Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Electrophysiology: 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.Membrane Potentials: 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).Patch-Clamp Techniques: 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.Tetrodotoxin: 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.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Sodium Channels: 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.Calcium: 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.Guinea Pigs: 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.Ventricular Function: The hemodynamic and electrophysiological action of the HEART VENTRICLES.Neurons: 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.Potassium Channels: 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.Neural Conduction: The propagation of the NERVE IMPULSE along the nerve away from the site of an excitation stimulus.Heart: The hollow, muscular organ that maintains the circulation of the blood.Potassium: 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.Heart Conduction System: 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.Papillary Muscles: Conical muscular projections from the walls of the cardiac ventricles, attached to the cusps of the atrioventricular valves by the chordae tendineae.Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.Electric Conductivity: The ability of a substrate to allow the passage of ELECTRONS.4-Aminopyridine: 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.Synaptic Transmission: 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.Microelectrodes: 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)Pyramidal Cells: 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.Heart Ventricles: 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.Dendrites: Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.Purkinje Fibers: Modified cardiac muscle fibers composing the terminal portion of the heart conduction system.Synapses: 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.Potassium Channel Blockers: 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.Tetraethylammonium CompoundsRefractory Period, Electrophysiological: 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 Channels, Voltage-Gated: 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.Anti-Arrhythmia Agents: 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.Myocytes, Cardiac: Striated muscle cells found in the heart. They are derived from cardiac myoblasts (MYOBLASTS, CARDIAC).Models, Cardiovascular: 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.Arrhythmias, Cardiac: 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.Sodium Channel Blockers: 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.Excitatory Postsynaptic Potentials: 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.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Ion Channels: 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.Delayed Rectifier Potassium Channels: 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.Tetraethylammonium: A potassium-selective ion channel blocker. (From J Gen Phys 1994;104(1):173-90)Dogs: 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)Neurons, Afferent: Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM.Evoked Potentials: 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.Calcium Channels: 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.Models, Neurological: 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.Calcium Channels, L-Type: 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.Myocardium: 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.Myocardial Contraction: Contractile activity of the MYOCARDIUM.Heart Atria: The chambers of the heart, to which the BLOOD returns from the circulation.Rats, Sprague-Dawley: 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.Ion Channel Gating: 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.Motor Neurons: Neurons which activate MUSCLE CELLS.Sinoatrial Node: 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).Atrial Function: The hemodynamic and electrophysiological action of the HEART ATRIA.Voltage-Sensitive Dye Imaging: Optical imaging techniques used for recording patterns of electrical activity in tissues by monitoring transmembrane potentials via FLUORESCENCE imaging with voltage-sensitive fluorescent dyes.Endocardium: The innermost layer of the heart, comprised of endothelial cells.Calcium Signaling: 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.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Electrophysiological Phenomena: 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.Hippocampus: 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.Calcium Channel Blockers: A class of drugs that act by selective inhibition of calcium influx through cellular membranes.Neural Inhibition: The function of opposing or restraining the excitation of neurons or their target excitable cells.Interneurons: 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.Pericardium: 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.Anura: 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.Rabbits: 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.Quinidine: 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 Simulation: Computer-based representation of physical systems and phenomena such as chemical processes.Long QT Syndrome: 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.Animals, Newborn: Refers to animals in the period of time just after birth.Presynaptic Terminals: 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.Ether-A-Go-Go Potassium Channels: 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.Reaction Time: The time from the onset of a stimulus until a response is observed.Neurotransmitter Agents: 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.Barium: 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.Cats: 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)Neocortex: 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, Cultured: 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.Lidocaine: 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.Muscle Contraction: 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.Cesium: 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.Ganglia, Spinal: 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.Neuromuscular Junction: The synapse between a neuron and a muscle.gamma-Aminobutyric Acid: The most common inhibitory neurotransmitter in the central nervous system.Electrocardiography: 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.Ventricular Fibrillation: 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.Differential Threshold: The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold.Shal Potassium Channels: 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.Sotalol: An adrenergic beta-antagonist that is used in the treatment of life-threatening arrhythmias.Cardiac Pacing, Artificial: Regulation of the rate of contraction of the heart muscles by an artificial pacemaker.Muscles: Contractile tissue that produces movement in animals.Aminopyridines: Pyridines substituted in any position with an amino group. May be hydrogenated, but must retain at least one double bond.Synaptic Potentials: The voltages across pre- or post-SYNAPTIC MEMBRANES.Strontium: An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.Cnidarian Venoms: 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.Sodium-Calcium Exchanger: 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.Sensory Receptor Cells: 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.Decapodiformes: 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.Biological Clocks: The physiological mechanisms that govern the rhythmic occurrence of certain biochemical, physiological, and behavioral phenomena.Nerve Fibers, Unmyelinated: 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.