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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
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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) • AChbinds 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 cross-bridges • The muscle fiber shortens as a contraction occurs