MEDICAL PHYSIOLOGY

Detailed explanation-1: -Tropomyosin winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin. The troponin-tropomyosin complex uses calcium ion binding to TnC to regulate when the myosin heads form cross-bridges to the actin filaments.

Detailed explanation-2: -Tropomyosin covers the actin binding sites, preventing myosin from forming cross-bridges while in a resting state.

Detailed explanation-3: -Tropomyosin blocks myosin binding sites on actin molecules, preventing cross-bridge formation and preventing contraction in a muscle without nervous input.

Detailed explanation-4: -This is because myosin binding sites on the actin filaments are all covered by a rod-shaped protein called tropomyosin.

Detailed explanation-5: -Tropomyosin serves to block the active site on actin, thereby inhibiting actin and myosin from binding under resting conditions. Troponin is a small, globular protein complex composed of three subunits that control the position of the tropomyosin (Figure 2-9).