The resting membrane potential of a ventricular myocyte is approximately −90 mV. This potential is primarily maintained by which ion's equilibrium?

• A Sodium
• B Calcium
• C Chloride
• D Potassium ✓

Explanation

The resting membrane potential of ventricular myocytes (−85 to −95 mV) is primarily determined by the high permeability to K+ at rest through inward rectifier K+ channels (IK1). The equilibrium potential for K+ is approximately −94 mV, which closely approximates the resting membrane potential. The Na+/K+ ATPase pump also contributes by maintaining ionic gradients.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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