21 Electrical control of the heart

21 Electrical control of the heart - Biology141...

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4/6/08 1:05 AM Biology141 (Physiology) Page 1 of 4 https://courses.bio.psu.edu/spring2008/biol141/Lecture%2021(2008).htm Biology141 (Physiology) Lecture 21 M. Whim ELECTRICAL CONTROL OF THE HEART [1]. BACKGROUND. heart muscle cells are short, branched and electrically interconnected (gap junctions). so action potentials are conducted from muscle cell to muscle cell. however the cells in the atria and ventricles are separated by connective tissue (the fibrous skeleton ). what is the consequence of the fibrous skeleton for impulse conduction? [2]. THE PACEMAKER POTENTIAL AND IMPULSE CODUCTION. an isolated heart will beat as long as the muscle cells are alive. in a normal heart only one region of the heart shows spontaneous electrical activity: the sinoatrial node (SA node). the SA node acts as a pacemaker that controls the rest of the heart. (a). The SA node and the pacemaker potential. cells of the SA node don’t have a “resting membrane potential”. during diastole the cells slowly depolarize because of sodium influx (the pacemaker potential ). at a critical point of depolarization this results in opening of calcium channels upstroke of action potential. the subsequent downstroke of AP is due to opening of K channels (and efflux of K from the cell).
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21 Electrical control of the heart - Biology141...

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