What is the term for membrane potential becoming more negative than resting during an action potential overshoot?

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

Answer: (A)

Hyperpolarization is the phase after the peak of an action potential where the membrane potential becomes more negative than the resting value. This happens because potassium channels remain open longer, allowing extra K+ to leave the cell and drive the interior to a more negative level. The membrane potential may then dip briefly below the resting potential, an interval often called the afterhyperpolarization, which helps reset excitability and contributes to the refractory period. By contrast, depolarization is when the membrane potential becomes less negative, repolarization is the return toward resting, and resting potential is the baseline value. So the term for becoming more negative than resting is hyperpolarization.