muscle+contraction+9

The functional unit of a muscle fiber is the sarcomere, this is where the muscle contraction occurs.

The brain sends out a motor nerve which stimulates a muscle contraction. During the muscle contraction the thin filaments are pulled twoard one another. This leads to the shortening of the sarcomere. The myosin heads of the thick filament connect to the myosin binding site on the actin of the thin filament. The myosin heads pivot which slides the thin and thick myofilaments passed each other. As a result, the z-discs of the sarcomere are drawn closer together. For this mechanism to happen there needs to be calcium and energy.