Which ion plays a key role in the repolarization phase of the action potential?

Which ion plays a key role in the repolarization phase of the action potential?

• A. Na+
• B. K+
• C. Ca2+
• D. Cl-

Answer: (B)

In the context of the action potential in neurons, the repolarization phase is primarily driven by the movement of potassium ions (K+) across the cell membrane. During the depolarization phase, sodium ions (Na+) flood into the cell, causing the membrane potential to become more positive. However, once the peak of the action potential is reached, the voltage-gated sodium channels close, and voltage-gated potassium channels open. This opening of potassium channels allows K+ to flow out of the cell, which causes the membrane potential to become more negative again, moving it back toward the resting membrane potential. This outflow of potassium is essential for repolarization because it counteracts the influx of sodium that occurred during depolarization. The restoration of the membrane potential is crucial for the neuron to return to its resting state, allowing it to prepare for the possibility of another action potential. While sodium ions are important for depolarization, calcium ions (Ca2+) play roles in various signaling processes within the cell but are not directly involved in repolarization. Chloride ions (Cl-) also have functions in neuronal signaling, but they do not specifically drive the repolarization phase of the action potential as potassium ions do. Thus, the involvement of

In the context of the action potential in neurons, the repolarization phase is primarily driven by the movement of potassium ions (K+) across the cell membrane. During the depolarization phase, sodium ions (Na+) flood into the cell, causing the membrane potential to become more positive. However, once the peak of the action potential is reached, the voltage-gated sodium channels close, and voltage-gated potassium channels open.

This opening of potassium channels allows K+ to flow out of the cell, which causes the membrane potential to become more negative again, moving it back toward the resting membrane potential. This outflow of potassium is essential for repolarization because it counteracts the influx of sodium that occurred during depolarization. The restoration of the membrane potential is crucial for the neuron to return to its resting state, allowing it to prepare for the possibility of another action potential.

While sodium ions are important for depolarization, calcium ions (Ca2+) play roles in various signaling processes within the cell but are not directly involved in repolarization. Chloride ions (Cl-) also have functions in neuronal signaling, but they do not specifically drive the repolarization phase of the action potential as potassium ions do. Thus, the involvement of