Which statement correctly describes the sequence of events in muscle contraction?
A) An impulse triggers the release of acetylcholine (ACh), which diffuses across the synaptic cleft to stimulate the sarcolemma to release ATP. The ATP triggers the actin and myosin filaments to shorten, and muscle contraction occurs.
B) An impulse triggers the release of acetylcholinesterase into the synaptic cleft. This causes calcium ions to be pumped into the T tubules. The calcium allows the myosin heads to latch on to the actin filaments and muscle contraction occurs.
C) An impulse triggers the release of acetylcholine (ACh), which diffuses across the synaptic cleft to stimulate the T tubules to release calcium. The calcium binds with troponin on the actin filaments, which permits the myosin heads to latch on and muscle contraction occurs.
D) An impulse triggers the release of acetylcholine (ACh). This stimulates the sarcolemma, which sends an impulse to the actin and myosin filaments. The myosin heads then latch on to the actin filaments, pulling the Z disks closer together, and muscle contraction occurs.

Question

Quizplus · Accepted Answer

The statement that correctly describes the sequence of events in muscle contraction is when an impulse triggers the release of acetylcholine (ACh), which diffuses across the synaptic cleft to stimulate the T tubules to release calcium. The calcium then binds with troponin on the actin filaments, which permits the myosin heads to latch on and muscle contraction occurs. This is the process of excitation-contraction coupling, which enables the muscle fiber to contract in response to a neural signal. Option A and D are incorrect because the sarcolemma alone doesn't release ATP and doesn't send impulses to the actin and myosin filaments. Option B is incorrect because acetylcholinesterase is an enzyme that breaks down ACh, it doesn't cause calcium to be pumped into the T tubules.

Which Statement Correctly Describes the Sequence of Events in Muscle