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.Purkinje Fibers: Modified cardiac muscle fibers composing the terminal portion of the heart conduction system.Purkinje Cells: The output neurons of the cerebellar cortex.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.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.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)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).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.Sheep: Any of the ruminant mammals with curved horns in the genus Ovis, family Bovidae. They possess lachrymal grooves and interdigital glands, which are absent in GOATS.Heart: The hollow, muscular organ that maintains the circulation of the blood.Myocytes, Cardiac: Striated muscle cells found in the heart. They are derived from cardiac myoblasts (MYOBLASTS, CARDIAC).Cerebellum: The part of brain that lies behind the BRAIN STEM in the posterior base of skull (CRANIAL FOSSA, POSTERIOR). It is also known as the "little brain" with convolutions similar to those of CEREBRAL CORTEX, inner white matter, and deep cerebellar nuclei. Its function is to coordinate voluntary movements, maintain balance, and learn motor skills.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.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)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.Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.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.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.Myocardial Contraction: Contractile activity of the MYOCARDIUM.Cerebellar Cortex: The superficial GRAY MATTER of the CEREBELLUM. It consists of two main layers, the stratum moleculare and the stratum granulosum.Impulse Control Disorders: Disorders whose essential features are the failure to resist an impulse, drive, or temptation to perform an act that is harmful to the individual or to others. Individuals experience an increased sense of tension prior to the act and pleasure, gratification or release of tension at the time of committing the act.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Time Factors: Elements of limited time intervals, contributing to particular results or situations.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.Cardiac Output: The volume of BLOOD passing through the HEART per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with STROKE VOLUME (volume per beat).Muscle Fibers, Skeletal: Large, multinucleate single cells, either cylindrical or prismatic in shape, that form the basic unit of SKELETAL MUSCLE. They consist of MYOFIBRILS enclosed within and attached to the SARCOLEMMA. They are derived from the fusion of skeletal myoblasts (MYOBLASTS, SKELETAL) into a syncytium, followed by differentiation.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.Dietary Fiber: The remnants of plant cell walls that are resistant to digestion by the alimentary enzymes of man. It comprises various polysaccharides and lignins.Ventricular Function: The hemodynamic and electrophysiological action of the HEART VENTRICLES.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.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.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.Cardiac Glycosides: Cyclopentanophenanthrenes with a 5- or 6-membered lactone ring attached at the 17-position and SUGARS attached at the 3-position. Plants they come from have long been used in congestive heart failure. They increase the force of cardiac contraction without significantly affecting other parameters, but are very toxic at larger doses. Their mechanism of action usually involves inhibition of the NA(+)-K(+)-EXCHANGING ATPASE and they are often used in cell biological studies for that purpose.Benzocaine: A surface anesthetic that acts by preventing transmission of impulses along NERVE FIBERS and at NERVE ENDINGS.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.Papillary Muscles: Conical muscular projections from the walls of the cardiac ventricles, attached to the cusps of the atrioventricular valves by the chordae tendineae.Electric Conductivity: The ability of a substrate to allow the passage of ELECTRONS.Cardiac Pacing, Artificial: Regulation of the rate of contraction of the heart muscles by an artificial pacemaker.Digitalis Glycosides: Glycosides from plants of the genus DIGITALIS. Some of these are useful as cardiotonic and anti-arrhythmia agents. Included also are semi-synthetic derivatives of the naturally occurring glycosides. The term has sometimes been used more broadly to include all CARDIAC GLYCOSIDES, but here is restricted to those related to Digitalis.Nisoldipine: A dihydropyridine calcium channel antagonist that acts as a potent arterial vasodilator and antihypertensive agent. It is also effective in patients with cardiac failure and angina.Cardiac Surgical Procedures: Surgery performed on the heart.Ouabain: A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.Death, Sudden, Cardiac: Unexpected rapid natural death due to cardiovascular collapse within one hour of initial symptoms. It is usually caused by the worsening of existing heart diseases. The sudden onset of symptoms, such as CHEST PAIN and CARDIAC ARRHYTHMIAS, particularly VENTRICULAR TACHYCARDIA, can lead to the loss of consciousness and cardiac arrest followed by biological death. (from Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005)Minke Whale: The species Balaenoptera acutorostrata, in the family Balaenopteridae. It is the smallest of the WHALES in the family and though mainly oceanic, is often found in coastal waters including bays and estuaries.Endocardium: The innermost layer of the heart, comprised of endothelial cells.Bundle of His: Small band of specialized CARDIAC MUSCLE fibers that originates in the ATRIOVENTRICULAR NODE and extends into the membranous part of the interventricular septum. The bundle of His, consisting of the left and the right bundle branches, conducts the electrical impulses to the HEART VENTRICLES in generation of MYOCARDIAL CONTRACTION.