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Cobalt: 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.Nerve Fibers: 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.Ganglia: Clusters of multipolar neurons surrounded by a capsule of loosely organized CONNECTIVE TISSUE located outside the CENTRAL NERVOUS SYSTEM.Apamin: 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.Nifedipine: A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.Astacoidea: 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.Kinetics: The rate dynamics in chemical or physical systems.Cochlear Nerve: 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.Ranvier's Nodes: 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.Isoproterenol: 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.Procaine: 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).Sciatic Nerve: 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.Egtazic Acid: A chelating agent relatively more specific for calcium and less toxic than EDETIC ACID.Bicuculline: An isoquinoline alkaloid obtained from Dicentra cucullaria and other plants. It is a competitive antagonist for GABA-A receptors.Shaw Potassium Channels: A shaker subfamily that is prominently expressed in NEURONS and are necessary for high-frequency, repetitive firing of ACTION POTENTIALS.Excitatory Amino Acid Antagonists: Drugs that bind to but do not activate excitatory amino acid receptors, thereby blocking the actions of agonists.Periodicity: 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).Peripheral Nerves: 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.Ion Transport: 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.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.Nodose Ganglion: 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.Mechanoreceptors: 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.NAV1.5 Voltage-Gated Sodium Channel: 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.Ulnar Nerve: 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.Barium Compounds: Inorganic compounds that contain barium as an integral part of the molecule.Sarcoplasmic Reticulum: 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.Biophysics: The study of PHYSICAL PHENOMENA and PHYSICAL PROCESSES as applied to living things.Organ Culture Techniques: 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)Fluorescent Dyes: 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.Extracellular Space: 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.GABA Antagonists: Drugs that bind to but do not activate GABA RECEPTORS, thereby blocking the actions of endogenous GAMMA-AMINOBUTYRIC ACID and GABA RECEPTOR AGONISTS.Calcium Channels, T-Type: 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.Median Nerve: 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.Electromyography: Recording of the changes in electric potential of muscle by means of surface or needle electrodes.Cadmium: An element with atomic symbol Cd, atomic number 48, and atomic weight 114. It is a metal and ingestion will lead to CADMIUM POISONING.Leeches: 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.Nervous System Physiological Phenomena: Characteristic properties and processes of the NERVOUS SYSTEM as a whole or with reference to the peripheral or the CENTRAL NERVOUS SYSTEM.6-Cyano-7-nitroquinoxaline-2,3-dione: A potent excitatory amino acid antagonist with a preference for non-NMDA iontropic receptors. It is used primarily as a research tool.Aplysia: 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.Torsades de Pointes: 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.Rhodanine2-Amino-5-phosphonovalerate: 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.Afferent Pathways: Nerve structures through which impulses are conducted from a peripheral part toward a nerve center.Ryanodine: 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.Nerve Endings: 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.Spinal Cord: A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER.Electric Capacitance: The ability of a substrate to retain an electrical charge.KCNQ1 Potassium Channel: A voltage-gated potassium channel that is expressed primarily in the HEART.Electrophysiologic Techniques, Cardiac: Methods to induce and measure electrical activities at specific sites in the heart to diagnose and treat problems with the heart's electrical system.Small-Conductance Calcium-Activated Potassium Channels: 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.Acetanilides: 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, Inwardly Rectifying: Potassium channels where the flow of K+ ions into the cell is greater than the outward flow.Anesthetics, Local: 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.Brain Stem: The part of the brain that connects the CEREBRAL HEMISPHERES with the SPINAL CORD. It consists of the MESENCEPHALON; PONS; and MEDULLA OBLONGATA.Voltage-Gated Sodium Channels: 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.Rana pipiens: 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.Purkinje Cells: The output neurons of the cerebellar cortex.Electrodes: Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum.Nerve Net: 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.Sural Nerve: A branch of the tibial nerve which supplies sensory innervation to parts of the lower leg and foot.NAV1.6 Voltage-Gated Sodium Channel: 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.Acetylcholine: 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.Chlorides: Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.Muscle Cells: 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.Physical Stimulation: Act of eliciting a response from a person or organism through physical contact.Nerve Fibers, Myelinated: 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.Verapamil: A calcium channel blocker that is a class IV anti-arrhythmia agent.Muscle, Smooth: 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)Tubocurarine: A neuromuscular blocker and active ingredient in CURARE; plant based alkaloid of Menispermaceae.Veratridine: A benzoate-cevane found in VERATRUM and Schoenocaulon. It activates SODIUM CHANNELS to stay open longer than normal.Piperidines: A family of hexahydropyridines.KCNQ Potassium Channels: 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.Strophanthidin: 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.Optics and Photonics: 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.Pyridinium CompoundsMollusca: 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.Nociceptors: 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.Mexiletine: Antiarrhythmic agent pharmacologically similar to LIDOCAINE. It may have some anticonvulsant properties.Chelating Agents: Chemicals that bind to and remove ions from solutions. Many chelating agents function through the formation of COORDINATION COMPLEXES with METALS.Vagus Nerve: 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).Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels: 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.Perfusion: Treatment process involving the injection of fluid into an organ or tissue.Kv1.1 Potassium Channel: A delayed rectifier subtype of shaker potassium channels that is commonly mutated in human episodic ATAXIA and MYOKYMIA.Elapid Venoms: 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: 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.Glutamic Acid: A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.Cardiac Electrophysiology: The study of the electrical activity and characteristics of the HEART; MYOCARDIUM; and CARDIOMYOCYTES.Models, Biological: 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.Ganglia, Invertebrate: 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.Rana temporaria: A species of the family Ranidae occurring in a wide variety of habitats from within the Arctic Circle to South Africa, Australia, etc.Cardiac Complexes, Premature: 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, Sympathetic: 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.Sarcolemma: The excitable plasma membrane of a muscle cell. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)Caffeine: 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.QuinoxalinesFerrets: 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.Rana catesbeiana: 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.Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.

