BIOL 222L Lecture Notes - Lecture 5: Skeletal Muscle, Pr Interval, Qt Interval

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Action potentials in contractile cells [old figure] single cell. Fall 2015: resting membrane potential cardiac muscle 90mv. Depolarization same as in skeletal muscle, voltage-regulated sodium channels open at threshold; rapid depolarization. Plateau at +30mv the sodium channels close and voltage-regulated calcium channels open. These channels remain open for 175msec holding membrane potential near 0mv this is different from skeletal muscle action potentials. Repolarization calcium channels close and potassium voltage-regulated channels open. P wave depolarization of the atria (0. 06-0. 11 s) Qrs wave depolarization of the ventricles; repolarization of the atria (< 0. 12 s) T wave repolarization of the ventricles (0. 16 s) Pr segment atria depolarized (plateau of the action potentials) and ventricles resting (0. 08 s) Pr interval time it takes the action potential to travel through the atria and av node, av bundle, bundle branches and purkinje fibers (no net current flow) (0. 12-0. 2 s)

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