BIOLOGY 174 Lecture Notes - Lecture 7: Diastole, Tachycardia, Tetany
22 Feb 2017
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Document Summary
Action potentials passing through the conducting system of the heart are strong enough to be detected by electrodes placed on the body surface. Recording the electrical events of the heart: the electrocardiogram. Impulse delays at av node (av node) p wave. Atrial excitation begins action potential (sa node) Ventricular excitation begins in heart apex (bundle branches) Atrial repolarization occurs during the qrs complex but is masked by the larger mass of ventricles. The purkinje fibers of the conducting system of the heart deliver the action potential to the contractile cardiac muscle cells. The action potential is much slower and has a different appearance in the contractile cells compared to the conducting system cells. Depolarization voltage gated na+ channels open na+ enters (+30mv) Long plateau due to entry of calcium. Plateau (slow action potential) creates a long absolute refractory period. Skeletal muscle 2nd stimulus at end of refractory period before twitch is over causes tetany add twitches together.