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
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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;]
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schmitt at cs.unc.edu (Charles Schmitt) wrote: ,Can anyone suggest what would be good review articles or book (chapters) ,describing how measured postsynaptic spike trains have been observed ,to be dependent on presynaptic spike trains. What Im searching for ,is to strengthen my knowledge of what statistical measures of spike trains, ,such as mean frequency, inter-spike interval, etc..., have been used ,to describe postsynaptic spike trains and how these statistics have any ,observed dependency on the same presynaptic statistics. Im particularly ,interested in such observed dependencies in visual cortex. ,Thanks, Charlie. The initial work here was done for the spinomotor system. A good paper is by Cope, Fetz, and Matsumura, Cross-correlation assessment of synaptic strength of single Ia fibre connections with triceps surae motorneurons in cats, J. Physiol., 390:161-188, 1982. This is not an easy read, at first, but is worth it. (There is an older literature for this system: search Kirkwood, ...
The latency and amplitude of the NMEP are followed closely throughout the surgical period. A 60% decrease in amplitude or a 10% increase in latency is a possible warning sign of spinal cord injury. [11-15] The degree of muscle relaxation can influence the waveform of the neurogenic response through the presence of myogenic artifact contamination or elicited compound muscle action potentials. As demonstrated in the first case, the evoked response being followed had its amplitude increased by a factor of 52 and the latency prolonged by 30%. This high-amplitude, long-latency response directly correlated with the patients degree of muscle relaxation. In both cases, the monitored waveforms returned to a typical neurogenic response appearance within 5 min of an increase in the patients level of neuromuscular blockade. Owen reported, when a patient has two of four muscle twitches (with traditional visual evaluation of train-of-four (TOF) muscle twitch monitoring), the NMEP will contain a myogenic ...
The different time- and voltage-dependence of the ionic currents involved in LQTS may help explain some aspects of the variable phenotype and raise the possibility of gene-specific treatment. Indeed, available data on several hundred genotyped patients indicate the existence of gene-specific differences in the triggers for cardiac events.28 Exercise-related events dominate the clinical picture in IKs-related LQTS (LQT1).28 IKs is the predominant K+ current in conditions of high sympathetic activity, particularly at shorter cycle lengths. Thus, reduced IKs will be predicted to lead to inadequate action potential shortening with adrenergic stress and thereby account for the high prevalence of arrhythmic events in these patients during exercise. By contrast, most LQT3 patients experience events during sleep or at rest; they are also able to markedly shorten their QT interval during exercise.29 In this case, it seems likely that the presence of normal K+ currents produces normal action potential ...
Deformation of neuron structure can induce abnormalities in action potential propagation in nervous system, which is a potential threat from viewpoint of medical science.The effect of geometrical changes and deformation of neuron structure on the propagation of action potential has been studied theoretically. The theoretical model is based on modified cable equation considering spatial changes of the neuron structure, incorporating the different ionic currents components. The results of our analysis reveal that the morphology of the neuron has a significant effect on properties of action potential propagation in the neuron. We have shown that alteration of the velocity of propagation, and the broadening of action potential pulses directly correspond to the changes in the morphology of neuron fiber. The rates of changes in the above mentioned electrophysiological parameters accord with the rate and type of shape deformation ...
40 mV) because each action potential releases only one or a few vesicles rather than the 100 or so vesicles released at the endplate. Activation of neurons depends on temporal summation of many small EPSPs arriving at a high frequency from the same presynaptic neuron and on spatial summation of small EPSPs arriving simultaneously from many presynaptic neurons. In contrast, only a single presynaptic neuron synapses with each muscle cell, every EPP reaches action potential threshold (producing a twitch), and temporal summation of EPPs does not occur (instead, temporal summation of twitches is important). The changes in permeability, expressed in terms of conductance (g), that underlie the action potential in axons are shown in Figure 3-2. The mechanisms 36 CASE FILES: PHYSIOLOGY E Na+ Voltage or conductance Membrane potential + Na + K E K+ 1 ms Figure 3-2. The nerve action potential. The time course of changes in the Na+ and K+ conductance is depicted. for repolarizing the membrane after each ...
We demonstrate here that Kv1 subunit-containing channels are primarily responsible for repolarizing action potentials in the axon collaterals and their presynaptic en passant terminals of layer 5 cortical pyramidal neurons. Furthermore, we observed that subthreshold depolarization of the soma broadened action potentials in axon collaterals, an effect that was blocked with low concentrations of Kv1 channel antagonists. Using simple models with different distributions of D-current, we show that the broadening of action potentials in axon collaterals with subthreshold somatic depolarization requires the presence of Kv1 subunit-containing channels throughout the axon collaterals. Hence, broadening of spikes through the local inactivation of Kv1 channels may play an important role in voltage-dependent modulation of local synaptic transmission (Kole et al., 2007; Shu et al., 2007).. Far from simply disseminating all-or-none impulses from a presynaptic neuron to its targets, the cortical pyramidal ...
What I am confused about is why the action potential goes negative first before then going back up. From my readings online, I thought that the action potentials were meant to go up first then travel down and then continue on its course. If it helps I used a program called audacity to record the action potentials ...
