MUSCLE PHYSIOLOGY

Detailed explanation-1: -Final answer: The thin filament of a myofibril is a complex of three different proteins called actin, tropomyosin, and troponin.

Detailed explanation-2: -Thin filaments are comprised of two actin strands, each harboring equally separated troponin complexes, which bind Ca2+ to move tropomyosin cables away from the myosin binding sites and, thus, activate systolic contraction.

Detailed explanation-3: -The myofibrils are made up of thick and thin myofilaments, which help give the muscle its striped appearance. The thick filaments are composed of myosin, and the thin filaments are predominantly actin, along with two other muscle proteins, tropomyosin and troponin.

Detailed explanation-4: -An individual sarcomere contains many parallel actin (thin) and myosin (thick) filaments. The interaction of myosin and actin proteins is at the core of our current understanding of sarcomere shortening.

Detailed explanation-5: -The thin filaments of differentiated smooth muscle cells are composed of actin and tropomyosin isoforms and numerous ancillary actin-binding proteins that assemble together into distinct thin filament classes.