Physiology 3120 Lecture 6: 6Contraction of Skeletal Muscle

• School: Western University
• Department: Physiology
• Course: Physiology 3120
• Professor: Tom Stavraky

Document Summary

Whole muscle >> fascicle >> muscle cell/muscle fiber >> myofibrils >> myofilaments: myofilaments contain the contractile proteins that cause the muscle to shorten. No. of muscle cells in a whole muscle varies depending on the size of the muscle: larger muscle = more muscle cells. Multinucleated nuclei generally lie under cell membrane. Many mitochondria: atp is essential for muscle contraction and relaxation. Myofibrils are made of thick and thin myofilaments. A globular protein polymerized to form a two-stranded alpha-helical chain. Each globular actin molecule contains a myosin binding site. In the diagram, myosin binding sites are covered by tropomyosin. A rod-shaped protein composed of two alpha-helical protein chains wrapped together in a super coil. Lies in grooves formed by actin molecules covering roughly 6 to 7 actin molecules. In the relaxed muscle, tropomyosin is situated so that it partially covers the myosin binding sites on actin.