Modified cardiac muscle fibers composing the terminal portion of the heart conduction system.

The output neurons of the cerebellar cortex.

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.

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.

Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.

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)

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.

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.

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).

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.

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)

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.

A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.

The superficial GRAY MATTER of the CEREBELLUM. It consists of two main layers, the stratum moleculare and the stratum granulosum.

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.

The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.

The remnants of plant cell walls that are resistant to digestion by the alimentary enzymes of man. It comprises various polysaccharides and lignins.

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.

The hollow, muscular organ that maintains the circulation of the blood.

A surface anesthetic that acts by preventing transmission of impulses along NERVE FIBERS and at NERVE ENDINGS.

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.

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.

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.

Conical muscular projections from the walls of the cardiac ventricles, attached to the cusps of the atrioventricular valves by the chordae tendineae.

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.

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.

Use of electric potential or currents to elicit biological responses.

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.

The hemodynamic and electrophysiological action of the HEART VENTRICLES.

Contractile activity of the MYOCARDIUM.

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.

The ability of a substrate to allow the passage of ELECTRONS.

Mice which carry mutant genes for neurologic defects or abnormalities.

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.

Coronary vasodilator that is an analog of iproveratril (VERAPAMIL) with one more methoxy group on the benzene ring.

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)

Elements of limited time intervals, contributing to particular results or situations.

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.

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.

The innermost layer of the heart, comprised of endothelial cells.

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.

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.

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.

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.

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)

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.

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.

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.

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).

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.

Insulated enclosures in which temperature, humidity, and other environmental conditions can be regulated at levels optimal for growth, hatching, reproduction, or metabolic reactions.

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.

A sulphonylurea hypoglycemic agent with actions and uses similar to those of CHLORPROPAMIDE.

Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.

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.

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.

Pyridines substituted in any position with an amino group. May be hydrogenated, but must retain at least one double bond.

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).

Inorganic compounds that contain barium as an integral part of the molecule.

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.

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.

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.

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)

Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.

A class Ia antiarrhythmic drug that is structurally-related to PROCAINE.

A sulfonylurea hypoglycemic agent that is metabolized in the liver to 1-hydrohexamide.

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.

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.

An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.

The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.

The rate dynamics in chemical or physical systems.

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.

Antiarrhythmic agent pharmacologically similar to LIDOCAINE. It may have some anticonvulsant properties.

A benzoate-cevane found in VERATRUM and Schoenocaulon. It activates SODIUM CHANNELS to stay open longer than normal.

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.

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 .

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.

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.

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.

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.

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.

A calcium channel blocker that is a class IV anti-arrhythmia agent.

Impairment of the ability to perform smoothly coordinated voluntary movements. This condition may affect the limbs, trunk, eyes, pharynx, larynx, and other structures. Ataxia may result from impaired sensory or motor function. Sensory ataxia may result from posterior column injury or PERIPHERAL NERVE DISEASES. Motor ataxia may be associated with CEREBELLAR DISEASES; CEREBRAL CORTEX diseases; THALAMIC DISEASES; BASAL GANGLIA DISEASES; injury to the RED NUCLEUS; and other conditions.