Question

During the conduction of nerve impulse the repolarization occurs with the

• A. Influx of $K^{+}$ ions
• B. Efflux of $K^{+}$ ions
• C. Efflux of N$a^{+}$ ions
• D. Influx of N$a^{+}$

Answer 1

The correct option is B Efflux of $K^{+}$ ions

The generation and conduction of nerve impulse are characterized by the following changes across the axon membrane:

1. Polarization: This occurs at the resting stage when the Na${}^{+}$ are transported out of the intracellular compartment to the extracellular fluid.
2. Depolarization: This occurs due to the influx of the Na${}^{+}$ into the intracellular fluid which makes the interior of the membrane positive.
3. Repolarization: This occurs due to the efflux of the K${}^{+}$ ions to the extracellular fluid due to the voltage-gated K-channels.
4. Hyper-polarization: The excessive efflux of the K${}^{+}$ causes a more negative membrane potential which is restored to the normal polarization state by the efflux of the Na${}^{+}$ by the activity of the Na${}^{+}$-K${}^{+}$ pumps.

Hence, the correct answer is 'Efflux of K${}^{+}$ ions'