1. Neuromuscular Junction and Major Events of Muscle Contraction Quiz Review

2. Major Events of Muscle Contraction A nerve impulse travels down a motor neuron axon The motor neuron terminal releases the neurotransmitter acetylcholine ( ACh) ACh binds to ACh receptors The sarcolemma is stimulated, and a muscle impulse travels over the surface of the muscle fiber and deep into the fiber through the transverse tubules

3. The muscle impulse reaches the sarcoplasmic reticulum and calcium channels open Calcium ions diffuse from the sarcoplasmic reticulum into the sarcoplasm and bind to troponin molecules Tropomyosin molecules move and expose specific sites on actin

4. Actin and myosin form linkages Thin (actin) filaments are pulled toward the center of the sarcomere by myosin cross- bridges The muscle fiber shortens as a contraction occurs