What are the major events of muscle contraction and relaxation?

Muscle contraction and relaxation occurs over a series of synchronized steps. The major events of muscle contraction and relaxation are:

• A nerve impulse from the brain or spinal cord arrives at the neuromuscular junction and causes the release of Acetycholine, which binds to receptors on the muscle fiber membrane, initiating the start of muscle contraction. 
• Calcium ions are released from the sarcoplasmic reticulum.
• Calcium ions bind to troponin, exposing active sites on actin filaments, enabling myosin heads to bind to the actin filament. 
• ATP binds to the myosin head and is hydrolyzed to ADP and potassium. This releases energy, which is used to power the power stroke of the myosin head. The power stroke is the movement of the myosin head towards the M-line, which pulls the actin filament along with it.
• The repeated power strokes of the myosin heads cause the actin filaments to slide past the myosin filaments, shortening the muscle fiber and causing a contraction.
• The myosin head detaches from the actin filament and breaks the cross-bridge formation, allowing the muscle to relax. 
• The freed myosin head attaches to another ATP molecule, repeating the process.