The resting potential of a neuron is approximately within which range in millivolts?

• A. -60 to -70 mV
• B. -40 to -50 mV
• C. -80 to -90 mV
• D. -20 to -30 mV

Answer: (A)

Resting membrane potential is the voltage difference across the neuron's membrane when it’s not signaling, determined by ion gradients and how permeable the membrane is to those ions. At rest, the membrane is more permeable to potassium than to sodium, so potassium tends to leak out, pulling the inside negative. The sodium–potassium pump helps maintain the ion gradients by moving Na+ out and K+ in, but it doesn’t set the resting potential by itself. The combined effect of these factors places most neurons around -70 mV, with typical values ranging roughly from -60 to -70 mV.

That’s why the other ranges aren’t correct: -80 to -90 mV would be more hyperpolarized than usual and closer to a strict potassium equilibrium potential, while -40 to -50 mV or -20 to -30 mV would reflect a depolarized state, not the resting condition.