What is the sliding filament mechanism?
The sliding filament mechanism is a model used to show the way in which muscles contract. It involved 3 components - Myosin, Actin and Tropomyosin. Myosin has a head like projection to which an ADP molecule is attaced. Actin is a seperate filament which has a binding site covered by the tropomyosin. When a nerve impulse reaches the neuro-muscular junction, Ca2+ ions are released by the sarcoplasmic reticulum, causing tropomyosin to move, exposing the actin binding site. The myosin head binds to this site - releasing its ADP in the process. The myosin head changes angle, moving the actin along, called the power stroke. An ATP molecule binds to the myosin head causing it to be released (as a result of hydrolysis, reforming the mysoin-ADP). This process repeats and causes the actin filaments to 'slide' along the myosin filaments. A good analogy of this would be rowers in a boat gliding across the water, with their ores acting as myosin heads.
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