The resting membrane potential of a typical neuron lies closest to the equilibrium potential of which ion, reflecting the membrane's high resting permeability to it?

• A Sodium (Na+)
• B Calcium (Ca2+)
• C Potassium (K+) ✓
• D Chloride (Cl−)

Explanation

At rest the membrane is most permeable to K+ (through leak channels), so the resting membrane potential (≈ −70 mV) lies close to the K+ equilibrium potential (≈ −90 mV). The Na+/K+-ATPase maintains the ionic gradients but contributes only a small electrogenic component directly.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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