Neuromuscular Junction and Major
Events of Muscle Contraction
Quiz Review
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
• 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
• Actin and myosin form linkages
• Thin (actin) filaments are pulled toward the
center of the sarcomere by myosin crossbridges
• The muscle fiber shortens as a contraction
occurs