Lecture 3 - NPB113 Electrophysiology 3-1 Activation of the...

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1 January 7, 2010 NPB113 Electrophysiology 3-1 Activation of the Heart Topics Parameters that affect conduction through cardiac tissue Spread of Activation through the heart Refractory Properties of Cardiac Tissue and Conduction Tissue Effective Refractory Period (ERP) & Distinction from a Cell’s Absolute Refractory Period Relative Refractory Period (RRP) of a Cardiac Cell and Tissue Channel State of the Inward Current Channels and a Cells ARP and RRP . Affect of ARP and RRP of Cells on ERP and RRP of a Tissue Intracellular Chemical Environments and Cell to Cell Conductivity
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2 January 7, 2010 NPB113 Electrophysiology 3-2 Parameters that Govern Cell to Cell Spread of Activation 1. Rate of Rise and Amplitude of AP Faster Rate of Rise and Higher the Amp litude faster electrical coupling between cells and more rapid depolarization of unactivated cell to threshold and AP generation. 2. Number and Conductivity of low resistance junctions ( tight junctions within the Intercalated Disks ) between adjacent cell # and conductivity of the low resistance junction determines electrical coupling among adjacent cells & rate of spread of activation. 3. Geometric Relationship among Adjacent Cells – surface area for contact and cell to cell spread of activation. II orientation , where cells oriented side to side, facilitates cell to cell spread of activation orientation , where the end of one cell abuts the lateral surface of another cell, less effective electrical coupling between cells. 4. Refractory State of Inward Current Channels and Cardiac Tissue the fewer the number of inward current channels in their rested state , the slower the inward current flow reduced rate of rise and amplitude AP slower cell to cell spread of activation
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January 7, 2010 NPB113 Electrophysiology 3-3 Structure of SA Node and Sino-Atrial Conduction SA Node – 20mm x 5mm x 1mm (humans) Pacemaker cells center of node Surrounded by Transitional Cells (electrophysiological characteristics both pacemaker cells and atrial muscle cells) Atrial muscle cells surround node. Few low resistant junctions among cells within node. Sino – Atrial Conduction Time slow , 80 – 100 msec. (0.05 M/sec) Most conduction delay between T & At cells. Weak Electrical Coupling + apposition of cell membranes. P
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This note was uploaded on 04/09/2010 for the course NPB npb 113 taught by Professor Goldberg during the Spring '10 term at UC Davis.

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Lecture 3 - NPB113 Electrophysiology 3-1 Activation of the...

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