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.Gallopamil: Coronary vasodilator that is an analog of iproveratril (VERAPAMIL) with one more methoxy group on the benzene ring.Mice, Neurologic Mutants: Mice which carry mutant genes for neurologic defects or abnormalities.Refractory 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.Neural Conduction: The propagation of the NERVE IMPULSE along the nerve away from the site of an excitation stimulus.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.Mineral Fibers: Long, pliable, cohesive natural or manufactured filaments of various lengths. They form the structure of some minerals. The medical significance lies in their potential ability to cause various types of PNEUMOCONIOSIS (e.g., ASBESTOSIS) after occupational or environmental exposure. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p708)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.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).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.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.Muscle Fibers, Fast-Twitch: Skeletal muscle fibers characterized by their expression of the Type II MYOSIN HEAVY CHAIN isoforms which have high ATPase activity and effect several other functional properties - shortening velocity, power output, rate of tension redevelopment. Several fast types have been identified.Muscle Fibers, Slow-Twitch: Skeletal muscle fibers characterized by their expression of the Type I MYOSIN HEAVY CHAIN isoforms which have low ATPase activity and effect several other functional properties - shortening velocity, power output, rate of tension redevelopment.Dioxanes: 1,4-Diethylene dioxides. Industrial solvents. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985), dioxane itself may "reasonably be anticipated to be a carcinogen." (Merck Index, 11th ed)Aminopyridines: Pyridines substituted in any position with an amino group. May be hydrogenated, but must retain at least one double bond.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.Aequorin: A photoprotein isolated from the bioluminescent jellyfish Aequorea. It emits visible light by an intramolecular reaction when a trace amount of calcium ion is added. The light-emitting moiety in the bioluminescence reaction is believed to be 2-amino-3-benzyl-5-(p-hydroxyphenyl)pyrazine (AF-350).Dendrites: Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.Cotton Fiber: A TEXTILE fiber obtained from the pappus (outside the SEEDS) of cotton plant (GOSSYPIUM). Inhalation of cotton fiber dust over a prolonged period can result in BYSSINOSIS.Connexins: A group of homologous proteins which form the intermembrane channels of GAP JUNCTIONS. The connexins are the products of an identified gene family which has both highly conserved and highly divergent regions. The variety contributes to the wide range of functional properties of gap junctions.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.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)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.Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.Incubators: Insulated enclosures in which temperature, humidity, and other environmental conditions can be regulated at levels optimal for growth, hatching, reproduction, or metabolic reactions.Kinetics: The rate dynamics in chemical or physical systems.Myofibrils: The long cylindrical contractile organelles of STRIATED MUSCLE cells composed of ACTIN FILAMENTS; MYOSIN filaments; and other proteins organized in arrays of repeating units called SARCOMERES .Tolazamide: A sulphonylurea hypoglycemic agent with actions and uses similar to those of CHLORPROPAMIDE.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.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.Fur Seals: A group comprised of several species of eared seals found in two genera, in the family Otariidae. In comparison to SEA LIONS, they have an especially dense wooly undercoat.Chlorides: Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.Barium Compounds: Inorganic compounds that contain barium as an integral part of the molecule.Halothane: A nonflammable, halogenated, hydrocarbon anesthetic that provides relatively rapid induction with little or no excitement. Analgesia may not be adequate. NITROUS OXIDE is often given concomitantly. Because halothane may not produce sufficient muscle relaxation, supplemental neuromuscular blocking agents may be required. (From AMA Drug Evaluations Annual, 1994, p178)Disopyramide: A class I anti-arrhythmic agent (one that interferes directly with the depolarization of the cardiac membrane and thus serves as a membrane-stabilizing agent) with a depressant action on the heart similar to that of guanidine. It also possesses some anticholinergic and local anesthetic properties.Cerebellar Nuclei: Four clusters of neurons located deep within the WHITE MATTER of the CEREBELLUM, which are the nucleus dentatus, nucleus emboliformis, nucleus globosus, and nucleus fastigii.Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.Muscles: Contractile tissue that produces movement in animals.Neurons, Afferent: Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM.