Answer the following questions: a) Subthreshold potentials decay in amplitude ov

Question

Answer the following questions:

a) Subthreshold potentials decay in amplitude over distance, but action potentials do not. Explain.

b) What is the effect of increasing the density of Na+ channels on the action potential threshold and action potential peak in the squid giant axon?

c) The recovery or repolarizing phase of the action potential is due to the action of the Na+-K+ ATPase, which essentially extrudes the Na+ that entered, and returns the K+ that left, the cell during the rising or spike phase. Explain whether you agree or disagree with this statement.

Explanation / Answer

a) The amplitude of subthreshold potential is already very small. Such small voltage current will decay in a very short duration of time. On the other hand, the amplitude of action potential is large. It increases from -60mV of resting stage to +40mV for creating an action potential.

b) Action potential threshold, follows all or none law. So, if you increase the density of Na+ channels, then also action potential will reach only when the membrane depolarisation has reached +30mV. Although the time taken so the same may be reduced.

c) Repolarisation results after movement of positively charged potassium ions out of the cell. It has nothing to do with sodium channels.

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