Question

The cessation of stimulation at the NMJ following release of the neurotransmitter, Acetylcholine (ACh) occurs by which of the following?
A) re-uptake at the synaptic knobs
B) enzymatic action of Acetylcholinesterase
C) diffusion from the synaptic cleft
D) none of the above
E) A, B and C are correct

Answer 1

Answer:

The correct answer will be option B- enzymatic action of Acetylcholinesterase.

Explanation:

At the neuromuscular junction, the neurotransmitter acetylcholine is released which then binds to the receptor in motor-end plate causes depolarization of the membrane responsible for the release of Ca⁺² ions. These Ca⁺² ions control the contraction of the muscle by binding to troponin.

This mechanism of muscle contraction is blocked after the breakdown of the acetylcholine by the "enzyme acetylcholinesterase" which leads to the closure of the Na⁺ ion-channels. The closure of these channels slows down the depolarization in muscle fiber and thus blocks the pathway which leads to muscle relaxation.

Thus, Option-B is the correct option.