An implantable device applies and controls a neural stimulus. The device has a plurality of electrodes, and a stimulus source for providing a stimulus to be delivered from the electrodes to a neural pathway in order to evoke an action potential on the neural pathway, such as the spinal cord. A control unit controls application of a neural stimulus as defined by a set of parameter values and measures via measurement circuitry an evoked neural compound action potential response. The control unit determines from the measured evoked response a feedback variable, and compares it to a therapy map. The therapy map defines a therapeutic relationship of control variable to feedback variable. One or more of the stimulus parameter values are altered to effect the required change in the control variable. This process is performed iteratively to improve alignment of the feedback variable with the therapy map over time.
This review summarizes estimates for cytoplasmic-free concentrations of Ca,SUP,2+,/SUP, ([Ca,SUP,2+,/SUP,],SUB,i,/SUB,) and Mg,SUP,2+,/SUP, ([Mg,SUP,2+,/SUP,],SUB,i,/SUB,) at rest and during contraction of skeletal muscles, from which substantial quantitative information about them has been accumulated. Although the estimates of resting [Ca,SUP,2+,/SUP,],SUB,i,/SUB, in the literature widely differ, which is because of the variety of difficulties related to different methodologies used, recent studies suggest that estimates of resting [Ca,SUP,2+,/SUP,],SUB,i,/SUB, of approximately 0.05-0.1 μM are likely to be correct. Following action potential propagation, the Ca,SUP,2+,/SUP, release from the sarcoplasmic reticulum causes a transient rise of [Ca,SUP,2+,/SUP,],SUB,i,/SUB, (Ca,SUP,2+,/SUP, transient). The large peak amplitude and brief time course of the Ca,SUP,2+,/SUP, transients have been established only recently by studies with low-affinity Ca,SUP,2+,/SUP, indicators developed in the past ...
Neural computation is energetically expensive, and the brains limited energy supply imposes constraints on its information processing capability. How the brain has evolved to perform computational tasks within these energetic constraints is largely unknown. The theoretical and experimental work in this thesis examines how the white and grey matter - which have different computational roles - balance the trade-off between energy consumption and signalling. In the white matter, I show that the maintenance of cellular resting potentials accounts for the largest portion of signalling-related energy use. Maintaining this cost in myelinating oligodendrocytes outweighs the energetic saving on action potentials that myelin provides, but allows for faster action potential propagation. This design places computational benefit above energetic economy. Nevertheless, I show that action potential propagation in the white matter need not rely on metabolic collaboration of axons with oligodendrocytes, and that ...
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Post 2 in the Crash Course series on how the nervous system works: Action Potential! Neurons are extraordinary cells. Beyond being intricately branched and gigantic relative to most cells, every second hundreds of billions of electrical impulses called action potentials are transmitted in your body. Before we check out how that works, its useful to…
Peripheral neural responses to cochlear stimulation via electrically evoked compound action potentials (ECAPs) of differing pulse distance and interphase gap
Background: A contracting muscle is a source of the plasma K+ concentration increase during physical exercise. The flux of K+ from contracting skeletal muscle to blood is related to the frequency of cells action potential. The elevated blood [K+] may result in the heart rate irregularities and interferes with the way nerves send signals. But plasma increased [K+] recovers rapidly to normal if a regulating mechanism takes action. The aim of this study was to evaluate the participation of processes restoring the balance in blood [K+] after prolonged submaximal exercise. Material/Methods: Nineteen healthy, young, physically active men performed the 120-min submaximal cycling (intensity below individual AT). Measurements were made of urine, plasma and hemolysed whole blood collected before and after a 2-h cycloergometric exercise and after 1h, 2h and also after 24h recovery to quantify the excretion of K+ to urine and the relative contribution of plasma and erythrocytes to the place where K+ is ...
Study Flashcards On physioreview12(Cardiac action potential) at Cram.com. Quickly memorize the terms, phrases and much more. Cram.com makes it easy to get the grade you want!
As in mice, we performed dual optical and electrical recordings to verify the spike trains, this time using whole-cell patch-clamp electrodes to access LN neurons intracellular potentials in intact fly brain explants (Fig. 4C, left). Across 18,141 recorded spikes, the spike trains provided by Ace2N-2AA-mNeon perfectly matched those from the patch-clamp recordings (N = 4 fly brains) and had spike-timing errors of 0.19 ± 0.002 ms (SEM; N = 18,141 spikes), close to the theoretical optimum of 0.11 ± 0.03 ms (Fig. 4C, right). Subthreshold dynamics were readily apparent in the optical traces, including plateau potentials and the rising and falling voltage waveforms surrounding action potentials. Ace2N-2AA-mNeon also reported the submillisecond-scale dynamics of spike back-propagation into the dendritic tree, revealing ~0.5- to 1.0-ms delays between the initiating voltage peak at the soma and those in the dendrites (Fig. 4D and movie S2).. We next imaged olfactory projection neurons (PNs), which ...
Blackrocks highly configurable NeuroPort human neural data acquisition system simultaneously records action potentials and EEG signals.
As the diagram shows, there are three main parts to a neuron: dendritic tree, the soma (cell body), and the axon. The diagram also displays the myelin sheath and the terminal boutons (it calls them buttons), but those are only tangentially pertinent to the discussion of brain waves. The axon is a neurons main method of sending a signal, via what is known as an action potential, to a target cell. The dendritic tree is where most action potentials are received by a neuron, although sometime signals are also received on the soma - this will be important later and discussed in further detail. The junction between an axon and a dendrite is known as a synapse. Neurons generate a resting potential across their cell membranes of approximately -70mV with respect to the surrounding interstitial fluid. For a neuron to fire an action potential it must be excited to below some threshold. Exciting a neuron is typically caused by synapses in the dendritic tree, where an incoming action potential triggers a ...
