Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of

a ligand-gated sodium channel.

Explanation:

Let us first fill in the gap in the question above. Note that the capitalized words are the missing words in the question.

"Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of A LIGAND- GATED SODIUM CHANNEL''.

Acetylcholine is a chemical known as neurotransmitter that helps in the regulation of endocrine functions and autonomic nervous system function. Apart from the two functions mentioned above, Acetylcholine also slows the rate at which the heart moves or pump blood.

A ligand-gated sodium channel is a situation in which sodium ion moves into a membrane and potassium ion moves because of the reaction between Acetylcholine react and the receptor.