KIN110 Lecture Notes - Lecture 4: Sinus Rhythm, Tetanic Contraction, Atrioventricular Node
14 Sep 2016
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Document Summary
Gap junctions electrically couple all the cardiac muscle cells in your heart this allows our heart to work as a whole unit and one big pump. Heart has within it it"s own self-excitable cells (automaticity) Has a long refractory period (250 ms), opposite of skeletal muscle (1-2 ms) Long refractory period for cardiac cells is essential to ensure that the cardiac muscles work over your lifetime. Heart contraction is stimulated by action potentials and the action potential is prolonged in the cells. All-or-none law applies to the entire organ (heart) rather than individual cells. The heart doesn"t need any external neural input to work on it"s own - refractory period (250 ms) takes almost as long as the muscle contraction of the heart itself. The long refractory period is to ensure that tetanic contraction does not occur. By the time the refractory period is over the heart muscles are starting to relax as well.
