An action potential begins when
A) sodium channels open.
B) potassium channels open.
C) both sodium and potassium channels open.
D) sodium channels close.
E) both sodium and potassium channels close.

Question

Quizplus · Accepted Answer

An action potential begins when voltage-gated sodium channels open in response to depolarization, allowing sodium ions to rush into the cell and causing a rapid increase in membrane potential. This depolarization phase is followed by the opening of voltage-gated potassium channels, which allow potassium ions to exit the cell and restore the resting membrane potential. However, the initial trigger for the action potential is the opening of sodium channels. Therefore, choice A is the correct answer.

An Action Potential Begins When