A NERVE IMPULSE arrives at the AXON terminal of the MOTOR NEURON , and releases (ACH), filling SYNAPTIC VESSLES with ACH, which DIFFUSES across SYNAPTIC CLEFT BINDS to its RECEPTORS (MOTOR END PLATE, releasing NA+ which triggers a muscle action potential (MAP).
The MAP travels along T-Tubule OPENING Calcium release CHANNELS in the sarcoplasmic reticulum membrane (SRM), which allows CA-2 IONs to FLOOD into the SARCOPLASM.
Acetylcholinesterase (ACH E) in synaptic cleft DESTROYS EXCESS (ACH), CA-2 BINDS to TROPONIN on ACTIN (thin filaments), EXPOSING the BINDING SITES for MYOSIUM (Calcium levels increase).
Contraction: power strokes use ATP; myosin head binds to actin, thin filaments are pulled toward the center of the sarcomere. (ATTACH, PIVOT, DETACH, RELEASE)
(Calcium active transport pumps)
Calcium RELEASE CHANNELS in SR CLOSE and Calcium active transport pumps use ATP to lower calcium ions levels in sarco-plasm causing the TROPONIN-MYOSIUM COMPLEX to SLIDE BACK into position where it BLOCKS the MYOSIUM ACTIVE SITES ON ACTIN causing muscles to relax