In a resting neuron, the axonal membrane is comparatively more permeable to:

The correct option is K+.

Explanation

The electrical potential difference across the resting neural membrane is known as the resting potential. This potential is established and maintained by the differential permeability of the membrane to specific ions and the activity of ion pumps.

Detailed Analysis:

• In a resting neuron, the axonal membrane acts as a selectively permeable barrier.
• The membrane is comparatively more permeable to Potassium ions (K⁺) and nearly impermeable to Sodium ions (Na⁺).
• This differential permeability is primarily due to the presence of a greater number of open K⁺ leakage channels compared to Na⁺ leakage channels. Consequently, K⁺ ions can diffuse out of the cell down their concentration gradient more easily than Na⁺ ions can enter.
• Additionally, the membrane is impermeable to negatively charged proteins present within the axoplasm.
• The ionic gradients are further maintained by the sodium-potassium pump, which actively transports 3 Na⁺ outwards for every 2 K⁺ into the cell, but the passive permeability characteristic is dominated by K⁺ channels.

Key Takeaway: During the resting state, the neuronal membrane is highly permeable to K⁺ ions and nearly impermeable to Na⁺ ions, which is a critical factor in establishing the negative resting membrane potential.