Figure 3: Structure of myosin and actin filaments and their arrangement within a sarcomere. (A) Diagram of a myosin molecule. (B) Arrangement of myosin molecules to form a myosin filament. Note that the myosin filament is symmetrical with respect to central bare zone (or bare region), and that myosinheads (S1) extends from the filament except for bare zone. (C) arrangement of actin monomers (G-actin) in an actin filament. Note that the actin filament contains tropomyosin and troponin. (D) Arrangement of actin and myosin filaments within a sarcomere. Note that the half sarcomeres at both sides of the bare zone are structural and functional units of striated muscle [10].