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

Answer 1

The correct option is D A neuron is polarised only when the outer surface of axonal membrane possesses a negative charge and inner surface is positively charged

In a resting neuron the resting potential is -70 mV, this means that the inside of the neuron is negatively charged. The neuronal membrane is more permeable to K+ ions and less permeable to Na+ ions. The $Na$ - $K$ pump tries to balance the negative charge by pumping 3 $N{a}^{+}$ ions inside and 2 $K^{+}$ ions outside.When neurons receive a signal, an action potential is generated and depolarization of membrane occurs. Resting membrane potential is pushed towards 0 mV. When depolarization reaches -55 mV the action potential is fired by the neuron. This means the outer surface still remains positively charged.

Thus the correct answer is option C.