Delayed rectifier channels are responsible for which part of cardiac action potential?

Delayed rectifier channels are responsible for which part of cardiac action potential?

• A. Phase 3 repolarization
• B. Phase 0 depolarization
• C. Phase 1 notch
• D. Phase 4 resting potential

Answer: (A)

Delayed rectifier potassium channels are responsible for the outward potassium current that repolarizes the cell during the late phase of the cardiac action potential. After the plateau, these channels (I_Kr and I_Ks) open and drive phase 3 repolarization, bringing the membrane potential back toward the resting level. This contrasts with the rapid depolarization of phase 0 driven by sodium influx, the notch of phase 1 from transient outward potassium current, and the resting potential of phase 4 governed mainly by inward rectifier potassium current.

Delayed rectifier potassium channels are responsible for the outward potassium current that repolarizes the cell during the late phase of the cardiac action potential. After the plateau, these channels (I_Kr and I_Ks) open and drive phase 3 repolarization, bringing the membrane potential back toward the resting level. This contrasts with the rapid depolarization of phase 0 driven by sodium influx, the notch of phase 1 from transient outward potassium current, and the resting potential of phase 4 governed mainly by inward rectifier potassium current.