What is the first event in muscle fiber contraction?
A. Acetylcholine is released from the end of the motor neuron.
B. Acetylcholine diffuses across a gap at a neuromuscular junction.
C. Calcium ions diffuse from sarcoplasmic reticulum into the sarcoplasm and bind to troponin molecules.
D. The muscle fiber membrane is stimulated and a muscle impulse travels deep into the fiber through transverse tubules.
Answer: A
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