Question

The depolarization of the axonal membrane is due to:

• A. Influx of sodium ions
• B. Efflux of sodium ions
• C. Influx of potassium ions
• D. Efflux of the potassium ions

Answer 1

The correct option is A Influx of sodium ions

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.

When stimulus is applied at the the neuron, it results in opening of $N{a}^{+}$ channels and causes rapid movement of $N{a}^{+}$ into the cell leading 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. This is depolarization of the neuron and neuron is called a depolarized neuron.