Mechanism of Muscular Contraction : Sliding Filament Theory

Mechanism of Muscular Contraction : Sliding Filament Theory

1. Action potential spreads through T tubules. This stimulates release of Ca2+ ions from sarcoplasmis reticulum.
2. Ca2+ ions binds to troponin & rearrange the troponin-tropomyosin complexes. Tropomyosin movesaway to expose binding sites on actin filaments.
3. ATP attaches to myosin head & is hydrolysed into ADP.
4. High energy myosin head binds to exposed binding site on actin filament, forming cross-bridges (actomysosin bridges).
5. Myosin head bends 45 degrees & pull actin filament towards centre of sarcomere. (ADP is released)
6. ATP attaches to myosin head again. Myosin head detaches from binding site, swings back & reattaches again. This is 'ratchet mechanism'. Actin filaments are pulled closer towards centre of sarcomere.
7. Muscle contracts.