briefly describe sliding filament theory

  1. Impulse arrives at neuromuscular junction, and releases acetylcholine. This causes depolarisation and release of Calcium ions from the sarcoplasmic reticulum.
  2. Calcium ions bind to troponin bringing a change in its shape so that tropomyosin moves from the active site of actin.
  3. Myosin filaments bind to actin forming cross-bridges.
  4. The muscle filament shortens in size because ATP releases energy which is used by the myosin to pull the actin filaments. 
  5. An ATP molecule binds to the myosin head which detaches the myosin from actin.
  6. Muscular contraction continues till there is enough ATP and Calcium ions. Once the impulse stops, actin returns to its resting position and all Calcium ions are pumped back to the sarcoplasmic reticulum. 

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