Steps of the Sliding Filament Theory

1. An action potential crosses the neuromuscular junction. This causes the muscle cell to depolarise. After that occurs, it spreads down the transverse tubules to the sarcoplasmic reticulum.
2. Then, the calcium channels open. This is due to stimulation of the sarcoplasmic reticulum. This releases the stored calcium ions into the sarcoplasm when there is a nerve signal.
3. Actin-Myosin binding sites are exposed. After that, the calcium ions bind to the protein on tropomyosin. This changes the shape of the protein. This moves the tropomyosin and exposes the binding sites.
4. THe Myosin head binds with the actin-myosin binding sites. This shortens the sacromere. These myosin heads create bonds with the actin filament. This is called actin-myosin cross-bridges.
5. ATP binds to the myosin head and causes it to detach from the actin filament. 
6. The ATP is hydrolyzed to ADP and phosphate. This pushes the myosin head into its high energy position and gets ready to form a new crossbridge. 
7. This cycle leads to sustained muscle contraction,