So the pre ganglionic neuron begins either in a spinal cord or in the brain. It then carries our electrical signal via a long axon to our synapse that uses acetylcholine. And then the signal is passed down to this one and at this location it uses our acetylcholine once again. So the major difference between our sympathetic and the parasympathetic is in the parasympathetic, both synapses use acetylcholine. In this case, only the pre uses our acetylcholine. The post uses epinephrine.