Sympathetic neurons are in the thoracolumbar spinal cord . All autonomic preganglionic neurons make synapses with clusters of neurons called ganglia . The spinal cord has grey matter and white matter. The spinal cord has the intermedial lateral cell column which has the origin of sympathetic preganglionic neurons which send axons through ventral root where they synapse on a ganglion. The ganglion are found in a chain of ganglion that is close to spinal cord in paravertebral ganglionic chain.
Sympathetic system has short preganglionics and long post ganglionic axons .
When this axon comes out spinal cord, it goes up and down the chain to synapse on adjacent ganglion so have diffusion effect so one preganglionic neuron can stimulate neuron in multiple ganglion. The Parasympathetic Nervous System Long presynaptic acetylcholine fiber comes off of brain. Short postsynaptic with nicotinic receptor goes to target organ . So the preganglionic neuron is long and the postganglionic neuron is short . The postganglionic neuron is usually on surface of innervated organ .