Question

In resting nerve what is true

• A. 3N$a^{+}$ are pumped in and 2 $K^{+}$ pumped out
• B. 3N$a^{+}$ are pumped out for every 2$K^{+}$ pumped in
• C. There is no Na-K pump
• D. Na-K pump stops working

Answer 1

Answer: (B)

3N$a^{+}$ are pumped out for every 2$K^{+}$ pumped in

B. $3N{a}^{+}$ are pumped out for every $2K^{+}$ pumped in

Reason: In resting nerve fibre (a nerve fibre that is not conducting an impulse), the axoplasm inside the axon contains a high concentration of $K^{+}$ and negatively charged proteins and a low concentration of $N{a}^{+}$. In contrast, the fluid outside the axon contains a low concentration of $K^{+}$ and a high concentration of $3N{a}^{+}$. These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports $3N{a}^{+}$ outwards and $2K^{+}$ inwards (into the cell). As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged, and therefore, is polarized.