What mechanism allows smooth muscle to resist fatigue during prolonged contraction?

The latch-bridge mechanism is a crucial feature of smooth muscle physiology that allows it to maintain prolonged contractions without significant fatigue. This mechanism involves the prolonged attachment of myosin heads to actin filaments, which allows smooth muscle to sustain a contraction with relatively low energy consumption.

In this latch state, the myosin heads remain bound to actin for extended periods, which generates tension without the need for continuous ATP hydrolysis. This is particularly important for functions such as maintaining vascular tone or regulating gut motility, where long-lasting contractions are needed without depleting energy reserves rapidly.

Unlike in skeletal muscle, where contraction relies heavily on rapid cycles of cross-bridge formation and detachment that consume large amounts of ATP, smooth muscle's ability to engage in the latch-bridge mechanism facilitates endurance and efficiency. This allows smooth muscle to remain contracted for extended periods with minimal fatigue, making it well-suited for its roles in various involuntary movements in the body.