Given these events:
1. acetylcholine is broken down into acetic acid and choline
2. acetylcholine diffuses across the synaptic cleft
3. an action potential reaches the terminal branch of the motor neuron
4. acetylcholine combines with a ligand-gated ion channel
5. an action potential is produced on the muscle fiber’s plasma membrane
choose the arrangement that lists the events in the order that occur at a neuromuscular junction.
a. 2,3,4,1,5
b. 3,2,4,5,1
c. 3,4,2,1,5
d. 4,5,2,1,3
e. 5,1,2,4,3

b. 3,2,4,5,1

Explanation:

3. The action potential induces an electrochemical process that causes release of the acetylcholine.

2. Release of acetycholine into synaptic cleft is down an electrochemical gradient, i.e through diffusion and not requiring energy input.

4. Acetylcholine then binds and activates ligand-gated ion channels of the muscle fiber to open up.

5. Sodium ions will flow into the muscle generation an action potential that will culminate into contractions.

1. The enzyme acetylcholinesterase will breakdown any acetycholine not needed in the synaptic cleft.