Action potential in a motor neuron triggers the release of what neurotransmitter?

Action potential in a motor neuron triggers the release of acetylcholine (ACh) neurotransmitter.

Explanation:

Acetylcholine: It is a neurotransmitter released by motor neurons which bind to the receptors end plates of the motor. When an action potential travel down the motor neuron's axon, neurotransmitter release occurs resulting in an influx of calcium and altered permeability of the synaptic terminal membrane.

The Ca2+ ions allow synaptic vesicles to move and bind with the presynaptic membrane which is present on the neuron and released neurotransmitter from the vesicles into the synaptic cleft. Once it's released ACh diffusion occurs across the synaptic cleft to the motor end plate, and binds with ACh receptor. As the neurotransmitter ACh binds, these ions channel open and sodium ions cross the membrane into the muscle cells.

In this phase reduction of voltage inside and outside the cell occurs, which is known as depolarization. When ACh binds to the motor end plate this depolarization is known as end plate potential. Then depolarization spread with the sarcolemma and creating an action potential. This action potential moves the entire cell and creating a wave of depolarization.