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Physiology

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Cardiovascular System

Question
6 out of 13
 

The pacemaker potential is due to: (LQ)



A Fast Na+ channel
B Decrease in K+ permeability

C Slow Ca++ channel
D Rapid repolarization

Ans. C Plateau phase of the action potential

Action potential in cardiac muscle: ­

I. Stimulation produces a propagated action potential that is responsible for iniating contraction

II. The initial rapid depolarization and the over-shoot (Phase - 0) are due to opening of voltage gated Na+ channels. Q

III. The initial rapid repolarization (Phase 1) is due to closure of Na+ channels Q.

IV. The subsequent prolonged plateau (phase 2) is due to a slower but prolonged opening of voltage -gated Ca ++ channels Q.

V. Final repolarization (phase -3) to the resting membrane potential (phase -4) is due to closure of the Ca ++ channels and K+ efflux Q

Cardiovascular System Flashcard List

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