MUSCLE PHYSIOLOGY

Detailed explanation-1: -The myofilament contractile proteins consist of thick filament myosin and thin filament actin proteins. Bound to actin are a complex of regulatory proteins, which include tropomyosin and troponin-T, C, and I.

Detailed explanation-2: -Thick filaments occur only in the A band of a myofibril. Thin filaments attach to a protein in the Z disc called alpha-actinin and occur across the entire length of the I band and partway into the A band.

Detailed explanation-3: -Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the contractile proteins and titin is an elastic protein.

Detailed explanation-4: -Myosin, the back-bone of the thick filament, slides past actin thin filaments by hydrolyzing adenosine triphosphate (ATP) to mediate muscle contraction (255, 256).

Detailed explanation-5: -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).