In the axon, entry of Na+ during the depolarization phase of the action potentia

Question

In the axon, entry of Na+ during the depolarization phase of the action potential in one region serves to cause entry of Na+ in an adjacent region, ultimately bringing that next segment to threshold potential and causing a new action potential. This occurs down the entire length of an unmyelinated axon or, via saltatory conduction, at the nodes of Ranvier in a myelinated axon. This arrangement can best be described as (a):

(a) Negative feedback loop.

(b) Positive feedback loop.

(c) Feedforward control.

(d) Pathology

(e) None of the above.

Explanation / Answer

The depolarization phase of the action potential can be best described as positive feedback loop.

Positive feedback loop is a process which enhances the changes and makes the system unstable.

Here the entry of the Na+ causes depolarization of the axon and thus makes it unstable. This explains the positive feedback loop.

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