How does the muscle contract?
When the sarcoplasmic reticulum is depolarized, calcium ions enter the cell and bind to troponin.
This causes a conformational change that allows exposure of the actin-binding site to myosin.
The myosin attaches to the actin-binding site and flexes, causing the actin filament to slide by the myosin filament.
Adenosine triphosphate is required to allow the myosin-actin crossbridge to release and the muscle to relax.
