CK12 Life Science

Figure 16.24: The components of muscle contraction. The sacromereis the functional
unit of muscle contraction; it reaches from one Z-line to the next (labeled Z-disk inFigure
16.25). In a relaxed muscle, the actin (thin filament) and myosin (thick filament) overlap.
In a muscle contraction, the filaments slide past each other, shortening the sacromere. This
model of contraction is called the sliding filament model. ( 4 )