At the beginning of an action potential, sodium moves
A) slowly into the cell, because electrostatic pressure is offset by diffusion.
B) rapidly into the cell, because both electrostatic pressure and diffusion operate at the same time.
C) slowly out of the cell, because as a positive ion, sodium remains attracted to the relatively negative intracellular environment.
D) rapidly out of the cell, because the sodium-potassium pumps are very active.

Question

Quizplus · Accepted Answer

At the beginning of an action potential, the membrane potential rapidly depolarizes from its resting potential. This depolarization causes voltage-gated sodium channels to open, allowing sodium ions to rapidly move into the cell due to both the electrostatic pressure of the positive ions being attracted to the negative intracellular environment and the diffusion gradient of sodium ions being higher outside of the cell.

At the Beginning of an Action Potential, Sodium Moves