4, 1, 3, 6, 2, 5
4. The impulse arrives at the synapse and travels through the transverse tubules.
1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released.
3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites.
6. Tropomyosin molecules bind to exposed active sites, linking actin and myosin
2. Thin filaments are pulled over the thick filaments.
5. The muscle fiber shortens and contracts.