BISC 104Lxg Lecture 7: BISC 104 Notes - Muscular System
11 Feb 2017
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Contraction = formation of cross bridges between thin and thick filaments. Actin and myosin are microscopic proteins that interact and cause the entire muscle tissue to shorten, and thus, move the skeletal tissue. According to sliding filament model, a muscle contracts when actin filaments slide past myosin filaments, shortening the sarcomere. Myosin molecules are shaped like two-headed golf clubs. The club-shaped myosin heads are key to moving actin filaments. The myosin head, also known as a cross-bridge, attaches to a nearby actin filament. Head bends and swivels, pulling the actin filament toward the midline of the sarcomere. The myosin head disengages from the actin filament. Muscle contraction will occur as long as atp is present. Within three to four hours after death, the muscles become stiff = rigor mortis. Actin and myosin gradually break down and muscles relax again after two to three days. Skeletal muscle fiber contracts only when stimulated by a motor neuron.
