What is the usual resting membrane potential (RMP) of a cell?

What is the usual resting membrane potential (RMP) of a cell?

• A. -60 mV
• B. -90 mV
• C. -70 mV
• D. 0 mV

Answer: (B)

At rest, the membrane potential is mainly set by potassium leak channels. The cell interior is rich in K+ and the membrane is relatively permeable to K+ at rest, so K+ tends to diffuse out, making the inside more negative. The potassium equilibrium potential, given typical intracellular and extracellular K+ concentrations, is about -90 mV. Since other ions (like Na+ and Cl−) contribute less to the resting conductance, the resting membrane potential sits close to that potassium equilibrium value. That’s why many excitable cells have a resting potential around -90 mV. Choosing values like -70 mV or -60 mV would reflect a lesser dominance of K+ conductance or a more depolarized state, and 0 mV would imply no ion gradients influencing the membrane, which isn’t the resting condition.

At rest, the membrane potential is mainly set by potassium leak channels. The cell interior is rich in K+ and the membrane is relatively permeable to K+ at rest, so K+ tends to diffuse out, making the inside more negative. The potassium equilibrium potential, given typical intracellular and extracellular K+ concentrations, is about -90 mV. Since other ions (like Na+ and Cl−) contribute less to the resting conductance, the resting membrane potential sits close to that potassium equilibrium value. That’s why many excitable cells have a resting potential around -90 mV.

Choosing values like -70 mV or -60 mV would reflect a lesser dominance of K+ conductance or a more depolarized state, and 0 mV would imply no ion gradients influencing the membrane, which isn’t the resting condition.