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.Strontium: An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.Cardiomegaly: Enlargement of the HEART, usually indicated by a cardiothoracic ratio above 0.50. Heart enlargement may involve the right, the left, or both HEART VENTRICLES or HEART ATRIA. Cardiomegaly is a nonspecific symptom seen in patients with chronic systolic heart failure (HEART FAILURE) or several forms of CARDIOMYOPATHIES.Procainamide: A class Ia antiarrhythmic drug that is structurally-related to PROCAINE.Cardiac Tamponade: Compression of the heart by accumulated fluid (PERICARDIAL EFFUSION) or blood (HEMOPERICARDIUM) in the PERICARDIUM surrounding the heart. The affected cardiac functions and CARDIAC OUTPUT can range from minimal to total hemodynamic collapse.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.Biological Transport, Active: The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.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.Heart Atria: The chambers of the heart, to which the BLOOD returns from the circulation.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.Heart Diseases: Pathological conditions involving the HEART including its structural and functional abnormalities.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.Acetohexamide: A sulfonylurea hypoglycemic agent that is metabolized in the liver to 1-hydrohexamide.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.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.Atrioventricular Node: A small nodular mass of specialized muscle fibers located in the interatrial septum near the opening of the coronary sinus. It gives rise to the atrioventricular bundle of the conduction system of the heart.Epinephrine: The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS.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.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.Mexiletine: Antiarrhythmic agent pharmacologically similar to LIDOCAINE. It may have some anticonvulsant properties.Myocardial Infarction: NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION).Propranolol: A widely used non-cardioselective beta-adrenergic antagonist. Propranolol has been used for MYOCARDIAL INFARCTION; ARRHYTHMIA; ANGINA PECTORIS; HYPERTENSION; HYPERTHYROIDISM; MIGRAINE; PHEOCHROMOCYTOMA; and ANXIETY but adverse effects instigate replacement by newer drugs.Olivary Nucleus: A part of the MEDULLA OBLONGATA situated in the olivary body. It is involved with motor control and is a major source of sensory input to the CEREBELLUM.Sodium Cyanide: A highly poisonous compound that is an inhibitor of many metabolic processes and is used as a test reagent for the function of chemoreceptors. It is also used in many industrial processes.Veratridine: A benzoate-cevane found in VERATRUM and Schoenocaulon. It activates SODIUM CHANNELS to stay open longer than normal.Cardiac Catheterization: Procedures in which placement of CARDIAC CATHETERS is performed for therapeutic or diagnostic procedures.Myosin Heavy Chains: The larger subunits of MYOSINS. The heavy chains have a molecular weight of about 230 kDa and each heavy chain is usually associated with a dissimilar pair of MYOSIN LIGHT CHAINS. The heavy chains possess actin-binding and ATPase activity.Heart Block: Impaired conduction of cardiac impulse that can occur anywhere along the conduction pathway, such as between the SINOATRIAL NODE and the right atrium (SA block) or between atria and ventricles (AV block). Heart blocks can be classified by the duration, frequency, or completeness of conduction block. Reversibility depends on the degree of structural or functional defects.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Verapamil: A calcium channel blocker that is a class IV anti-arrhythmia agent.Stress Fibers: Bundles of actin filaments (ACTIN CYTOSKELETON) and myosin-II that span across the cell attaching to the cell membrane at FOCAL ADHESIONS and to the network of INTERMEDIATE FILAMENTS that surrounds the nucleus.Rubidium: An element that is an alkali metal. It has an atomic symbol Rb, atomic number 37, and atomic weight 85.47. It is used as a chemical reagent and in the manufacture of photoelectric cells.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Chick Embryo: The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.Animals, Newborn: Refers to animals in the period of time just after birth.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.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.
... conduction system of the heart by transmitting cardiac action potentials from the bundle of His to the Purkinje fibers. There ... it may cease to conduct electrical impulses appropriately, resulting in altered pathways for ventricular depolarization. This ... These structures lead to a network of thin filaments known as Purkinje fibers. They play an integral role in the electrical ... conduction system of the heart by transmitting cardiac action potentials to the Purkinje fibers. When a bundle branch or ...
Every cardiac cell is able to transmit impulses of excitation in every direction but will do so only once within a short time. ... These cells are found in the conduction system of the heart and include the SA node, AV node, Bundle of His and Purkinje fibers ... Automaticity refers to a cardiac muscle cell firing off an impulse on its own. All of the cells in the heart have the ability ... Not all the electrical impulses of the heart produce audible or palpable beats; in many cardiac arrhythmias, the premature or ...
