PSIO 485 Study Guide - Midterm Guide: Atrioventricular Node, Cardiovascular Physiology, Purkinje Fibers
26 Sep 2016
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Autorhythmcity means that a signal is generated without any extra input. The heart contracts rhythmically as a result of action potentials that it generates by itself. The pace makers of the heart are the sa node(70-80 action potentials per minute), av node(40-60 action potentials per minute), bundle of his(20-40 action potentials per minute), and the purkinje fibers(20-40 action potentials per minute). The primary pacemaker of the heart is the sa node. This concept explains the mechanism leading to a successful contraction of cardiac cells. More specifically, l-typed ca++ channels located primary on t- tubule will open when signaled by action potentials, letting ca++ into cell. The influx of ca++ will cause sr to release more ca++, increasing cytosolic ca++ to bring about contraction. Without ca++ induced ca++ release, there would not be enough calcium to cause myocyte contraction. No there is no such thing as tetanus. Long refractory periods in the cardiac muscle prevent tetanus from occurring.
