MEDICAL 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 and tropomyosin are regulatory proteins that help to regulate the interaction between actin and myosin filaments. The binding of the myosin heads to the muscle actin is a highly regulated process. When a muscle is resting, actin and myosin are separated.

Detailed explanation-3: -Thin-filament regulation of actomyosin interaction is modulated by two actin-binding regulatory proteins: tropomyosin (TM) and caldesmon (CaD).

Detailed explanation-4: -4.1. Visualization of troponin on actin filaments (F-actin). Troponin plays a central role in the calcium-regulation of muscle contraction: Troponin is the sole calcium-binding component of thin filaments (actin-tropomyosin-troponin complex) of striated muscles.

Detailed explanation-5: -Troponin and tropomyosin regulate contraction via calcium binding.