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

Neurotransmission

Explanation:

Acetylcholine is an excitatory neurotransmitter that can act on both neuronal synapses and motor plates that send signals to the muscles.

Neurotransmitters are like chemical "messengers" that carry, stimulate and balance signals between neurons and other cells in the body.

Acting on a neuron, acetylcholine opens the cell's sodium and potassium channels, causing the concentrations of these two ions inside and outside the cell to stabilize, depolarizing the membrane.

This depolarization will extend through the neuron and give rise to the nerve impulse.  In motor plates (from neuron to muscle), receptors in muscle fibers recognize acetylcholine as a sign for muscle contraction.

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