When a neuron is in resting state i.e. not conducting any impulse, the axonal membrane is

Options

A. Comparatively more permeable to `Na^(+)` ions and nearly impermeable to `K^(+)` ions
B. Equally permeable to both `Na^(+)` and `K^(+)` ions
C. Impermeable to both `Na^(+)` and `K^(+)` ions
D. Comparatively more permeable to `K^(+)` ions and nearly impermeable to `Na^(+)` ions

Answer

**Step-by-Step Solution:**

1. **Understanding Resting State of Neuron:**
- A neuron in its resting state is not conducting any electrical impulse. This state is characterized by a specific voltage difference across the axonal membrane known as the resting membrane potential.

2. **Resting Membrane Potential:**
- The resting membrane potential is the voltage difference across the cell membrane when the neuron is at rest. It typically ranges from -70 to -90 mV, indicating that the inside of the neuron is negatively charged relative to the outside.

3. **Ion Distribution:**
- In the resting state, there is a distinct distribution of ions:
- The exterior of the neuron has a higher concentration of sodium ions (Na⁺) and is positively charged.
- The interior of the neuron has a higher concentration of potassium ions (K⁺) and is negatively charged.

4. **Role of Sodium-Potassium Pump:**
- The sodium-potassium pump (Na⁺/K⁺ ATPase) actively transports 3 sodium ions out of the neuron and 2 potassium ions into the neuron, maintaining the concentration gradient essential for resting potential.

5. **Permeability of the Membrane:**
- The axonal membrane contains protein channels known as leakage channels. These channels allow ions to move across the membrane.
- In resting state, the membrane is more permeable to potassium ions (K⁺) than to sodium ions (Na⁺). Specifically, it allows more K⁺ to leak out compared to Na⁺ leaking in.

6. **Conclusion:**
- Therefore, when a neuron is in its resting state, the axonal membrane is comparatively more permeable to potassium ions and nearly impermeable to sodium ions.

**Final Answer:**
- The axonal membrane is comparatively more permeable to potassium ions and nearly impermeable to sodium ions.

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