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Physiology

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Basic Concepts

Question
84 out of 95
 

amplitude of action potential can be increased maximally by



A decreased absolute refractory period

B increased no. of open Na+ channel

C increased no. of open K+ channel

D increased frequency of opening of Na+ channel

Ans. B increased no. of open Na+ channel

a. Na+ is critical for the action potential in nerve cells. Action potentials are repeatedly initiated as the extracellular concentration of Na+ is modified.

b. As the concentration of sodium in the extracellular solution is reduced, the action potentials become smaller. Same is observed when we block sodium channels.

c. K+ channels are responsible for repolarisation, so they will rather decrease the amplitude of AP, infact if only sodium channels were there in open state not K+, amplitude would reach close to equilibrium potential of sodium i.e. +60 mV.

d. The absolute refractory period is a period of time after the initiation of one action potential when it is impossible to initiate a second action potential no matter how much the cell is depolarized. So, it is not a major factor for amplitude since no AP would occur here and if we shorten it and get 2nd AP , its amplitude is always less than the first one.

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