Which of the following events occurs in a muscle that is relaxing?

Question

Quizplus · Accepted Answer

AChE (acetylcholinesterase) is present in the synaptic cleft during muscle relaxation, which degrades any remaining acetylcholine and stops the stimulation of the muscle fiber.

Answer: C 
 Released calcium ions are present during muscle relaxation, but their concentration decreases as they move back into the sarcoplasmic reticulum due to active transport pumps.

Answer: E 
 Hydrolysis of ATP occurs during relaxation, as the myosin heads use ATP to detach from the active sites on the thin filaments and return to their original conformation.  A is incorrect because muscle fibers do not shorten during relaxation, D is incorrect because myosin cannot bind to active sites during relaxation.

Which of the Following Events Occurs in a Muscle That