13609 Cardiac Muscle Outline

13609 Cardiac Muscle Outline - relaxation stop action...

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MUSCLE Cardiac Muscle Tissue and cellular structure: branched cells with intercalated disks (gap junctions and desmosomes) sarcomeres, SR and T-tubules similar to but less extensive vs skeletal muscle actin, myosin, Tn's, nebulin and titin similar to skeletal muscle Contractile mechanism contract: shorten sarcomeres and reduce heart volume, pumping relax: stretched out as heart refills Electrical activity action potential and ion channels: two types of K channels (depolarization opens and depolarization closes) Na channel (V-dependence like skeletal muscle) Ca channel (V-dependent, also regulated by epinephrine) extended action potential with long refractory period (assures rhythmicity) cell-to-cell propagation of action potential through gap junctions excitation-contraction coupling Ca entry through Ca channels in plasma membrane T-tubules and Ca channels/DHP receptors that also elicit Ca entry SR and ryanondine receptors (RyR-Ca channels), Ca release (regulate contraction - Tn) Ca uptake by SR Ca-ATPase (SERCA): Ca bound to calreticulin and calsequestrin
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Unformatted text preview: relaxation stop action potential Ca channels in plasma membrane and in SR close Ca transported out of the cell by SERCA and PMCA (plasma membrane CaATPase) Ca no longer bound to Tn, actin-myosin relax regulation of electrical and contractile activity sympathetic - norepinephrine, beta receptors, cAMP/PKA cAMP/PKA regulates: Ca channels, increase contractility (directly and CICR of RyR) shortens action potential phospholamban, which regulates SERCA, speeds relaxation and increases Ca uptake and subsequent release of Ca clinical: digitalis inhibits Na/K-ATPase and increases contractility Pacemakers regulate action potential frequency SA and AV nodes action potential and ion channels: K channels, "funny channels" and Ca channels gradual depolarization (unsteady baseline) to threshold to generate action potential regulation: sympathetic - speeds gradual depolarization parasympathetic - slows gradual depolarization...
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