MUSCLE PHYSIOLOGY

Detailed explanation-1: -Troponin, which regulates the tropomyosin, is activated by calcium, which is kept at extremely low concentrations in the sarcoplasm. 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.

Detailed explanation-2: -Troponin binds to tropomyosin and helps to position it on the actin molecule; it also binds calcium ions. To enable a muscle contraction, tropomyosin must change conformation, uncovering the myosin-binding site on an actin molecule and allowing cross-bridge formation.

Detailed explanation-3: -Bottom panel: Calcium (Ca2+) binds to troponin C, leading to a conformational change which moves the tropomyosin molecule and makes the myosin binding site accessible to the myosin head. The other troponins also contribute to this process.

Detailed explanation-4: -Troponin T (TnT) binds to tropomyosin (Tm) to anchor the troponin complex in the thin filament, and it thus serves as a vital link in the Ca2+ regulation of striated muscle contraction.