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Skeletal Muscles- Contraction

Skeletal Muscles- Contraction. Prof. K. Sivapalan. Myosin Filament. Myosin has a head and a tail Each filament may have 200 or more myosin molicules The tails are bundled as the body while the heads hang outwards on a small arm – cross bridge The head has ATPase activity

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Skeletal Muscles- Contraction

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  1. Skeletal Muscles- Contraction Prof. K. Sivapalan

  2. Myosin Filament • Myosin has a head and a tail • Each filament may have 200 or more myosin molicules • The tails are bundled as the body while the heads hang outwards on a small arm – cross bridge • The head has ATPase activity • The cross bridge is flexible at hinges Skeletal Muscle Contraction

  3. Contraction Skeletal Muscle Contraction

  4. Sliding of Actin on Myosin • At rest ATP binds to the head of the myosin, converted to ADP, the energy stored in the head. • At this state, the head is perpendicular to the filament. • When binding site of the actin is exposed, actin – myosin binding occurs. • This binding changes the conformation of the cross bridge and causes ‘power stroke’ with energy stored as a ‘cocked spring’ • the stroke results in detachment of the cross bridge, release of ADP and attachment of another ATP Skeletal Muscle Contraction

  5. Muscle Twitch- Experimental Design Skeletal Muscle Contraction

  6. Muscle Twitch • When one single stimulus is given, the muscle contracts and relaxes after a latency • The latency is the time taken for excitation- contraction coupling Skeletal Muscle Contraction

  7. Staircase Phenomenon Skeletal Muscle Contraction

  8. Summation Skeletal Muscle Contraction

  9. Tetanization Skeletal Muscle Contraction

  10. Length – Strength • The force developed by the muscle depends on the length of the muscle. • It increases to maximum and then decreases. Skeletal Muscle Contraction

  11. Actin-Myosin Overlap and Tension Developed • When muscle shortened, action myosin linkages are less. • When the length increases, more and more linkages become possible • When over stretched, again linkages are less Skeletal Muscle Contraction

  12. Motor Units and Strength • Muscle fibers innervated by one axon constitute one motor unit. • The size of the motor unit is the number of muscle fibers in it. • The tension developed will depend on the number of myofibriles in each fiber and the size of the motor unit. Skeletal Muscle Contraction

  13. Electromyography- EMG Skeletal Muscle Contraction

  14. Skeletal Muscle Contraction

  15. Effects of Denervation • Atrophy – less myofibrils • Fibrillations- receptor hypersensitivity • Fasciculation – motor unit function Skeletal Muscle Contraction

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