Question

Identify the true statement regarding the point marked(Red) on the myocardial action potential curve?

• A. Due to the opening of Na+ and closure of fast K+ channels
• B. Due to the slow but prolonged opening of Ca2+ channels
• C. Due to the closure of Na+ and opening of the slow K+ channel
• D. Due to Na+/K+ ATPase

Answer 1

The Correct Option is B

The myocardial action potential curve is characterized by distinct phases: Phase 0 (rapid depolarization), Phase 1 (initial repolarization), Phase 2 (plateau), Phase 3 (final repolarization), and Phase 4 (resting potential). The point marked in red is typically associated with Phase 2, known as the plateau phase. During this phase, the cell membrane potential remains relatively stable.

In this phase, the key ionic movement is the slow influx of Ca²⁺ ions through L-type calcium channels, counterbalanced by the efflux of K⁺ ions. As the Ca²⁺ channels open slowly but remain active for a prolonged period, they counteract repolarization, resulting in a plateau in the action potential.

Thus, the true statement regarding the point marked on the myocardial action potential curve is:

Due to the slow but prolonged opening of Ca²⁺ channels.