Question

After nervous stimulation stops, ACh in the synaptic cleft is prevented from continuing stimulation of contraction by ________?

1) calcium ions returning to the terminal cisternae
2) the tropomyosin blocking the myosin once full contraction is achieved
3) acetylcholinesterase destroying the ACh
4) the action potential stopped going down the overloaded T tubules

Answer 1

Acetylcholinesterase destroys ACh in the synaptic cleft to prevent ongoing muscle contraction following nervous stimulation.

Step-by-step explanation:

After nervous stimulation stops, acetylcholinesterase is responsible for preventing continued stimulation of contraction by destroying the ACh (acetylcholine) in the synaptic cleft. This enzyme rapidly breaks down the acetylcholine, thus halting its action on the muscle fiber and allowing the muscle to relax. While calcium ions do return to the terminal cisternae and tropomyosin blocks the myosin binding sites on the actin once contraction is complete, it is the action of acetylcholinesterase which is directly responsible for breaking down acetylcholine and terminating the muscle contraction signal.