Crossbridge Theory
In order for contraction to occur, the "energized" MYOSIN crossbridge must first attach to ACTIN. The Sites Where Myosin Attach On The Actin Filament Are Covered With Tropomyosin
- Basically, the sites are unavailable for crossbridging.
Troponin Is Bound To The Tropomyosin Molecule.
When Ca++ presents itself inside the sarcomere, it binds with troponin to pull the tropomyosin molecule away from the active sites on the ACTIN filament.