Muscle Cell Contractions

Identify the cause of the muscle cell contraction as the release of calcium ions after a nerve impulse activates the muscle cell membrane

    “Sliding filament theory”

  • Ca2+ ions interact with tropomyosin and troponin, exposing the active sites on the actin filament and allowing the myosin head to bind there.
  • This allows myosin to catalyse the hydrolysis of ATP, resulting in the energy release, which causes the myosin head to move into a higher energy state.
  • The higher energy state permits the head to bind to an active site further along the actin/tropomyosin/troponin strand. This leads to the release of phosphate group and eventually ADP.
  • When the nerve impulse ceases, the myosin head resumes its normal resting position.