Assertion : The resting membrane of the neuron exhibits polarity of charges.\ Reason : The outer su

Question

Assertion : The resting membrane of the neuron exhibits polarity of charges.\ Reason : The outer surface of the axonal membrane possesses a negative charge while its inner surface becomes positively charged.\

Professor PC Thomas Classes · Answer

(c) : When a neuron is not conducting any impulse, i.e., resting, the axonal membrane is comparatively more permeable to potassium ions $\left(\mathrm{K}^{+}\right)$and nearly impermeable to sodium ions $\left(\mathrm{Na}^{+}\right)$. Similarly, the membrane is impermeable to negatively charged proteins present in the axoplasm. Consequently, the axoplasm inside the axon contains high concentration of $\mathrm{K}^{+}$and negatively charged proteins and low concentration of $\mathrm{Na}^{+}$. These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports $3 \mathrm{Na}^{+}$ outwards for $2 \mathrm{~K}^{+}$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 polarised.