Chap08 - Outline Structure of Skeletal Muscle Neuromuscular...

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Outline Structure of Skeletal Muscle Neuromuscular Junction Muscular Contraction Sliding Filament Model Energy for Contraction Regulation of Excitation-Contraction Coupling Fiber Types Skeletal Muscle 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 Muscle actions Flexors Decrease joint angle Extensors Increase joint angles Connective Tissue Covering Skeletal Muscle Epimysium Surrounds entire muscle Perimysium Surrounds bundles of muscle fibers Fascicles Endomysium Surrounds individual muscle fibers External lamina Just below endomysium Sarcolemma Muscle cell membrane Connective Tissue Surrounding Skeletal Muscle
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Satellite Cells Play role in muscle growth and repair Increase number of nuclei Myonuclear domain Cytoplasm surrounding each nucleus Each nucleus can support a limited myonuclear domain More nuclei allow for greater protein synthesis Important for adaptations to strength training Microstructure of Skeletal Muscle Microstructure of Muscle Fibers Myofibrils Contain contractile proteins Actin (thin filament) Myosin (thick filament) Sarcomere Includes Z line, M line, H zone, A band, I band Sarcoplasmic reticulum Storage sites for calcium Terminal cisternae Transverse tubules Extend from sarcolemma to sarcoplasmic reticulum
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The Sarcoplasmic Reticulum and Transverse Tublules Neuromuscular Junction Junction between motor neuron and muscle fiber Motor unit Motor neuron and all fibers it innervates Motor end plate Pocket formed around motor neuron by sarcolemma Neuromuscular cleft Short gap between neuron and muscle fiber Acetylcholine is released from the motor neuron Causes an end-plate potential Depolarization of muscle fiber The Neuromuscular Junction
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The Sliding Filament Theory Muscle shortening occurs due to the movement of the actin filament over the myosin Filament. Formation of cross-bridges between actin and myosin filaments Power stroke Reduction in the distance between Z lines of the sarcomere The Sliding Filament Theory of Contraction Energy for Muscle Contraction ATP is required for muscle contraction Myosin ATPase breaks down ATP as fiber contracts ATP ADP + P i Sources of ATP Phosphocreatine (PC) Glycolysis Oxidative phosphorylation
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Chap08 - Outline Structure of Skeletal Muscle Neuromuscular...

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