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I. Characteristic of The Neuron A. Directionality of Electrical Signals B. Integration C. Threshold D. Conduction Velocity E. Plasticity and Reinforcement by Use F. Substructure of a Neuron 1. dendrite 2. soma 3. axon 4. axon hillock 5. myelin sheath 6. synaptic terminals II. Neural Circuits A. PNS vs. CNS B. Sensory Receptors and Effector Organs C. Sensory fibers (input) and Motor neurons (output) D. The simple knee jerk relex arc E. Definitions 1. nuclei 2. ganglia 3. interneurons III. The Basis for the Electrical Signal - The Action Potential A. The Membrane Potential; all cells are more negatively inside B. The Resting Potential C. Na/K ATPase Pump D. Components of the Action Potential - and ionic (channel) basis 1. resting state 2. stimulus 3. depolarization 4. repolarization 5. after hyperpolarization 6. relative and absolute refraction 7. hyperpolarization (generally inhibitory) vs. depolarization (generally excitatory) E. Characteristics of the Action Potential 1. frequency of firing ...
Electrical extracellular recordings, i.e., recordings of the electrical potentials in the extracellular medium between cells, have been a main work-horse in electrophysiology for almost a century. The high-frequency part of the signal (|=500 Hz), i.e., themulti-unit activity (MUA), contains information about the firing of action potentials in surrounding neurons, while the low-frequency part, the local field potential (LFP), contains information about how these neurons integrate synaptic inputs. As the recorded extracellular signals arise from multiple neural processes, their interpretation is typically ambiguous and difficult. Fortunately, a precise biophysical modeling scheme linking activity at the cellular level and the recorded signal has been established: the extracellular potential can be calculated as a weighted sum of all transmembrane currents in all cells located in the vicinity of the electrode. This computational scheme can considerably aid the modeling and analysis of MUA and LFP signals
Action potentials are used in neurons to conduct signals along the axon and occur in electrically excitable cells like neurons and cardiac muscle cells. The action potentials travel in a wave along the membrane causing the voltage sensitive channels to open to allow influx of Na+ thereby causing the conduction of the signal along the axon. The resting membrane potential of cells including neurons is -70mv. An action potential is generated by a change in the membrane potential from -70mv to +40mv when voltage gated ion channels open altering membrane permeability to Na+ and K+. ...
Video created by デューク大学(Duke University) for the course Medical Neuroscience. We now turn our attention from the tangible (human neuroanatomy) to the physiological as we explore the means by which neurons generate, propagate and communicate ...
View Notes - 335-11_lec2 from BIO 335 at SUNY Stony Brook. BIO 335 lecture (2) Action potentials continued. Review first two labs (clickers) Cable properties of the axon - Size & the length
Communication between neurons is of utmost importance for the body to carryout any action. As such, neurons have a unique way of signaling each other. This signaling is accomplished through action potentials. Action potentials are much like electrical signals in that they travel along the axon, like electricity down a wire. The membrane potential of a neuron is maintained by ion concentrations inside and outside the cell. Ion channels open and close to allow ions to pass in and out of the cell to maintain a constant resting membrane potential of -70 mV. Since the membrane is negative, this state is called polarized. When the neuron get stimulated, the sodium channels open and a large influx of sodium ions go into the cell. At this stage, the cell becomes depolarized. This influx of positive charge causes the cells potential to become positive. The spike in charge is called an action potential. Once the potential goes up to roughly +30mV the sodium channels close (Stufflebeam, 2008). Then, the ...
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Action potentials are depolarizations that start at the initial segment of an axon and are propagated toward the synaptic terminals. They are called ...
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I thought myelin sheaths were used to make action potentials move faster, but action potentials dissipate as they move through myelinated areas. The nodes of Ranvier boost action potentials as they have voltage-gated sodium channels that open… Also, action potentials dont actually jump from node to node. They just appear to jump because they move slower at non-insulated areas…. ...
Read "Relationship in Pacemaker Neurons Between the Long-Term Correlations of Membrane Voltage Fluctuations and the Corresponding Duration of the Inter-Spike Interval, The Journal of Membrane Biology" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
A computing system includes an application object, a computer based training instruction object (INSTRUCTION object) and an agent engine. The INSTRUCTION object runs concurrently with the application object. The application objects includes a first action processor and a first command processor. The first action processor receives messages which indicate syntactic actions taken by the user and generates semantic commands based on the syntactic actions. The first command processor receives the semantic commands from the first action processor and executes the semantic commands. The INSTRUCTION object receives input from a user through syntactic actions and displays information on a monitor. The information instructs a user as to operation of the first application. The INSTRUCTION object may include an INSTRUCTION action processor and an INSTRUCTION command processor. The INSTRUCTION action processor receives messages which indicate syntactic actions taken by the user and generates semantic commands
Definition of action potential - the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.
Action potential -- a moving exchange of ions that runs along the length of the axon. So many sodium ions get in that, for a very short time, the difference between the outside and inside of the...
Video shows the graphical representation between action potential and time. A brief explanation is provided here to help you regarding the topic.
There are five main stages of action potential: rising, overshoot, falling, undershoot, and recovery. During the first two stages...
Eventbrite - City of Craft presents Make-Your-Own Light-up Holiday Card with Action Potential Lab - Saturday, 7 December 2019 at The Theatre Centre, Toronto, ON. Find event and ticket information.
