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Muscle Tissue

Muscle Tissue. Functions : movement change size and shape of organs Myofilament : thin filament : actin thick filament : myosin. Classification of Muscle. Striated muscle : skeletal muscle : attached to bone visceral striated muscle restricted to soft tissues cardiac muscle :

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Muscle Tissue

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  1. Muscle Tissue • Functions : • movement • change size and shape of organs • Myofilament : • thin filament : actin • thick filament : myosin

  2. Classification of Muscle • Striated muscle : • skeletal muscle : • attached to bone • visceral striated muscle • restricted to soft tissues • cardiac muscle : • muscle of heart • Smooth muscle : • viscera and vascular system

  3. Skeletal Muscle • Muscle fiber : • fusion of myoblasts • multinucleated cylindrical fiber • sarcolemma : • basal lamina, external lamina, reticular lamina • Connective tissue : • endomysium : reticular fiber surround muscle fiber • perimysium : fascicle • epimysium : dense connective tissue

  4. Skeletal Muscle Types • Red fibers : • slow-twitch motor unit • long, slow contractions, maintain erect posture • White fibers : • fast-twitch motor unit • rapid contractions, fine movements • Intermediate fibers : • Myoglobin : oxygen-binding protein

  5. Myofibrils and Myofilaments • Myofibril : structural and functional subunit • Sarcoplasmic reticulum : sER of muscle • Cross-striations : • A band • H zone • M line • I band • Z line ( Z disc ) • Sarcomere : the basic contractile unit

  6. Myofilaments Arrangement • Thin filaments : • actin : tropomysin, troponin • a-actinin : anchor thin filament at Z disc • nebulin : anchor thin filament at Z disc • Thick filament : • myosin • myomesin : hold myosin filaments • C protein : hold myosin filaments • Titin :elastic protein

  7. Actin Structures • Actin : • F-actin (filamentous actin) • tropomyosin • troponin complex: • torponin-T (TnT) : binds to tropomyosin • torponin-C (TnC) : bind calcium • torponin-I (TnI) : inhibit actinmyosin interaction • G-actin (globular actin)

  8. Myosin Structures • Myosin : • two polypeptide chains double helix • tail to tail • structures • tail • globular head : (cross bridge) • ATP-binding site • ATPase

  9. Regulation of Contraction • Triad : at A band end terminals • Transverse tubular system : • plasma membrane invaginations • membrane depolarization • Terminal cisterna : • sarcoplasmic reticulum • calcium storage and release

  10. Motor Innervation • Motor unit : • Motor neurons • myelin sheath : • Schwann cell (neurilemmal cell), teloglia • motor end plates : • junctional folds • all muscle fiber innervated by single motor nerons • Atrophy :

  11. Sensory Innervation and Repair • Neuromuscular spindle : • modified muscle and capsule • nuclear bag fiber • nuclear chain fiber • primary afferent fibers • g efferent fibers • Tendon organs : • Repair : satellite cells

  12. Cardiac Muscle • Nucleus : • central location • Cross-striation : • like skeletal muscle • Intercalated discs : • fasciae adherentes • maculae adherentes • gap junctions • Branch :

  13. Contraction of Cardiac muscle • Diad : at Z disc • T tubule • terminal cisternae ( sER ) • Spontaneous rhythmic contraction • Cardiac conducting cells (Purkinje cells) • Nervous innervation : modify the rate of contraction • Injury repair by fibrous connective tissue

  14. Smooth Muscle • Fusiform cell • Single center nucleus • Myofilaments : cytoplasmic densities • actin • myosin • dense bodies (similar to Z disc of striated muscle) • No T system

  15. Contraction and Control • Spontaneous contractile activity • Regulatory control : • autonomic nervous system : • sympathetic nerves • parasympathetic nerves • hormones : • oxytocin • no motor end plate formation

  16. Secretion, Repair, and Differentiation • Secretion : • fibers : collagen, reticular, elastin, proteoglycans • hormone : renin • Smooth muscle renew, repair, and differentiation : • undifferentiated mesenchymal cells • pericytes (vessels) • smooth muscle mitosis • myofibroblast • myoepithelial cells (myoid cell)

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