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Physiology

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Cardiovascular System

Question
5 out of 13
 

SA node is the pacemaker of heart because:



A It generates impulses at a faster rate

B It generates impulse spontaneously

C It is richly supplied by sympathetic nerve

D lt is poorly supplied by parasympathetic nerve

Ans. B Decrease in K+ permeability

Pacemaker potentials or Pre potentials: ­

I. "Rhythmically-discharging cells have a membrane potential that, after each impulse, declines to the firing level. Thus, this pre potential or pacemaker potential triggers the next impulse. Q

II. At the peak of each impulse, IK begins and brings about repolarization IKthan declines, and as K+efflux decreases (ie: in r permeability), the membrane begins to depolarize, forming the first part of the pre potential. Ca++ channels then open two types - T - channels (transient channels) and L-channels (L = long-lasting). The calcium current (lca) due to opening of T ­channels completes the prepotential, and lca due to opening of L-channels produces the impulse.

Cardiovascular System Flashcard List

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