HLSC 3P90 Lecture Notes - Lecture 2: Muscarinic Acetylcholine Receptor, Bainbridge Reflex, Nucleus Ambiguus
13 Sep 2017
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Document Summary
Impulse transmission is raid (150x greater than av node) Innervate few cardiac myocytes as depolarization is spread throughout the myocyte by gap junction. Na: na/k atp pump restores balance of na and k, 3 na out 2k in. Phase 0: atp makes membrane potential less (-, na channel open - follows concentration and electrostatic gradient to inside the cell, makes transmembrane potential less negative. 70 = threshold potential: fast na channels open, overshoot (threshold reaches +20-30mv, fast na channels fast to close as well. Phase 1: efflux of k through transiently activated potassium channels is a result of, electrostatic gradient, concentration gradient, brief period of early repolarization. Phase 3: rapid repolarization, efflux of k exceeds influx of ca. Action potential of pacemaker cells: slow response, pacemaker cells, self-initiating depolarization, automaticity - spontaneous depolarization, maximum negative voltage = -60mv, cases fast na channels to be inactive. Ion channels work to restore ion concentrations back to rest.