The Purkinje fibers are additional myocardial conductive fibers that spread the impulse to the myocardial contractile cells in ... The Purkinje fibers have a fast inherent conduction rate, and the electrical impulse reaches all of the ventricular muscle ... The bundle branches would have an inherent rate of 20-30 impulses per minute, and the Purkinje fibers would fire at 15-20 ... Both bundle branches descend and reach the apex of the heart where they connect with the Purkinje fibers. This passage takes ...
During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from both ... the Purkinje fibers are distinctly shielded from each other by collagen or the cardiac skeleton. The Purkinje fibers are ... Purkinje fibers are a unique cardiac end-organ. Further histologic examination reveals that these fibers are split in ... The Purkinje fibers (/pərˈkɪndʒiː/ pər-KIN-jee) (Purkinje tissue or subendocardial branches) are located in the inner ...
These bundles and fascicles give rise to thin filaments known as Purkinje fibers. These fibers distribute the impulse to the ... a novel approach to cardiac pacing in patients with normal His-Purkinje activation". Circulation. 101 (8): 869-77. doi:10.1161/ ... The fascicular branches then lead to the Purkinje fibers, which provide electrical conduction to the ventricles, causing the ... These specialized muscle fibers in the heart were named after the Swiss cardiologist Wilhelm His, Jr., who discovered them in ...
Purkinje fibers are occasionally capable of acting as the default or "escape" pacemaker. The reason Purkinje cells do not ... The contraction of cardiac muscle (heart muscle) in all animals is initiated by electrical impulses known as action potentials ... The rate at which these impulses fire controls the rate of cardiac contraction, that is, the heart rate. The cells that create ... Cardiac arrhythmias can cause heart block, in which the contractions lose any useful rhythm. In humans, and occasionally in ...
Every cardiac cell is able to transmit impulses of excitation in every direction but will do so only once within a short time. ... These cells are found in the conduction system of the heart and include the SA node, AV node, Bundle of His and Purkinje fibers ... Automaticity refers to a cardiac muscle cell firing off an impulse on its own. All of the cells in the heart have the ability ... Tachycardia that is not sinus tachycardia usually results from the addition of abnormal impulses to the normal cardiac cycle. ...
These purkinje fibers (p-fibers) found in the hearts moderator bands are a specialized cardiac muscle fiber that causes the ... It functions to carry the electrical impulse from the atria to the ventricle. Upon view, the myocardial cells are observed to ... Parto, P.; Tadjalli, M.; Ghazi, S. R. & Salamat, M. A. (2013). "Distribution and Structure of Purkinje Fibers in the Heart of ... Moderator bands, full of purkinje fibers, are found in different locations in the left and right ventricles. These bands are ...
Tsien, R. W.; Carpenter, D. O. (1978-06-01). "Ionic mechanisms of pacemaker activity in cardiac Purkinje fibers". Federation ... they are depolarized by the oncoming impulse from the SAN This is called "overdrive suppression". Pacemaker activity of these ... Rate dependence of the action potential is a fundamental property of cardiac cells and alterations can lead to severe cardiac ... Interactive animation illustrating the generation of a cardiac action potential Interactive mathematical models of cardiac ...
"Cardiac Muscle Fibers". ZY 560 Mammalian Physiology. Auburn University. Archived from the original on June 1, 2005. Retrieved ... If SA nodal impulses occur at a rate less than 60bpm, the heart rhythm is known as sinus bradycardia. If SA nodal impulses ... The two bundle branches taper out to produce numerous Purkinje fibers, which stimulate individual groups of myocardial cells to ... the stimulus diverges and is conducted through the left and right bundle of His to the respective Purkinje fibers for each side ...
At the end of the bundle branches, the electrical impulse goes into the ventricular muscle through the Purkinje Fibers. This is ... These cells start an electrical impulse. This electrical impulse sets the rate and timing at which all cardiac muscle cells ... Cardiac and cardio both mean "about the heart", so if something has the prefix cardio or cardiac, it has something to do with ... After the electrical impulse goes through the AV Node, the electrical impulse will go through the conduction system of the ...
... the stimulus travels through the bundle of His to the left and right bundle branches and then to the Purkinje fibers and the ... Since the accessory pathway does not have the impulse slowing properties of the AV node, the electrical impulse first activates ... Rarely cardiac arrest may occur. The most common type of irregular heartbeat that occurs is known as paroxysmal ... The short PR interval and slurring of the QRS complex are reflective of the impulse making it to the ventricles early (via the ...
