Contraction of Myocardium - Edubirdie

University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2019
Views:

329

Pages:

2
Author:

mareangely2

Contraction of Myocardium • Myocytes have stable resting potential of -90 mV • Depolarization (very brief) – stimulus opens voltage regulated Na+ channels and allows Na+ to rush in which rapidly depolarizes the membrane – action potential peaks at +30 mV – Na+ channels close again quickly • Plateau of 200 to 250 msec, sustains contraction – slow Ca+2 channels open, Ca+2 binds to Ca+2 channels on sarcoplasmic reticulum which releases Ca+2 into cytoplasm and results in muscle contraction • Repolarization - Ca+2 channels close, K+ channels open, rapid K+ outflow returns cell to resting potential Myocardial Contraction and Action Potential 1) Voltage gated Na+ channels open 2) Rapid depolarization due to Na+ inflow 3) Na+ channels close 4) K+ channels and slow Ca+2 channels open. K+ flows out restoring membrane polarity, but Ca+2 flowing in prolongs membrane depolarization 5) Ca+2 channels close and Ca+2 is pumped out K+ channels still open and re-polarizes as K+ flows out

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