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Explain sliding filament theory of muscle contraction with neat sketches.

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As per Sliding filament theory, when actin and myosin filaments slide towards each other, muscle contraction takes place.

  • A neural signal reaching to neuromuscular junction releases a neurotransmitter (Acetyl choline) which generates an action potential in the sarcolemma. Once the action potential is generated, calcium channels in the muscle cells open and allow the entry of calcium ions.
  • Increase of Ca ++ levels result in binding of calcium to troponin on the actin filament and bring about conformational changes. This removes the masking of active sites on myosin filaments.
  • Myosin a polymer of meromyosins has a head, arm, and tail as its important parts. The head also called heavy meromyosin (HMM) utilizes the energy from ATP hydrolysis and binds with the active site on actin.
  • This results in formation of a crossbridge between actin and myosin. This pulls the attached actin filaments towards the centre of 'A' band. The Z- line attached to actin are also pulled inwards and contraction of muscle fibre happens.

 

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