He credited Tawara for connecting the bundle with the Purkinje fibers and for declaring it the heart's conduction system. ... It has been recognized by cardiologists as a monumental discovery, and a milestone in cardiac electrophysiology". The monograph ... conduction of excitation impulses surely must take place there." On 26 September 1905, shortly before the monograph was due to ... and descends into the terminal ends of the Purkinje fibers. Tawara commented that the system represents a transporting or ...
"Ionic mechanisms of pacemaker activity in cardiac Purkinje fibers". Federation Proceedings. 37 (8): 2127-2131. ISSN 0014-9446. ... If the SA node does not function, or the impulse generated in the SA node is blocked before it travels down the electrical ... Other cells within the heart (including the purkinje fibers and atrioventricular node; AVN) can also initiate action potentials ... Action potentials pass from one cardiac cell to the next through pores known as gap junctions. These gap junctions are made of ...
... current before it is conducted below the atria and through the circuits known as the bundle of His and the Purkinje fibers-all ... The sinoatrial node, often known as the cardiac pacemaker, is the point of origin for producing a wave of electrical impulses ... Cardiac output. References[edit]. *^ "19.3 Cardiac Cycle , Anatomy & Physiology". library.open.oregonstate.edu. Retrieved 2018- ... The cardiac cycle and Wiggers diagram[edit]. A Wiggers diagram illustrate events and details of the cardiac cycle with ...
Ultimately, the fascicles divide into millions of Purkinje fibres, which in turn interdigitise with individual cardiac myocytes ... through muscle fibers in a way that both slows the electrical movement and changes the directional propagation of the impulses ... The impulse travels next through the left and right atria and summates at the atrioventricular node. From the AV node the ... Cardiac pacemaker Heart block First degree AV block Second degree AV block Third degree AV block Cecil Textbook of Medicine. W. ...
Reentry occurs when an area of 1-way block in the Purkinje fibers and a second area of slow conduction are present. This ... However, when a PVC occurs the impulse nearly always travels through only one bundle fiber, so there is no neutralization ... Magnesium in Cardiac Arrhythmias (MAGICA) Investigators". Journal of the American College of Cardiology. 29 (5): 1028-34. doi: ... is a relatively common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the ...
ezi cells ziqala i-electrical impulse. Le electrical impulse ibeka umyinge nexesha emazifinyele ngalo ii-cells ze-cardiac ... ukubetha kwentliziyo kuhamba kuye kungena kwizihlunu ze-ventricular nge-Purkinje Fibers. Yiyo ke lento yenza okokuba i- ... Le knqubo ke kuthiwa yi-cardiac diastole Zilandelelana ngolu hlobo: i-atrial systole → i-ventricular systole → i-cardiac ... Amagama athi cardiac kunye ne-cardio omabini athetha nge"ntliziyo", ngoko ke ukuba into inesimaphambili esingu-cardio or ...
"Purkinje Fibers". About.com. 9 April 2012. Archived from the original on 14 April 2012. Retrieved 7 June 2012. Guyton & Hall ... the unique ability to initiate a cardiac action potential at a fixed rate - spreading the impulse rapidly from cell to cell to ... The cardiac output is normalized to body size through body surface area and is called the cardiac index. The average cardiac ... the middle cardiac vein (draining the bottom of the left and right ventricles), and small cardiac veins. The anterior cardiac ...
In the simpler case of adjacent fibers that experience simultaneous stimulation the impulse is slowed because both fibers are ... It was demonstrated in this study that the basket cells which encapsulate some regions of Purkinje fibers can cause inhibitory ... The role of ephaptic coupling in cardiac cells is becoming more apparent. One author even goes so far as to say, "While ... The firing of these basket cells, which occurs more rapidly than in the Purkinje cells, draws current across the Purkinje cell ...
Note that these Purkinje fibers are muscle fibers and not related to the Purkinje cells, which are neurons found in the ... Kléber AG, Rudy Y (April 2004). "Basic mechanisms of cardiac impulse propagation and associated arrhythmias". Physiol. Rev. 84 ... Action potentials from the AV node travel through the bundle of His and thence to the Purkinje fibers. Conversely, anomalies in ... Tasaki I (1939). "Electro-saltatory transmission of nerve impulse and effect of narcosis upon nerve fiber". Am. J. Physiol. 127 ...
