Lecture 7 – Cardiovascular Physiology I

Allow contractile force to be transmitted from cell

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Allow contractile force to be transmitted from cell to cell Gap Junction Allow for electrical activity to pass rapidly from cell to cell Heart Beat Coordination This is necessary for unidirectional flow and have flow timed correctly so that the  ventricle and atria do NOT contract a the same time 1% of cardiac cells do not contract they constitute the conducting system of the heart electrical contact through gap junctions allow depolarization to spread very rapidly  SA node Initiates the heartbeat Conduction system is designed to spread a wave of depolarization across the  myocardium in an ordered way The atria have to contract first, and after a brief delay the ventricles contract Depolarization of the plasma membrane Autorhythmic cells in the right atrium, they fire an AP every so often like clockwork Spreads through a specialized conduction of autorhythmic cells to the AV node From the AV node the depolarization spreads down through the bundle of purkinje cells  which goes down the intraventricular septum Spreads down this set of conducting branches very rapidly and arrives at the apex of the  heart, then spreads up the sides Fibrous tissue prevents signal transmission from the ventricles to the atria directly If you had AP generation in the apex of the ventricles, there would be backwards  pressure buildup The ventricles contract from the bottom up 10 th  of a second delay allows for the ventricles to fill before they contract conduction from the AV node is VERY rapid reaches the apex of the heart almost instantly and the wave of depolarization spreads  instantly purkinje fibers tell the papillary muscles when to contract they contract against the pressure so that they don’t blow back through the sinoatrial  valves they contract before the rest of the atria to prevent backflow
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