A. An electrical impulse travels over the sarcolemma and inward along the T-tubules, causing sacs in the sarcoplasmic reticulum to release calcium. ____ B. The release of ACh stops and acetylcholinesterase breaks down any remaining ACh. _____ C. Troponin and tropomyosin prevent the myosin heads from grasping the thin filament, and the muscle fiber relaxes. _____ D. An electrical impulse causes small vesicles at the end of a motor neuron to release the neurotransmitter acetylcholine (ACh). _____ E. Calcium binds with the troponin on the actin filament, exposing attachment points. _____ F. ACh diffuses across the synaptic cleft, where it stimulates receptors in the sarcolemma. _____ G. Calcium ions are pumped back into the sarcoplasmic reticulum. _____ H. The myosin heads of the thick filaments grab onto the thin filaments and muscle contraction occurs.
Human Anatomy & Physiology I (BIO168)
Sequence of Events for Muscle Contraction
Practice Worksheet
See if you can place the events that occur during muscle contraction and relaxation in their proper order. Insert numbers in the paces provided to order the events in the proper sequence.
_____ A. An electrical impulse travels over the sarcolemma and inward along the T-tubules, causing sacs in the sarcoplasmic reticulum to release calcium.
____ B. The release of ACh stops and acetylcholinesterase breaks down any remaining ACh.
_____ C. Troponin and tropomyosin prevent the myosin heads from grasping the thin filament, and the muscle fiber relaxes.
_____ D. An electrical impulse causes small vesicles at the end of a motor neuron to release the neurotransmitter acetylcholine (ACh).
_____ E. Calcium binds with the troponin on the actin filament, exposing attachment points.
_____ F. ACh diffuses across the synaptic cleft, where it stimulates receptors in the sarcolemma.
_____ G. Calcium ions are pumped back into the sarcoplasmic reticulum.
_____ H. The myosin heads of the thick filaments grab onto the thin filaments and muscle contraction occurs.
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