indicating a negative charge inside. (britannica.com)
  • If the entry of sodium into the fibre were not balanced by the exit of another ion of positive charge, an action potential could not decline from its peak value and return to the resting potential. (britannica.com)
  • After it comes back down, the potential undershoots, and the resting potential returns. (wikibooks.org)
  • And in fact, it becomes more positive inside the neuron membrane during this period that it's the reverse of the resting potential because normally it's more negative inside than outside the neuron membrane. (khanacademy.org)
  • Often times, the potassium will efflux enough to cause a hyperpolarization (meaning that the inside of the cell is more negative than what it's resting potential was). (omninoggin.com)
  • Also, the neuron or cell needs to, at least be at its resting potential or in hyperpolarization in order for it to go about its second stimuli. (omninoggin.com)
  • In the absence of an impulse, the inside is electrically negative and the outside is positive (the resting potential). (thefreedictionary.com)
  • Using the injury potential method, researchers found that certain cells, classified as excitable, suffered sudden and transitory alterations in resting potential, with later return to the initial value ( Fig. 1-B ). This cycle was named cellular action potential. (scielo.br)
  • In a previous study, we found that Primo vessels generate different action potentials in smooth muscles, but this study compared the pulse shape to distinguish the two tissues. (hindawi.com)
  • In an unmyelinated axon that is "firing" an action potential, the transmembrane potential at any instant will vary from point to point along the fiber, with its amplitude depending on whether the A.P. wave has reached that point or passed it, and how long ago. (fact-index.com)
  • Given the inherently complex nature of the pathophysiology of bipolar disorder, this paper aims to capture what is known about the actions of lithium ranging from macroscopic changes in mood, cognition and brain structure, to its effects at the microscopic level on neurotransmission and intracellular and molecular pathways. (springer.com)
  • These results indicate that hGR beta may be a physiologically and pathophysiologically relevant endogenous inhibitor of glucocorticoid action, which may participate in defining the sensitivity of target tissues to glucocorticoids. (jci.org)
  • So it doesn't make it up to the sodium equilibrium potential that's often around positive 50 millivolts. (khanacademy.org)
  • Glucocorticoid receptor beta, a potential endogenous inhibitor of glucocorticoid action in humans. (jci.org)
  • This positive feedback cycle is terminated by sodium channel inactivation that shuts down the channel at depolarised membrane potentials. (els.net)
  • a) The steady‐state inactivation versus voltage relationship (h ∞ ) is generated by measuring the effect of a range of conditioning potentials (-120 to -10 mV) on a test pulse current (test pulse voltage = -20 mV). (els.net)
  • In this video, I want to talk about how action potentials are generated the trigger zone and how they're conducted down the axon. (khanacademy.org)
  • The part of the neuron that consists of the axon where action potentials propagate away from the trigger zone toward the axon endings. (sophia.org)