An action potential is regarded as an example of a positive feedback.Which of the following examples below best illustrates the positive feedback aspect of an action potential?
A) The sodium potassium pump consistently moves ions as long as ATP is available, and regardless of membrane potential changes.
B) Potassium permeability is about 25 times greater than sodium ions.
C) Voltage gated potassium ion channels open slowly and remain open long enough to cause hyperpolarization.
D) A threshold stimulus will cause the opening of voltage gated sodium ion channels that will cause further depolarizing stimulus. This stimulus will open still more voltage gated sodium ion channels.

Question

Quizplus · Accepted Answer

Positive feedback is a process where a stimulus has a self-amplifying effect leading to an increase in the output. In an action potential, the opening of voltage-gated sodium ion channels by a threshold stimulus results in depolarization, which opens more voltage-gated sodium ion channels. This leads to a self-amplifying effect, resulting in the generation of a large and rapid action potential, which is an example of positive feedback. A, B, and C do not illustrate positive feedback. A describes a mechanism that operates continuously and regardless of changes in membrane potential; B describes a difference in ion permeability and not feedback; C describes the opening of voltage-gated potassium ion channels that repolarize the membrane potential, and hence, it does not lead to a self-amplifying effect.

An Action Potential Is Regarded as an Example of a Positive