What is the normal resting membrane potential of most cells?

What is the normal resting membrane potential of most cells?

• A. -60 mV
• B. -70 mV
• C. -80 mV
• D. -90 mV

Answer: (D)

Resting membrane potential is set by the balance between ion gradients and how permeable the membrane is to those ions. At rest, the membrane is most permeable to potassium, which leaks out of the cell. This outward flow makes the inside negative. The potassium equilibrium potential, given the typical intracellular and extracellular potassium concentrations, is about -90 mV. Because the resting membrane is dominated by K+ leak, the resting potential sits close to that value. In many cells, there is some Na+ leak as well, which brings the value a bit toward -70 mV, but the strongest influence remains potassium, so -90 mV is a common reference point for the resting potential.

Resting membrane potential is set by the balance between ion gradients and how permeable the membrane is to those ions. At rest, the membrane is most permeable to potassium, which leaks out of the cell. This outward flow makes the inside negative. The potassium equilibrium potential, given the typical intracellular and extracellular potassium concentrations, is about -90 mV. Because the resting membrane is dominated by K+ leak, the resting potential sits close to that value. In many cells, there is some Na+ leak as well, which brings the value a bit toward -70 mV, but the strongest influence remains potassium, so -90 mV is a common reference point for the resting potential.