Which term describes the restoration of the resting membrane potential after depolarization, with potassium leaving the cell?

• A. Depolarization
• B. Repolarization
• C. Hyperpolarization
• D. Resting potential

Answer: (B)

Repolarization is the restoration of the resting membrane potential after depolarization, driven by potassium leaving the cell. As the action potential peaks, voltage-gated potassium channels open and K+ ions exit, moving the membrane potential back toward the negative resting value. This outward K+ efflux counters the prior positive shift from Na+ influx, reestablishing the negative resting potential. Sometimes the membrane becomes briefly more negative than the resting level (hyperpolarization) before returning to baseline, but the process described—returning to resting potential via potassium efflux—is repolarization.