Note that these Purkinje fibers are muscle fibers and not related to the Purkinje cells, which are neurons found in the ... "Basic mechanisms of cardiac impulse propagation and associated arrhythmias". Physiol. Rev. 84 (2): 431-88. doi:10.1152/physrev. ... Cardiac action potentialsEdit. Main articles: Cardiac action potential, Electrical conduction system of the heart, Cardiac ... Action potentials from the AV node travel through the bundle of His and thence to the Purkinje fibers.[note 2] Conversely, ...
... passes through the atrioventricular node down into the bundle of His and into the Purkinje fibers, spreading down and to the ... Cardiac stress test Bruce protocol. Electrophysiology study. Cardiac imaging. Angiocardiography. Echocardiography TTE. TEE. ... This interval reflects the time the electrical impulse takes to travel from the sinus node through the AV node. A PR interval ... Main article: Cardiac electrophysiology. The formal study of the electrical conduction system of the heart is called cardiac ...
Cardiac gap junctions can pharmacologically be opened with rotigaptide. A gap junction located in neurons is often referred to ... They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass ... Gruijters, WTM; Kistler, J; Bullivant, S; Goodenough, DA (1987). "Immunolocalization of MP70 in lens fiber 16-17-nm ... and in the cerebellum between Purkinje neurons and Bergmann glial cells. It appears that astrocytes are coupled by gap ...
These purkinje fibers (p-fibers) found in the hearts moderator bands are a specialized cardiac muscle fiber that causes the ... It functions to carry the electrical impulse from the atria to the ventricle. Upon view, the myocardial cells are observed to ... Moderator bands, full of purkinje fibers, are found in different locations in the left and right ventricles.[68] These bands ... Parto, P.; Tadjalli, M.; Ghazi, S. R. & Salamat, M. A. (2013). "Distribution and Structure of Purkinje Fibers in the Heart of ...
Purkinje fibers Specialized cardiac cells in subendocardium - rapidly depolarize. -transmit impulse through myocardium ... cardiac muscle fibers-. located in myocardium of heart & proximal portion of pulmonary veins ... 3. Muscle Fibers (myocyte)- endomysium;type III. 4. Fascicles (bundle of muscle fibers)-Perimysium typeI. 5. Muscle- Epimysium ... Skeletal/Cardiac muscle damage releases TROPONIN and MYOGLOBIN into blood. -excess Mb in blood after skeletal muscle injury ...
During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from the ... Purkinje Fibers[edit]. Purkinje fibers (or Purkyne tissue) are located in the inner ventricular walls of the heart, just ... The bundles give rise to thin filaments known as Purkinje fibers. These fibers distribute the impulse to the ventricular muscle ... The SA node emits a new impulse before either the AV or purkinje fibers reach threshold. The sinoatrial node (SA node) is a ...
Fibers that show a high resting potential cannot be excited except by depolarizing stimuli strong enough to move the membrane ... Fibers that show a low resting potential are more easily excited and may show rhythmic activity sustained by afterpotentials ... The membrane potential of these fibers can be switched from -50 mV to -90 mV by a hyperpolarizing current pulse and from -90 mV ... A reduction in potassium conductance causes the fiber to depolarize from -90 mV to -50 mV because of the presence of an inward ...
The Purkinje fibers are additional myocardial conductive fibers that spread the impulse to the myocardial contractile cells in ... The Purkinje fibers have a fast inherent conduction rate, and the electrical impulse reaches all of the ventricular muscle ... The bundle branches would have an inherent rate of 20-30 impulses per minute, and the Purkinje fibers would fire at 15-20 ... Both bundle branches descend and reach the apex of the heart where they connect with the Purkinje fibers. This passage takes ...
2. large, clear, tightly packed, impulse-conducting cells of the cardiac Purkinje fibers. ... basket cell a neuron of the cerebral cortex whose fibers form a basket-like nest in which a Purkinje cell rests. ... Purkinje cell. See: Purkinje, Johannes E. von. pus cell. A leukocyte present in pus. Pus cells are often degenerated or ... muscle cell see under fiber. myoid cells cells in the seminiferous tubules which are presumed to be contractile and to be ...
delivers impulse from R to L atrium 65 Bundle of His and Purkinje fibers ... like with CAD, hypertensive cardiac disease, pulmonic disease, history of MI or CABG ... Study Cardiac Anatomy flashcards from Chaeli Greco ... ventrical myocardium similar to type I fibers but have more ...