Rotors or vortex action potentials with a diameter of about 1 centimeter and a rotation period of about 0.1 second occur in normal myocardium just before transition to fibrillation, a disorderly pattern of action potential propagation. Numerical models and corresponding mathematical analysis have recently suggested candidate mechanisms, all two-dimensional, for this transition from periodic electrical activity to something resembling turbulence. However, comparably recent experiments unanimously show that rotors, and the spiral waves they radiate, remain stably periodic in two-dimensional myocardium. This seeming paradox suggests a transition mediated through disorderly dynamics of the electrical vortex in three dimensions, as a "vortex filament." ...
Video created by Duke University for the course Medical Neuroscience. We now turn our attention from the tangible (human neuroanatomy) to the physiological as we explore the means by which neurons generate, propagate and communicate electrical ...
Video created by Duke University for the course Medical Neuroscience. We now turn our attention from the tangible (human neuroanatomy) to the physiological as we explore the means by which neurons generate, propagate and communicate electrical ...
Author Summary Spike initiation determines how the combined inputs to a neuron are converted to an output. Since the pioneering work of Hodgkin and Huxley, it is known that spikes are generated by the opening of sodium channels with depolarization. According to this standard theory, these channels should open gradually when the membrane potential increases, but spikes measured at the soma appear to suddenly rise from rest. This apparent contradiction has triggered a controversy about the origin of spike
Nanion offers analysis instruments for ion channel analysis, as patch clamp, impedance and bilayer recordings, used for drug development as cardiac safety and basic research.
Fenske S, Mader R, Scharr A, Paparizos C, Cao-Ehlker X, Michalakis S, Shaltiel L, Weidinger M, Stieber J, Feil S, Feil R, Hofmann F, Wahl-Schott C, Biel M. HCN3 contributes to the ventricular action potential waveform in the murine heart. Circ Res 109:1015-1023, 2011 ...
... At rest, the ventricular myocyte membrane potential is about -90 mV, which is close to the potassium reversal potential. When an
Students will demonstrate biophysical knowledge gained in specific areas including membrane properties, voltage and ligand-gated receptors, neurotransmission and mathematical modeling.. ...
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Once a channel is open, the membrane depolarizes at the location on the cellular membrane. Channels, which are next to this open as a result fo the changing potential and the change moves along the membrane opening even more channels. This is called propagation. The potential at which propagation occurs is called teh action potential. It is a go/no go electrical signal, but when the action potential is reached it is all go and the signal will propagate. ...
ANSWER: An action potential is transmitted to the muscle via a motor nerve; the electrical signal is transmitted to the muscle chemically (acetyl choline) across the gap between the nerve and the muscle; an action potential is generated in the muscle; the acetyl choline is broken down and/or taken back up into the nerve ending ...
Nervous System ANS 215 Physiology and Anatomy of Domesticated Animals Nerve Transmission Action potentials are changes in the resting membrane potential that are actively propagated along the membrane
The Senses. Chapter 29. Sensory Input. All senses trigger the same type of action potential The part of the brain that is activated discriminates between the types of stimuli The brain detects sensations and interprets them Action potentials from sensory receptors Slideshow 1722623 by norm
The cell-to-cell propagation of the cardiac action potential allows for the electro-mechanical coupling of cells, which promotes the coordinated contraction of cardiac tissue, often referred to as the heartbeat. The main structures that promote electrical coupling between adjacent cardiac cells are pore-like proteins called... READ MORE ...
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Zalc B, Goujet D, Colman D. The origin of the myelination program in vertebrates. Curr Biol. 2008 Jun 24 18(12):R511-2. doi: 10.1016/j.cub.2008.04.010. p.R511 right column top paragraphPubMed ID18579089 ...
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Student A: I cant wait until the psych test is over. Im so sick of memorizing diagnoses - I mean, Im sorry, but the DSM is just so arbitrary its stupid. Me: Yeah, but until we get a blood test for depression, general consensus of professionals is the best we can do, you know? Student…
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1. Stupid Thymus Ruins Everything. At least, it ruins everything that I already knew about adult x-rays - which was already largely limited to wheres the air, can I use the word hazy to describe this, and no evidence of cardiomegaly But NOT WITH KIDS. With kids, Ive learned the correct answer to even simple…
postlink]http://tvbiologi.blogspot.com/2012/05/electrotonic-and-action-potentials.html[/postlink]http://www.youtube.com/watch?v= ...
Figure 6. Spikes are embedded in unique synapsembles and spatially distributed LFP - The origin of extracellular fields and currents - EEG, ECoG, LFP and spikes
Cell signaling governs basic cellular activities and coordinates cell actions. Cell signaling may help diseases to be treated effectively and cures created.
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 ...
... changing the membrane potential. Thin neurons and axons require less metabolic expense to produce and carry action potentials, ... an all-or-none electrochemical pulse called an action potential is generated and this change in cross-membrane potential ... decreasing the probability of an action potential firing as the voltage becomes more negative (recall that for an action ... The sheath enables action potentials to travel faster than in unmyelinated axons of the same diameter, whilst using less energy ...
