BIOM3010 Lecture Notes - Lecture 2: Cardiac Muscle, Depolarization, Action Potential

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4 Aug 2018
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Lecture 2 - electrical activity of the heart. 1% autorhythmic cells pacemaker cells: non-contractile, generate action potentials. Cardiac cells contract simultaneously due to gap junctions. Conduction system of the heart and spread of cardiac excitation: Phase 1: rapid depolarisation by brief influx of na+ via voltage- sensitive channels. Phase 2: plateau due to decrease in k+ out and entry of ca2+ Phase 3: rapid repolarisation due to rapid return of k+ permeability and a closure of ca2+ channels. Phase 4: resting return to slow na+ (leak in) and k channels (leak out) and atpase pump dominance. The overall spread of electrical activity the heart can be monitored by body surface electrodes and recorded as. Electrodes record magnitude and direction of electrical activity. Normal ecg has three distinctive waves: p wave, ors complex, t wave. Electrical status of heart associated with ecg waveform: Normal rates: sa node: 70-80, av node: 40-60, bundle of his and purkinje fibers: 20-40.

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