Place the five phases of a myocardial action potential in correct order.
1)Fast sodium channels are inactivated
2)Cell returns to its "resting" state
3)"Plateau" phase
4)Initial rapid depolarization of myocardial tissues
5)Calcium channels close

Question

Quizplus · Accepted Answer

Phase 0: Initial rapid depolarization of myocardial tissues caused by an abrupt transmembrane influx of sodium through "fast" sodium channels. Phase 1: Fast sodium channels are inactivated;this,coupled with the movement of K⁺ and Cl^- ions,leads to a transient net outward current and the beginning of repolarization. Phase 2: "Plateau" phase,maintained by a balance between calcium influx and potassium efflux. Phase 3: Calcium channels close,but membrane remains permeable to potassium,resulting in cellular repolarization. Phase 4: Cell returns to its "resting" state;resting membrane potential is reached through gradual depolarization related to a constant sodium influx balanced by a decreasing efflux of potassium.

Place the Five Phases of a Myocardial Action Potential in Correct