... action potentials) to environmental stimuli. These action potentials can influence processes such as actin-based cytoplasmic ... Pickard, B. G. (1973). "Action Potentials in Higher Plants". Botanical Review. 39 (2): 172-201. doi:10.1007/BF02859299. JSTOR ... Zimmermann, M. R.; Maischak, H.; Mithofer, A.; Boland, W.; Felle, H. H. (2009). "System Potentials, a Novel Electrical Long- ... use sophisticated cost-benefit analysis and take tightly controlled actions to mitigate and control diverse environmental ...
... 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 potentialEdit. 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 ...
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 ... Neurotransmitters are chemicals that are released at synapses when an action potential activates them-neurotransmitters attach ...
... 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 ... doi:10.1186/1750-1326-4-20 Barnett MW, Larkman PM; Larkman (June 2007). "The action potential". Pract Neurol 7 (3): 192-7. PMID ... Role and Therapeutic Potential of VEGF in the Nervous System. Physiological Reviews, 89(2), 607-648. doi:10.1152/physrev. ...
In the ventricular action potential, there are 5 phases (labelled 0-4), however pacemaker action potentials don't have an ... This resting phase (see cardiac action potential, phase 4) ends when another action potential reaches the cell. This produces a ... An action potential is a change in voltage (membrane potential) across the membrane of the cell, produced by the movement of ... Once the pacemaker potential reaches a set value, known as the threshold value, it then produces an action potential. Other ...
The results show the appearance of action potential or graded potential spikes. While interpretation of the results requires ... The time difference of the potential is a measure of the time taken for the potential to travel the distance across the two ... The amplitude of the potential, measured baseline to peak, or peak to peak, is a measure of the number of fibers conducting the ... This procedure now analyzes the nerve conduction and muscle potentials through the use of H-Reflex and F-Wave studies. Combined ...
Goel's pieces were Excitaory response; action potential and aspiration. Goel portrays human-human, human-animal and human-place ... action potential (2005) aspiration (2005) "Wool Is 44% Carbon". Leonardo. 45 (2): 186-187. 2012. Retrieved 13 March 2016. " ...
When a neuron fires an action potential, it is initiated at the axon initial segment. An action potential spreads down the axon ... While there is ample evidence to prove the existence of backpropagating action potentials, the function of such action ... 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 ...
Fig 1. A neuronal action potential ("spike"). Note that the amplitude and the exact shape of the action potential can vary ... is the resting potential, and Δ. T. {\displaystyle \Delta _{T}}. is the sharpness of action potential initiation, usually ... is the membrane potential, V. T. {\displaystyle V_{T}}. is the membrane potential threshold, τ. m. {\displaystyle \tau _{m}}. ... The transient thickening of the cell membrane during action potential propagation is also not predicted by these models, nor is ...
Action potentials. Nerve fiber analysis. Awards. Nobel Prize for Physiology or Medicine (1944). Foreign Member of the Royal ... The work led to advances in our knowledge of the mechanism of pain and of reflex action and has inspired a large school of ...
Hodgkin, A. L.; Huxley, A. F. (1939). "Action Potentials Recorded from Inside a Nerve Fibre". Nature. 144 (3651): 710-711. ... With Andrew Fielding Huxley, Hodgkin worked on experimental measurements and developed an action potential theory representing ... With Huxley, he established the propagation mechanism of nerve impulse called "action potentials", the electrical impulses ... 1963 Action Potential Paper[permanent dead link] Imperial War Museum Interview. ...
... blocks action potentials at extremely low concentrations. The site of action of TTX on the sodium channel has been identified. ... "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 ...
Underlying mechanism and threshold for triggered action potentials". Circ. Res. 87: 774-778. doi:10.1161/01.res.87.9.774. Jiang ... causing a prolonged Ca2+ leak which triggers early action potentials. With reduced SR Ca2+ buffering capacity, is a faster ... SOICR leads to spontaneous and inappropriate action potentials, generating arrhythmias. A Ryr2 mutation may increase ...
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, Leona M.; Albuquerque, Edson X. (1978). "Voltage- and time-dependent action of histrionicotoxin on the endplate ...
They react in quick action potentials, especially to vibrations around 250 Hz (even up to centimeters away). They are the most ... They respond in quick action potentials, unlike Merkel. They are responsible for the ability to read Braille and feel gentle ... All of these receptors are activated upon pressures that squish their shape causing an action potential. All afferent touch/ ... "Action Observation Activates Premotor and Parietal Areas in a Somatotopic Manner: An FMRI Study." Wiley Online Library. Jan. ...
Irving Langmuir (1916). "The Relation Between Contact Potentials and Electrochemical Action". Transactions of the American ... The diode possesses a "built-in potential" due to the contact potential difference between the two different materials on ... This charge transfer causes a potential difference between the bodies, which partly cancels the potential originating from the ... but also all the contact potentials due to wiring and so forth around the entire circuit. The sum of all the contact potentials ...
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 ...
Baroreceptor action potentials are relayed to the solitary nucleus, which uses frequency as a measure of blood pressure. ... Active baroreceptors fire action potentials ("spikes") more frequently. The greater the stretch the more rapidly baroreceptors ... fire action potentials. Many individual baroreceptors are inactive at normal resting pressures and only become activated when ...
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" ...
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. ...
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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 ...
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 ... The paper discusses a potential therapeutic strategy involving the upregulation of the dopamine receptor D2R that may be ...
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 ... A great discussion over at Nature Network inspired me to initiate a similar conversation here at Action Potential. Corie Lok ... This is the inaugural post for a new feature at Action Potential. Periodically, we will provide insights from a regional ...
