This is a chemical process, the result of a chemical neurotransmitter. This is the propagation of the action potential itself along the membrane of the axon. What you learned about the neuromuscular junction is mostly applicable here as well. Instead, small local potentials are produced which must add together in summation to produce an action potential. Although Ach is a common neurotransmitter, there are many others and the exact effect at the synapse depends on the neurotransmitter involved.
Neurotransmitters can be excitatory or inhibitory .
The result might be to turn off the next neuron rather than to produce an action potential. The basic steps of synaptic transmission are the same as described at the neuromuscular junction. The diagram looks very similar too. But there are some important differences. Refresh your memory about membrane polarity and resting membrane potential .