Their function is to send nerve impulses to the cells in the ventricles of the heart and cause... ... Purkinje fibers are special fibers that are located in the atrioventricular, or AV, bundle of the heart. ... Theyre made up of specialized cardiomyocytes, which are the cells that make up cardiac muscle. These special cells found in ... It sends impulses down the septum through the AV bundle branches to the Purkinje fibers. ...
Demonstrating purkinje fibers, the modified cardiac muscle fibers which occur on the periphery of the cell. These fibers ... Heart, Purkinje Fibers. Iron Hematoxylin. Section. Each. Retrieving. The minimum order for this item is . ...
During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from both ... the Purkinje fibers are distinctly shielded from each other by collagen or the cardiac skeleton. The Purkinje fibers are ... Purkinje fibers are a unique cardiac end-organ. Further histologic examination reveals that these fibers are split in ... The Purkinje fibers (/pərˈkɪndʒiː/ pər-KIN-jee) (Purkinje tissue or subendocardial branches) are located in the inner ...
Local stimulation by a brief electrical shock of adequate strength generates an impulse that propagates in a regenerative... ... Cardiac muscle, like skeletal muscle and nerves, is electrically excitable. ... Tsien, R. W. Effects of epinephrine on the pacemaker current of cardiac Purkinje fibers. J. Gen Physiol. 64: 293-319, 1974. ... Kass R.S., Bennett P.B. (1985) Microelectrode Voltage Clamp: The Cardiac Purkinje Fiber. In: Smith T.G., Lecar H., Redman S.J ...
The left ventricle contracts, as it receives impulses from the Purkinje fibers [47]. Oxygenated blood is pumped into the aorta ... Cardiac Output. Cardiac output (CO) is the quantity of blood or volume of blood that is pumped by the heart per minute. Cardiac ... the right ventricle contracts as it receives impulses from the Purkinje fibers [42]. The semi lunar valves get opened and the ... Cardiac cycle. The sequence of events that occurs when the heart beats, is known as "cardiac cycle". The frequency of the ...
... any of the specialized cardiac muscle fibers forming a network in the ventricular walls that conduct electric impulses ... purkinje fiber. in Medicine. Purkinje fiber. n.. *Any of the specialized cardiac muscle fibers, part of the impulse-conducting ... any of the specialized cardiac muscle fibers forming a network in the ventricular walls that conduct electric impulses ... Origin of Purkinje fiber. named after Jan Evangelista Purkinje (Czech Purkyně) (1787-1869), Czech physiologist, who discovered ...
Purkinje fibers are specialized muscle fibers in the heart that relay impulses from the atrioventricular bundle to the ... the purkinje fibers). The impulse travels so swiftly along this specialized pathway that all of the cardiac muscle cells in the ... The Purkinje fibers come off of the bundle branches to bring the impulse deep into the muscle tissue. Picture something like a ... When an electrical impulse is sent along the Purkinje fibers, it is rapidly relayed to the ventricular cells on both sides of ...
The cardiac cycle is the sequence of pumping and filling that happens from the start of a heartbeat to its finish. The steps in ... The Purkinje fibers cause the ventricle to contract, or go into the first stage of systole in the cardiac cycle, and pump the ... An electrical impulse from the sinoatrial (SA) node tells the atrium to contract and push in the remaining blood and signals to ... The left ventricle then gets the message from the Purkinje fibers to contract, or go into the second stage of systole. This ...
Finally, the Purkinje fibers conduct the impulse from the apex of the heart up the ventricular myocardium, and then the ... Cardiac Arrest, Cardiac Cycle, Cardiac Muscle, Cardiomyocyte, Circulatory System, Coronary Artery, Coronary Vein, Diastole, ECG ... This information can be observed as an electrocardiogram (ECG)-a recording of the electrical impulses of the cardiac muscle. ... an internal implant that sends an electrical impulse through the heart. *the excitation of cardiac muscle cells at the ...
... significantly improving the ability of the monitor to cutaneously sense cardiac electrical potential signals, particularly the ... depolarization impulse transits the Bundle of His and moves into the right and left bundle branches as well as Purkinje fibers ... As cardiac-based syncope is associated with the highest mortality rate, the distinction between cardiac-based syncope and both ... Moreover, both cardiac-based and neurally mediated syncope episodes may require a different treatments. For cardiac arrhythmia- ...
