What is hyperpolarization?

• A. Membrane becomes more negative than resting
• B. Membrane becomes more positive
• C. Membrane returns to resting potential
• D. Membrane remains depolarized

Answer: (A)

Hyperpolarization is when the neuron's membrane potential becomes more negative than its resting value. After an action potential, voltage-gated potassium channels stay open longer, letting extra K+ exit the cell. That outward flow drives the interior further negative than during rest, creating a brief hyperpolarized state. This makes it harder for the neuron to fire again right away, contributing to the refractory period. The resting potential is typically around -70 mV, and hyperpolarization may push it a bit more negative, like -75 to -80 mV, depending on the neuron. This is different from depolarization (becoming more positive), repolarization (returning to resting), or a sustained depolarized state (remaining above resting for longer).