MUSCLE PHYSIOLOGY

Detailed explanation-1: -If present, calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin. Once the tropomyosin is removed, a cross-bridge can form between actin and myosin, triggering contraction.

Detailed explanation-2: -It binds with Troponin C and thus helps the myosin head to tighten onto the actin filament and to begin contraction of the muscles. Thus, the correct answer is option B. i.e., To bind with troponin, changing its shape so that the actin filament is exposed.

Detailed explanation-3: -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-4: -Calcium triggers contraction by reaction with regulatory proteins that in the absence of calcium prevent interaction of actin and myosin. Two different regulatory systems are found in different muscles.