1. Nerve impulse triggers release of Acetyl Choline [neurotransmitter] from the synaptic knob into the synaptic cleft
2. ACh binds to ACh receptors in the motor end plate of the neuromuscular junction, initiating a muscle impulse in the sarcolemma of the muscle fiber
3. As the muscle impulse spreads quickly from the sarcolemma along T tubules, calcium ions are released from terminal cisternae into the sarcoplasm
4. Calcium ions bind to troponin
5. Troponin changes shape, moving tropomyosin on the actin to expose active sites on actin molecules of thin filaments
6. Myosin heads of thick filaments attach to exposed active sites to form crossbridges
7. Myosin heads pivot, moving thin filaments toward the sarcomere center. ATP binds myosin heads and is broken down into ADP and P
8. Myosin heads detach from thin filaments and return to their prepivot position
9. The sarcomere shortens and the muscle contracts
10. When the impulse stops, calcium ions are actively transported into the sarcoplasmic reticulum
11. Tropomyosin re-covers active sites, and filaments passively slide back to their relaxed state