During which phase of the action potential does muscle contraction occur?

Muscle contraction occurs during Phase 2 of the action potential, often referred to as the plateau phase. During this phase, there is a prolonged depolarization of the cell membrane due to the influx of calcium ions through L-type calcium channels. This sustained depolarization is crucial as it allows for a significant amount of calcium to enter the cardiac myocytes, which triggers the contractile machinery of the muscle fibers.

The presence of calcium ions binds to troponin, leading to a conformational change that allows the actin and myosin filaments to interact, resulting in muscle contraction. This mechanism is critical for the effective pumping action of the heart, ensuring coordinated contraction during the cardiac cycle. The characteristics of Phase 2 are essential not only for contraction but also for preventing tetanus in cardiac tissue, allowing for proper rhythmic heartbeats.