Question

Which of the following statements is wrong regarding conduction of nerve impulse?

• A. In a resting neuron, the axonal membrane is more permeable to $K^{+}$ ions and nearly impermeable to $N{a}^{+}ions$.
• B. Fluid outside the axon has a high concentration of $N{a}^{+}$ and low concentration of $K^{+}$ in a resting neuron.
• C. Ionic gradients are maintained by Na - K pumps across the resting membrane which transport $3N{a}^{+}$ ions outwards for $2K^{+}$ ions into the cell.
• D. Resting potential is the electrical potential difference across the resting membrane.
• E. A neuron is polarised only when the outer surface of the axonal membrane possess a negative charge and its inner surface is positively charged.

Answer 1

The correct option is E A neuron is polarised only when the outer surface of the axonal membrane possess a negative charge and its inner surface is positively charged.

In a resting neuron, the axonal membrane is more permeable to $K^{+}$ ions and nearly impermeable to $N{a}^{+}ions$. Hence, the fluid outside the axon has a high concentration of $N{a}^{+}$ and low concentration of $K^{+}$ and thus, the outer surface of the axonal membrane possesses a positive charge. This gradient in ions is maintained by Na - K pumps which actively transport $3N{a}^{+}$ ions outwards for $2K^{+}$ ions into the cell.
As an action potential arrives, the outer surface of the axonal membrane becomes positively charged, while its inner surface becomes negatively charged and therefore, gets polarised.