Repolarization allows for which of the following?

• A. Depolarization
• B. Return of the action potential to the resting threshold
• C. Plateau phase
• D. Hyperpolarization

Answer: (B)

Repolarization is the process by which the membrane potential returns toward the resting level after the peak of the action potential. This happens as potassium exits the cell and sodium channels close, driving the inside of the cell back to a negative value. This resetting is essential because it puts the cell back in a state ready to respond to another stimulus. It describes returning to the resting membrane potential, which is why it best matches the option describing the return to resting potential. The depolarization phase is the preceding rise in voltage, the plateau phase is a prolonged depolarization seen in some cardiac cells, and hyperpolarization is a brief period after repolarization when the membrane becomes more negative than resting.