Lect21 - Feb 3 - Cardio IV

Lect21 - Feb 3 - Cardio IV - Duration of the RRP is long...

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January 20, 2011 15 CV 15 Concepts of Effective and Relative Refractory Periods for Cardiac Tissues Refractory Properties of Cardiac Tissue ERP for Tissue – Tissue behaves as if its cells are inexcitable . No Spread of Activation through tissue. Therefore conduction block. RRP for Tissue – Tissue is excitable . Spread of Activation through tissue . However, conduction velocity slowed & conduction time prolonged because time course for cell to cell spread of activation is prolonged. During ERP of a tissue, an AP may or may not be generated in cells within the tissue, but the APs are incapable of generating an AP in the adjacent tissue . Therefore, the tissue behaves as if it is inexcitable, refractory . Question: If a tissue segment is Effectively Refractory, can you conclude that all the cells in the tissue are in their ARP? ERP - is the tissue excitable? Duration of the RRP is long (about 15msec). The earlier in the RRP the next stimulus arrives, the slower the rate of rise of the AP and the lower the amplitude of the AP. Due to the fact that fewer INa channels are recovered back to resting. AP generation in a single cell or group of cells doe not help the heart act as a pump. .. all cells must depolarize together. AV node - cells in RRP.
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This note was uploaded on 08/21/2011 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Winter '08 term at UC Davis.

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Lect21 - Feb 3 - Cardio IV - Duration of the RRP is long...

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