Ace the CVS Pharmacy Exam 2025 - Your Prescription for Success!

The resting membrane potential (RMP) is primarily influenced by the movement of potassium ions (K+) across the neuronal membrane. At rest, the neuron is more permeable to potassium than to other ions, which means that potassium ions tend to move out of the cell. This efflux of positively charged potassium ions results in a negative charge inside the neuron compared to the outside, establishing a negative resting potential, typically around -70 mV.

The RMP is also affected by the sodium-potassium pump, which actively transports sodium (Na+) out of the cell while bringing potassium into the cell, maintaining the concentration gradients essential for RMP. However, the key ion that directly contributes to the electrical charge across the membrane at rest is potassium. The permeability of the membrane to potassium is significantly higher than it is for sodium or any other ion, making potassium the primary determinant of the resting membrane potential.