The sequence of events in muscle contraction (Ch.9)

(1) the sequence of events in muscle contraction

An electrical impulse causes small vesicles at the end of a motor neuron to bind with the cell wall and release the neurotransmitter acetylcholine (ACh).

(2) the sequence of events in muscle contraction

ACh diffuses across the synaptic cleft, where it stimulates receptors in the sarcolemma.

(3) the sequence of events in muscle contraction

An electrical impulse travels over the sarcolemma and inward along the T tubules, causing sacs in the sarcoplasmic reticulum to release calcium.

(4) the sequence of events in muscle contraction

Calcium binds with the troponin on the actin filament, exposing attachment points.

(7) the sequence of events in muscle contraction

Calcium ions are pumped back into the sarcoplasmic reticulum.

(5) the sequence of events in muscle contraction

The myosin heads of the thick filaments grab onto the thin filaments and muscle contraction occurs

(6) the sequence of events in muscle contraction

The release of ACh stops and acetylcholinesterase breaks down any remaining ACh.

(8) the sequence of events in muscle contraction

Troponin and tropomyosin prevent the myosin heads from gasping the thin filament, and the muscle fiber relaxes.