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Muscle Tissue

Muscle Tissue. Muscle tissue functions Movement Maintain Posture Joint stabilization Heat generation. (11.5a). Muscle tissue properties. Contractility Excitability Extensibility Elasticity. (11.5a). Muscle tissue types. Skeletal Striated, voluntary Cardiac

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Muscle Tissue

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  1. Muscle Tissue Muscle tissue functions Movement Maintain Posture Joint stabilization Heat generation (11.5a)

  2. Muscle tissue properties • Contractility • Excitability • Extensibility • Elasticity (11.5a)

  3. Muscle tissue types • Skeletal • Striated, voluntary • Cardiac • Heart, striated, involuntary • Smooth • Nonstriated, involuntary Table 10.2

  4. Muscle tissue terminology • Myofiber – A skeletal, cardiac or smooth muscle cell • Myofilaments Protein “threads” within a myofiber1.Actin – thin filaments 2. Myosin – thick filaments • Sarcolemma – plasma membrane • Sarcoplasm – cytoplasm

  5. Skeletal Muscle C.T. • Epimysium – surrounds entire muscle/organ • Perimysium – surrounds muscle fascicle • Endomysium – surrounds individual muscle fiber (10.1a)

  6. THE CONNECTIVE TISSUE WRAPPINGS – A VIEW

  7. Skeletal Myofiber (muscle fiber) • Cylindrical • 10-100 m diameter • Varied length – up to entire muscle • Formed by cell fusion • Multinucleated • Peripheral nucleus • Striated • LM Demonstration Table 10.2

  8. Sliding filament theory • Muscle contracts by actin and myosin sliding past each other • Myosin forms cross-bridges that attach to actin • Cross bridges all swing in same direction and pull actin along • Increased overlap of filaments results in contraction of muscle (10.6)

  9. Sliding filament theory • Actin and myosin do not shorten • A band does not change • I band shortens • Sarcomere shortens (10.7)

  10. The Neuromuscular junction • Neuromuscular Junction • Axon terminal • Mitochondria • Synaptic vesicles – ACh • Synaptic cleft • Motor end plate • AChR • AP to muscle fiber (14.5ab)

  11. Sarcoplasmic reticulum • SR surrounds each myofibril • Stores Ca++ • Release Ca++ for contraction • Ca++ uptake for relaxation (10.8)

  12. Muscle contraction • Signal to axon terminal • ACh released • AChR activated • Muscle excited • Excitation travels down t-tubule • SR releases Ca++ • Ca++ activates sliding filament process • Muscle contracts http://www.blackwellpublishing.com/matthews/myosin.html (14.5b)

  13. VIEW OF MYOFILAMENT STRUCTURES

  14. Motor Unit • Definition: a motor neuron and all the muscle fibers it innervates. • When a motor neuron fires, all muscle fibers in the motor unit contract. • All or none principle • A motor unit may contain hundreds to four muscle fibers (average ~ 150) • Each muscle fibers receives one NMJ (14.6)

  15. Summary: skeletal muscle fibers muscle myofibril fascicle Table 10.1 fiber Myofilaments :actin & myosin

  16. Cardiac muscle • Only in heart • Sliding filament theory • Striated • No NMJ 18.4

  17. Cardiac muscle cells • 15 m wide X 100 m long • Branched • Intercalated discs • Desmosomes • adhesion • Gap junctions • transmit electrical impulses • Forms two networks – atrial and ventricular (10.10a)

  18. Cardiac muscle cells (10.10cd) • Central 1-2 nuclei • Mitochondria – numerous • Less SR • Fewer T tubules • Myofibrils • Sarcomeres • A band • I band • Z disc • H zone • Striated

  19. Smooth muscle • Six major locations • Blood vessels • Respiratory system • Digestive system • Urinary system • Reproductive system • Eye (lens and iris) • Siding filament theory applies • Actin & myosin • No myofibrils – no striations

  20. Smooth muscle fibers • Spindle shaped • 2-10 m diameter • 20-200 m long • Nonstriated • Central nucleus • Arranged in sheets • Usually in layers around a tube • Peristalsis - waves of contraction to propel contents along tube (10.12b)

  21. Smooth muscle properties • Slower to contract vs. skeletal muscle • Slower to relax vs. skeletal muscle • Can maintain contraction longer • Resistant to fatigue • Unconscious control • ANS – autonomic nervous system • Stretch • Hormones

  22. Smooth muscle organization • Single unit innervation • Smooth muscle fibers connected by gap junctions • Network receives single innervation • Coordinated contraction • Multiunit innervation • Each fiber innervated • Locations • Iris of eye • Arrector pili muscle of skin

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