Figure 1.

Arrangement of the thick (red, orange) and thin (blue) filaments in the muscle sarcomere. The midpoints of the thick filaments are connected by the M-line (dark red) and the ends of the thin filaments by the Z-line (black), which is considered to define the ends of the sarcomere. The central third of each half thick filament is the myosin binding protein C-containing C zone (orange). Titin (brown) runs from the M-line to the Z-line. The white arrows indicate the forces imposed on the Z and M lines during contraction, and the reversal of filament polarity at those lines. To see this figure in color, go online.