The resting membrane potential of a cardiac cell is approximately how many millivolts?

The resting membrane potential of a cardiac cell is approximately how many millivolts?

• A. -70 mV
• B. -60 mV
• C. -90 mV
• D. -50 mV

Answer: (C)

The resting membrane potential in cardiac myocytes is set mainly by potassium conductance, so the membrane sits close to the potassium equilibrium potential, which is about -90 mV. The Na+/K+ pump maintains the ion gradients that make this possible, but at rest the membrane is most permeable to K+, driving the potential toward EK. If the cell were at around -70 mV, -60 mV, or -50 mV, that would imply a less negative interior and closer to threshold, which isn’t characteristic of resting cardiac tissue. Hence the resting potential is approximately -90 mV.

The resting membrane potential in cardiac myocytes is set mainly by potassium conductance, so the membrane sits close to the potassium equilibrium potential, which is about -90 mV. The Na+/K+ pump maintains the ion gradients that make this possible, but at rest the membrane is most permeable to K+, driving the potential toward EK. If the cell were at around -70 mV, -60 mV, or -50 mV, that would imply a less negative interior and closer to threshold, which isn’t characteristic of resting cardiac tissue. Hence the resting potential is approximately -90 mV.