... and Purkinje fibers. The SA node is the primary pacemaker from which the electrical impulse moves to the AV node then, by way ... 2) As in mammals, birds have a cardiac conduction system that consists of a sinoatrial (SA) node, an AV node, ... 3) The Purkinje fibers of birds follow the coronary arteries and, therefore, take a relatively short course through the thick ... The avian heart is comparatively large, and the heart rate, cardiac output, and blood pressure are all correspondingly high ...
In a healthy heart, electrical impulses are generated in the sinoatrial (SA) node (sinus node), which is near the junction of ... The His bundle divides into the left and right bundle branches and then into the Purkinje fibers, which conduct the impulse ... This article describes transvenous cardiac pacing. In a healthy heart, electrical impulses are generated in the sinoatrial (SA ... encoded search term (Transvenous Cardiac Pacing) and Transvenous Cardiac Pacing What to Read Next on Medscape. Related ...
Cardiac Evaluation - Free download as Word Doc (.doc), PDF File (.pdf), Text File (.txt) or read online for free. Cardiac ... Impulses to initiate cardiac contractions are conducted along specialized. myocardial fibers. NO NERVES are present in the ... the impulse continues though the bundle of His ( AV bundle). The right and. left bundle branches and the Purkinje network of ... Cardiac muscle has intercalated discs at the junction between cardiac fibers.. These discs contain desmosomes, connectors to ...
B. SA node, AV node, AV bundle, Purkinje fibers. Term. The plateau phase of the cardiac contractile cell action potential is ... Conduction of the cardiac impulse is slowed as it passes through the AV node. This allows time for ... Stevens cardiac output at rest is 5 L/min. When he is exercising strenuously it is 20 L/min. What is Stevens cardiac reserve? ... are the components of the cardiac conduction system listed in the correct order in which they conduct the cardiac impulse? ...
Endothelin-induced conversion of embryonic heart muscle cells into impulse-conducting Purkinje fibers. Proc Natl Acad Sci U S A ... Cardiac-Gated Magnetic Resonance Imaging. Hop−/− and wild-type mice underwent cardiac-gated magnetic resonance imaging (MRI) to ... Synchronized contraction of the atrial and ventricular chambers is essential for normal cardiac function, and the cardiac ... Homeobox Protein Hop Functions in the Adult Cardiac Conduction System. Fraz A. Ismat, Maozhen Zhang, Hyun Kook, Bin Huang, Rong ...
FIGURE 8. Use-dependent block of Na currents in Purkinje fibers. Under control conditions, each of a train of impulses results ... possibly from interference with Ca signaling mech-anisms within cardiac muscle. These anesthetics bind and inhibit cardiac ... Blocking of impulses in a nerve fiber requires that a defined length of nerve become inexcitable (to prevent the impulse from " ... Unmyelinated fibers, lacking the saltatory mechanism, conduct much more slowly than myelinated fibers. Unmyelinated fibers are ...
The mechanisms governing the development of cardiac pacemaking and conduction system are not well understood. In order to ... Endothelin-induced conversion of embryonic heart muscle cells into impulse-conducting Purkinje fibers. Proc Natl Acad Sci USA ... Takebayashi-Suzuki K, Yanagisawa M, Gourdie RG, Kanzawa N, Mikawa T (2000) In vivo induction of cardiac Purkinje fiber ... Terminal diversification of the myocyte lineage generates Purkinje fibers of the cardiac conduction system. Development 121: ...
A cardiac arrhythmia can be identified, such as a tachycardia or fibrillation episode (atrial or ventricular). In responses to ... such as via Purkinje fiber conduction of electrical impulses. Various devices for delivering signals to an electrode near a His ... When the interval ΔtPRE is less than the refractory period of the Purkinje fibers, at least a portion of the Purkinje system ... and the Purkinje fibers, inclusive. Such therapies can improve a cardiac substrate response to a defibrillation shock. In an ...
The goal of this book is to provide an integrated overview of some intriguing problems of cardiac electrophysiology. Topics ... Frequency-Dependent Alterations of Conduction in Purkinje Fibers Charles Antzelevitch, Jose Jalife, Gordon K. Moe ... Recovery of Impulse Propagation in the Bundle Branches of the Human Heart ... The goal of this book is to provide an integrated overview of some intriguing problems of cardiac electrophysiology. Topics ...
  • Sudden cardiac death is the cause of about half of deaths due to cardiovascular disease and about 15% of all deaths globally. (wikipedia.org)
  • Some are barely perceptible, whereas others can be more dramatic and can even lead to sudden cardiac death . (worldebooklibrary.org)