Question

In the nerve cells, the reversal of the resting potential is known as depolarization. This occurs due to

• A. Influx of $N{a}^{+}$
• B. Influx of $C{a}^{2+}$ and Cl
• C. Influx of $K^{+}$
• D. Influx of $M{g}^{+}$

Answer 1

The correct option is A Influx of $N{a}^{+}$

When an axon receives the stimulus, a wave of depolarization passes through it reversing the membrane potential with the inner surface becoming positive and outer surface electronegative due to
(i) membrane becoming 10 times more permeable to $N{a}^{+}$ than $K^{+}$ from extracellular fluid to the neutron interior.
(ii) Stoppage of $N{a}^{+}{K}^{+}$ pump.
Depolarization is caused by influx of cations, e.g., $N{a}^{+}$ through $N{a}^{+}$ channels, or $C{a}^{2+}$ through $C{a}^{2+}$ channels. These channels, also known as voltage-dependent ion channels, open when an action potential begins, or at the threshold potential.