C -89 Dr. Kennon M. GarrettMUSCLE CONTRACTION Reading: Widmaier et al., Vander’s Human Physiology, 12th ed., pp. 251-259. Behavioral Objectives 1. Describe the microanatomy of skeletal muscle fibers. 2. List the steps of the cross bridge cycle. 3. Describe the functions of actin, troponin and tropomyosin. 4. List the steps of excitation-contraction coupling. 5. Describe how intracellular Ca++levels increase and are regulated. 6. List the steps involved in producing a muscle contraction beginning with the excitation of a neuron in the cerebral cortex through sequestration of Ca++and relaxation of the muscle. I. Organization of muscleA. Types of muscle Figure 9-1
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C -90 1. Striated – banding pattern in muscle seen under polarized light. Banding is due to organization of myofilaments within the muscle cell. a. Skeletal muscle – connected to bone & responsible for movement of skeleton, under voluntary control b. Cardiac muscle - heart muscle, spontaneous contractions regulated by the autonomic nervous system. 2. Smooth – bundles of muscle fibers surrounding hollow organs or tubes, regulated by the autonomic nervous system and local chemical signals. B. Skeletal muscle structure The whole skeletal muscle is made up of bundles of muscle cells. The bundles are called fascicles, and are surrounded by connective tissue Muscle fibers–Muscle cells are called muscle fibers. Skeletal muscle fibers are oriented along the longitudinal axis of the muscle. Muscle fiber cell division stops at birth, however, fibers can increase in size.If muscle cells are injured,satellite cells can differentiate into muscle cells after birth.