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 .

The answer is "ligand-gated channel".

Explanation:

The action that is described in the question is an example of a "ligand-gated channel".

The ligand-gated channels are found in the muscles and they are membranes made out of ion-channel proteins which chan be controlled by certain released chemicals into the medium to open them up or closed them and allowing the sodium, potassium or calcium ions to pass through.

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b - the respond is innate and varies over time.

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