Do non-pacemaker cells have a resting potential?

Do non-pacemaker cells have a resting potential?

• A. Yes; true resting potential
• B. No resting potential
• C. Resting potential varies
• D. No resting potential but diastolic baseline

Answer: (A)

Non-pacemaker cardiac cells have a stable resting membrane potential. In atrial and ventricular myocytes, this resting potential sits around −85 to −95 mV and is kept negative mainly by inward-rectifier potassium currents that clamp the cell near the K+ equilibrium potential. This stable base is essential because it sets the stage for a rapid, all-or-none depolarization when voltage-gated Na+ channels open, followed by the plateau phase. Pacemaker cells, by contrast, do not sit at a fixed resting potential; they undergo diastolic depolarization due to If and other currents, so their membrane potential drifts upward toward threshold. That’s why non-pacemaker cells are described as having a true resting potential, whereas pacemaker cells exhibit automaticity.

Non-pacemaker cardiac cells have a stable resting membrane potential. In atrial and ventricular myocytes, this resting potential sits around −85 to −95 mV and is kept negative mainly by inward-rectifier potassium currents that clamp the cell near the K+ equilibrium potential. This stable base is essential because it sets the stage for a rapid, all-or-none depolarization when voltage-gated Na+ channels open, followed by the plateau phase.

Pacemaker cells, by contrast, do not sit at a fixed resting potential; they undergo diastolic depolarization due to If and other currents, so their membrane potential drifts upward toward threshold. That’s why non-pacemaker cells are described as having a true resting potential, whereas pacemaker cells exhibit automaticity.