Question

explain how an action potential is generated in a nerve cell. be sure to incorporate and explain the following terms in to your response: action potential, repolarization, threshold, resting potential, depolarization

Answer 1

Action Potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls.

Action potential occurs in several types of cells like Nerve cells, muscle cells, endocrine cells etc. These cells have plasma membranes capable of producing action potential. They contains special type of voltage-gated ion channels.

Nerve signals are transmitted by action potential. Each action potential begins with a sudden change from normal resting membrane potential (-90mV) to positive potential (+30mV). Then ends rapidly.

stages of action potential:

Resting Membrane potential Before action potential begins cell is in resting stage. The membrane is "polarized " at this stage ; because -90mV resting membrane potential is present.

Depolarization When an impulse generated, all sodium channels are open and allow inward flow of Na⁺ ,which changes the electrochemical gradient. This in turn produces a further rise in membrane potential which is called Threshold value. This causes more channels to open. The potential rising rapidly in the positive direction. This is called Depolarization.

Few millisecond after depolarization the sodium channels begins to close and potassium channels open. Then rapid diffusion of K⁺ to the outside of the cell reestablish the normal resting membrane potential. This is called Repolarization.