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APK3110_Chapter8_Spring12+partA_without+movies

APK3110_Chapter8_Spring12+partA_without+movies - SKELETAL...

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SKELETAL MUSCLE: STRUCTURE AND FUNCTION Chapter 8 Part A
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Objectives 1. Draw and label the microstructure of skeletal muscle. 2. Define satellite cells. How do these cells differ from the nuclei located within skeletal muscle fibers? 3. List the chain of events that occur during muscular contraction. 4. Define both dynamic and static exercise . What types of muscle action occur during each form of exercise? 5. What three factors determine the amount of force produced during muscular contraction? 6. List the three human skeletal muscle fiber types. Compare and contrast the major biochemical and mechanical properties of each. 7. How does skeletal muscle fiber type influence athletic performance? 8. Graph and describe the relationship between movement velocity and the amount of force exerted during muscular contraction.
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Muscles Human body contains over 400 skeletal muscles 40-50% of total body weight Functions of skeletal muscle Force production for locomotion and breathing Force production for postural support Heat production during cold stress
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Origin : End of muscle that is attached to a bone that does not move Insertion : End of muscle that is attached to a bone that is moved during muscular contraction
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Muscle actions
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Muscle cells (fibers) Nerve tissue Blood vessels Connective tissue Tissues in skeletal muscle
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Connective tissue surrounding skeletal muscle Figure 8.1 1. Fascia a. Separates individual muscles and holds them in position 2. Epimysium a. Surrounds entire muscle 3. Perimysium a. Surrounds bundles of muscle fibers b. Fascicles 4. Endomysium a. Surrounds individual muscle fibers 5. External lamina (basement membrane) a. Just below endomysium 6. Sarcolemma a. Muscle cell membrane 1 2 3 4 6 3b
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Muscle cells (fibers) Unique shape Contain same organelles with other cells mitochondria, lysosomes etc But they are multinucleated (have many nuclei) Striated appearance Stripes produced by alternating dark and light bands Each muscle fiber extends the entire length of the muscle Cell membrane is called the sarcolemma Above the sarcolemma and below the external lamina are a group of muscle precursor cells called satellite cells
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Satellite cells Undifferentiated cells involved in muscle growth and repair If muscle cells are destroyed due to injury or disease they cannot be replaced by cell division Satellite cells can be activated to increase number of nuclei Increasing the number of nuclei allows for greater protein synthesis Important for adaptations to strength training
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During growth, to maintain a constant ratio of cell volume per nucleus, nuclei from satellite cells are incorporated. hypertrophy - increased number of nuclei by activating satellite cells atrophy - decreased number of nuclei Myonuclear domain is the volume of cytoplasm (sarcoplasm) surrounding each nucleus Each nucleus can support the gene expression (protein synthesis) of a limited myonuclear domain
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Microstructure of muscle fibers Myofibrils Threadlike structures contain contractile proteins Figure 8.2 2 major filaments:
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