What are the key events that result in synaptic transmission once an action potential arrives at a synapse?

What are the key events that result in synaptic transmission once an action potential arrives at a synapse?

Please write about what leads to an action potential briefly.
Most of the essay should be talking about what happens once the action potential arrives at the synapse.

Use the file I have attached to help you. Please include at least 3 references.
Use APA format and citation style.