SUMMARY
An action potential is an electrochemical change that is propagated along the length of a nerve cell's axon. It is initiated when a threshold stimulus is applied to the nerve cell. The stimulus causes large numbers of voltage-activated Na⁺ channels to open and Na⁺ to enter the cell, causing a rapid depolarization of the membrane. Inactivation of the voltage-activated Na⁺ channels causes the depolarization phase to stop abruptly. The voltage changes that occur during depolarization trigger the opening of voltage-activated K⁺ channels. The loss of K⁺ from the cell causes the membrane to repolarize. After the action potential is generated, sodium-potassium pumps in the cell membrane return the ions to their original locations.

Activity
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