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 ... "All the News Thats Fit to Print" (except the part about potential conflicts of interest). Posted by Noah Gray , Categories: ...
Action Potential. Synchronized Anxiety. 16 Nov 2011 , 18:58 GMT. , Posted by Noah Gray , Category: Other Contributors, SfN ... 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 ... Local field potentials (local activity patterns from many neurons) were recorded from the vHPC, mPFC, dHPC in mice, as well as ...
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 ...
Action Potential. Summer reading. Enough with the cranes already! Richard Powerss 2006 novel The Echo Maker, a National Book ... 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 ...
Action Potential. Awakening dormant genes with cancer drugs. Heres one that first appeared online at the end of last year by ... 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 ...
Action Potential. Serotonin and Motivation for Food Intake = Scis New Hotness. This is a guest post in our #NPGsfn11 blog ... 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 ...
Action Potential. Nature Network Journal Club: Manufacturing new hair cells is for the birds. The next installment of the ... 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 ...
Action Potential. Dissemination before peer review.. The physics community already has theirs. Now biology has its own site ... 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 ...
Action Potential. Nature Neuroscience turns 10!. Our May editorial takes a brief look back at some of the history of Nature ... 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 ...
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 ... From the outset, the reviewers were positive about the potential contribution of this study as it not only demonstrated ... but delving more deeply into the issue we realized that there were also other views both on the potential severity of the ...
Action Potential. "All the News Thats Fit to Print" (except the part about potential conflicts of interest). Since the recent ... 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 ...
Action Potential. Nature Network Journal Club: Getting a GRASP on synapse location. The next installment of the Nature Network ... 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 ...
Action Potential. I Am Judging You While You Wait To Buy Coffee. This is a guest post in our #NPGsfn11 blog series and posted ... 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 ...
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 ...
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 ...
  • 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)
  • Later, his interests expanded to include the genetic origins of inherited arrhythmia syndromes such as long QT, short QT, Brugada, and early repolarization syndromes, as well as the development of potential new treatments for atrial fibrillation (AF). (wikipedia.org)
  • Action potential , the brief (about one-thousandth of a second) reversal of electric polarization of the membrane of a nerve cell ( neuron ) or muscle cell . (britannica.com)
  • In the neuron an action potential produces the nerve impulse, and in the muscle cell it produces the contraction required for all movement. (britannica.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)
  • Find the rate at which the action potentials are produced by the nerve. (bartleby.com)
  • As an action potential (nerve impulse) travels down an axon there is a change in polarity across the membrane of the axon. (wikipedia.org)
  • 8%) (prolonged sensory response latency, slower sensory conduction velocity, non-obtained sensory nerve action potential , etc. (thefreedictionary.com)
  • 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)
  • The action potential pulse model has many advantages over the simpler Hodgkin Huxley version including evidence, efficiency, timing entropy measurements, and the explanation of nerve impulse flow through myelinated axons. (wikipedia.org)
  • The spike potentials last 10 to 40 times as long in gastrointestinal muscle as the action potentials in large nerve fibers, each gastrointestinal spike lasting as long as 10 to 20 milliseconds. (wikipedia.org)
  • In 1939, reporting work done in Plymouth, Alan Hodgkin and Andrew Huxley published a short paper in the journal Nature announcing their achievement of recording action potentials from inside a nerve fibre. (wikipedia.org)
  • With Huxley, he established the propagation mechanism of nerve impulse called "action potentials", the electrical impulses which enable the activity of an organism to be coordinated by a central nervous system. (wikipedia.org)
  • The soliton hypothesis in neuroscience is a model that claims to explain how action potentials are initiated and conducted along axons based on a thermodynamic theory of nerve pulse propagation. (wikipedia.org)
  • The measurement of a temperature pulse and the claimed absence of heat release during an action potential were the basis of the proposal that nerve impulses are an adiabatic phenomenon much like sound waves. (wikipedia.org)
  • An action potential traveling along a mixed nerve results in a slight increase in temperature followed by a decrease in temperature. (wikipedia.org)
  • When a muscle contracts, an action potential is propagated down a nerve until it reaches the axon terminal of the motor neuron. (wikipedia.org)
  • It was originally developed by Robert Stämpfli for recording action potentials in nerve fibers, and is particularly useful for measuring irreversible or highly variable pharmacological modifications of channel properties since untreated regions of membrane can be pulled into the node between the sucrose regions. (wikipedia.org)
  • The method was used to study action potentials in nerve fibers. (wikipedia.org)
  • The auditory nerve action potential is the most widely studied component in ECochG. (wikipedia.org)
  • 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)
  • Although the material discussed is of general applicability to point processes, attention will be confined to sequences of neuronal action potentials (spike trains), the motivation for this work. (nih.gov)
  • In addition, a growing number of flavonoids have been shown to inhibit the development of Alzheimer disease (AD)-like pathology and to reverse deficits in cognition in rodent models, suggestive of potential therapeutic utility in dementia. (nih.gov)
  • The purpose of these spontaneous action potentials is to inhibit targets of the basal ganglia, and decreases in inhibition are associated with movement. (wikipedia.org)
  • Lithium has antidepressant properties, but does not inhibit muricidal behavior, which suggests a potential limitation against using it as an antidepressant screening test. (wikipedia.org)
  • We demonstrate noninvasive detection of action potentials with single-neuron sensitivity, including in whole organisms. (pnas.org)