In the axon entry of Na during the depolarization phase of t

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.

Solution

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.