During an action potential, the membrane potential returning toward the resting value as potassium exits the cell is called

During an action potential, the membrane potential returning toward the resting value as potassium exits the cell is called

• A. Depolarization
• B. Repolarization
• C. Hyperpolarization
• D. Plateau phase

Answer: (B)

Repolarization is the phase where the membrane potential moves back toward the resting value as potassium leaves the cell. After the peak of the action potential, voltage-gated potassium channels open and K+ exits the neuron, pulling the membrane potential from a positive level back toward the resting potential. This outward positive current counteracts the earlier inward Na+ current that caused depolarization. This step distinguishes itself from depolarization (the initial rise in membrane potential due to Na+ influx) and from hyperpolarization (when the membrane becomes more negative than resting), and from the plateau phase (a prolonged depolarization seen in cardiac cells due to Ca2+ influx).

Repolarization is the phase where the membrane potential moves back toward the resting value as potassium leaves the cell. After the peak of the action potential, voltage-gated potassium channels open and K+ exits the neuron, pulling the membrane potential from a positive level back toward the resting potential. This outward positive current counteracts the earlier inward Na+ current that caused depolarization. This step distinguishes itself from depolarization (the initial rise in membrane potential due to Na+ influx) and from hyperpolarization (when the membrane becomes more negative than resting), and from the plateau phase (a prolonged depolarization seen in cardiac cells due to Ca2+ influx).