MUSCLE PHYSIOLOGY

Detailed explanation-1: -The given statement is true. Muscle is made up of actin and myosin filament. During muscle contraction, calcium binds with troponin C that moves tropomyosin, and exposes the myosin-binding site on actin.

Detailed explanation-2: -The molecular regulation of striated muscle contraction couples the binding and dissociation of Ca2+ on troponin to the movement of tropomyosin on actin filaments. In turn, this process exposes or blocks myosin binding sites on actin, thereby controlling myosin crossbridge dynamics and consequently muscle contraction.

Detailed explanation-3: -Specifically, troponin (the smaller protein) shifts the position of tropomyosin and moves it away from the myosin-binding sites on actin, effectively unblocking the binding site (Figure 5). Once the myosin-binding sites are exposed, and if sufficient ATP is present, myosin binds to actin to begin cross-bridge cycling.