The Hear3 - and relaxation occurs and prevents tetany in...

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The Heart Histology of the Heart Heart Wall o The heart wall consists of the outer epicardium, the middle myocardium, and the inner endocardium. Cardiac Muscle o Cardiac muscle is striated and depends on ATP for energy. It depends on aerobic metabolism. o Cardiac muscle cells are joined by intercalated disks that allow action potentials to be propagated throughout the heart. Electrical Activity of the Heart Action Potentials in Cardiac Muscle o Action potentials in cardiac muscle are prolonged compared with those in skeletal muscle and have a depolarization phase, a plateau phase, and a repolarization phase. o The depolarization is due mainly to opening of the voltage-gated sodium ion channels, and the plateau phase is due to opened voltage-gated calcium ion channels. Repolarization at the end of the plateau phase is due to the opening of potassium ion channels for a brief period. o The prolonged action potential in cardiac muscle ensures that contraction
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Unformatted text preview: and relaxation occurs and prevents tetany in cardiac muscle. o The SA node located in the upper wall of the right atrium is the normal pacemaker of the heart and cells of the SA node have more voltage-gated calcium ion channels than other areas of the heart. Conduction System of the Heart o The conduction system of the heart is made up of specialized cardiac muscle cells. o The SA node produces action potentials that are propagated over the atria to the AV node. o The AV node and atrioventricular bundle conduct action potentials to the ventricles. o The right and left bundle branches conduct action potentials from the atrioventricular bundle through Purkinje fibers to the ventricular muscle. o An ectopic beat results from an action potential that originates in an area of the heart other than the SA node....
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