MUSCLE PHYSIOLOGY

Detailed explanation-1: -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-2: -Individual actin filaments are assembled into two general types of structures, called actin bundles and actin networks, which play different roles in the cell (Figure 11.6). In bundles, the actin filaments are crosslinked into closely packed parallel arrays.

Detailed explanation-3: -There are about 300-400 globular actin molecules attached from end to end to form the helical strands of the thin filament, now called F actin (being fibrous). Each actin molecule has a binding site for a myosin cross bridge or head during the process of contraction. Another protein in the thin filament is troponin.