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Myology, the study of muscles

Myology, the study of muscles. Three different types of muscle. Skeletal Move skeleton Striated Voluntary Cardiac Striated Involuntary Autorhythmicity Smooth Not striated Usually involuntary Some autorhythmicity. Major functions of muscle. Regulating movement

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Myology, the study of muscles

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  1. Myology, the study of muscles

  2. Three different types of muscle • Skeletal • Move skeleton • Striated • Voluntary • Cardiac • Striated • Involuntary • Autorhythmicity • Smooth • Not striated • Usually involuntary • Some autorhythmicity

  3. Major functions of muscle • Regulating movement • Stabilizing body positions • Movement of materials around body • Regulating body temperature • Properties: • Excitability • Contractility • Extensibility • Elasticity

  4. Organization of skeletal muscle • Superficial fascia separate muscle from skin • Deep fascia separate groups of muscles from each other • Epimysium-entire muscle • Perimysium-fascicle • Endomysium- individual muscle fibers

  5. Organization of a muscle fiber

  6. “Sarco” refers to muscle • Sarcolemma-excitable membrane (T tubules) • Sarcoplasm- glycogen, myoglobin, myofibrils • Sarcoplasmic reticulum • Stores calcium • Triad- regulates calcium movement

  7. Organization of the sarcomere

  8. Muscle proteins • Contractile proteins • Actin, myosin • Regulatory proteins • Tropomyosin, troponin • Structural proteins • Titin, myomesin, dystrophin

  9. Sliding filament model

  10. The sliding filament mechanism

  11. Roles of actin and myosin

  12. The neuromuscular junction

  13. Many drugs affect muscle function through effects on NMJ • Botulism toxin • Prevents release of acetylcholine • Curare • Blocks ACh receptors • Tetanus toxin • Blocks inhibitory neurons

  14. Importance of Ach function Botox treatment Myasthenia gravis

  15. Muscle tone • Subset of muscle fibers produces continuous contraction • Stabilizes but does not contribute to movement in skeletal muscles • Too much: rigidity, too little- spasticity • Electrolyte imbalance • Important in smooth muscle function

  16. Types of muscle fibers • Red and white • Slow oxidative fibers • Lots of mitochondria, myoglobin • Good blood supply (oxygen) • Postural muscles • Endurance

  17. More muscle fibers (p. 277) • Fast glycolytic fibers • Largest; most powerful contractions • Poor blood supply (“white” fibers”) • Lots in arm muscles • Fatigue easily • Fast oxidative-glycolytic fibers • Intermediate • Use ATP faster than slow fibers • Lots in leg muscles

  18. Cardiac muscle is specialized in the heart

  19. Smooth muscle • Single-unit • Most common • Autorhythmic • Stimulation of one fiber spreads to another • Multiple-unit • Larger arteries, lungs, etc. • Only stimulated fiber is affected

  20. Unique features of smooth musclecompared to skeletal muscle: • Smooth muscle has longer, slower contraction • Calcium regulation method is different • Can stretch and still be able to contract • Best at regeneration • See p. 281

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