Preganglionic sympathetic neurons and postganglionic sympathetic neurons synapse at the ______ parasympathetic ganglion autonomic plexus sympathetic ganglion dorsal root ganglion thoracolumbar spinal cord Solution Sympathetic ganglion. The shorter preganglionic neurons originate from the thoracolumbar region of the spinal cord specially at T1 to L2-L3 and travel to a sympathetic ganglion, often one of the paravertebral ganglia, where they synapse with a post ganglionic neurons extend across most of the body. Preganglionic nerves from the spinal cord synapse at one of the chain ganglia, and the postganglionic fiber extends to an effector organ..