Question

Which of the following is correct about generation and conduction of nerve impulse?

• A. The electrical potential difference across the resting plasma membrane is called the action potential
• B. At resting phase, the axonal membrane is comparatively more permeable to potassium ions $\left(K^{+}\right)$ and nearly impermeable to sodium ions $\left(N{a}^{+}\right)$
• C. The ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports $2N{a}^{+}$ outwards for $3K^{+}$ into the cell
• D. Depolarization is due to rapid influx of potassium ions

Answer 1

The correct option is B At resting phase, the axonal membrane is comparatively more permeable to potassium ions $\left(K^{+}\right)$ and nearly impermeable to sodium ions $\left(N{a}^{+}\right)$

When a neuron is at a resting phase, it is not conducting any impulse. The axonal membrane is comparatively more permeable to potassium ions $\left(K^{+}\right)$ and impermeable to sodium ions $\left(N{a}^{+}\right)$ and to negatively charged proteins present in the axoplasm. The electrical potential difference across the resting plasma membrane is called the resting potential. The ionic concentration difference across the resting membrane are maintained by the active transport of $N{a}^{+}$ and $K^{+}$ ions by the sodium-potassium pump which transports $3N{a}^{+}$ ions outside the cell and $2K^{+}$ ions into the cell.

Rapid influx of $N{a}^{+}$ leads to the change of polarity at the site of membrane i.e., the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged and hence it is called depolarised.