Mark Paternostro • West Virginia University Lauralee Sherwood Chapter 8 Muscle Physiology
Fig. 7-‐5a, p. 250
Muscle pp. 258-270 • Comprises largest group of tissues in body • 3 types of muscle – Skeletal muscle • Make up muscular system – Cardiac muscle • Found only in the heart – Smooth muscle • Appears throughout the body systems as components of hollow organs and tubes • Classified in 2 different ways – Striated or unstriated – Voluntary or involuntary
Fig. 8-1, p. 259
Fig. 8-2a, p. 260 (a) Relationship of a whole muscle and a muscle fiber Connective tissue Muscle fiber (a single muscle cell) Tendon Muscle
Fig. 8-2, p. 260 10-100 microns in diameter 750,000 microns (2.5 ft) in length Formed by fusion of myoblasts, therefore multiple nuclei in muscle cell
Structure of Skeletal Muscle • Myofibrils – Contractile elements of muscle fiber – Regular arrangement of thick and thin filaments • Thick filaments – myosin (protein) • Thin filaments – actin (protein) – Viewed microscopically myofibril displays alternating dark (the A bands ) and light bands (the I bands ) giving appearance of striations 12-18 nm diameter; 1.6 microns long 5-8 nm diameter 1 micron long NOTE: actin & myosin are often called “ contractile proteins ” ; however, neither contracts!!!!!!!!!!!!!!!!!
Fig. 8-3a, p. 261 M line Sarcomere Z line Z line I band A band H zone (a) Electron micrograph of a myofibril
Structure of Skeletal Muscle • Sarcomere – Functional unit of skeletal muscle – Found between 2 Z lines (connects thin filaments of two adjoining sarcomeres) – Regions of sarcomere • A band – Made up of thick filaments along with portions of thin filaments
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- Fall '08