Question

The given paragraph describes the resting state of a nerve fiber.
When a neuron is resting, the axonal membrane is comparatively _____P_____ to potassium ions ( $K^{+}$ ) and _____Q_____ to sodium ions ( $N a^{+}$ ). Similarly, the membrane is ______R_____to negatively charged proteins present in the axoplasm. Consequently, the axoplasm inside the axon contains high concentration of _____S_____ and _____T______. P, Q, R, S and T are respectively

• A. More permeable, nearly impermeable, impermeable, $K^{+}$ , proteins
• B. Less permeable, impermeable, impermeable, $K^{+}$ , proteins
• C. More permeable, nearly impermeable, less permeable, $N a^{+}$ , $K^{+}$
• D. Less permeable, highly permeable, impermeable, $K^{+}$ , $C a_{2}^{+}$

Answer 1

Answer: (A)

During the resting state, the axonal membrane is
A. More permeable to $K^{+}$ .
B. Nearly impermeable to $N a^{+}$ .
C. Impermeable to negatively charged proteins present in the axoplasm.
Axoplasm has high concentration of K+ and negatively charged proteins and low concentration of $N a^{+}$ . In contrast, the fluid outside the axon contains a low concentration of $K^{+}$ , a high concentration of $N a^{+,}$ and thus forms a concentration gradient. These ionic gradients across the resting membrane are maintained by the Na–K pump which actively transports $3N a^{+}$ outwards for $2K^{+}$ into the cell.
The outer surface of the axonal membrane is positively charged. The inner surface of the axonal membrane is negatively charged. The axonal membrane is polarised and the potential difference is termed as resting potential.