A Neuromuscular Junction (Step-by-Step)

1 Action potentials flow along the axon of a motor neuron to a neuromuscular junction, where an axon terminal forms a synapse with a muscle fiber.

2 The axon terminal stores neurotransmitter ( green) inside synaptic vesicles.

3 The arrival of an action potential at an axon terminal causes calcium ions (Ca++) to enter the neuron.

4 The influx of Ca++ causes exocytosis of  synaptic vesicles, so neurotransmitter is released into the  synaptic cleft.

5 The plasma membrane of the post-synaptic cell has receptors that bind neurotransmitter.

6 Binding of neurotransmitter opens a channel through the receptor, allowing ions to flow into the postsynaptic cell.