MEDICAL PHYSIOLOGY

Detailed explanation-1: -A thin filament of myofibril contains 2 ‘F’ actins and two other proteins, namely troponin and tropomyosin. Tropomyosin and troponin regulate muscle contraction. Troponin binds to the calcium ions and removes the tropomyosin from the actin myosin binding site which allows the muscle contraction.

Detailed explanation-2: -Thin filaments are composed primarily of the contractile protein actin. As illustrated in Figures 2-8, A and B, actin is composed of small globular subunits (G actin) that form long strands called fibrous actin (F actin).

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