Schematic of the Autonomic Nervous system

3D Model

The autonomic nervous system has two components, sympathetic and parasympathetic, both comprising first order (preganglionic) and second order (postganglonic) neurons. The first order neurons arise in the lateral horn of the spinal cord between spinal cord levels T1-L2 and synapse either in paravertebral or prevertebral ganglia. These 1st order neurons distribute to paravertebral or prevertebral ganglion where they synapse on the 2nd order neuron and distribute peripherally. The parasympathetic system is sometimes called the craniocaudal system since 1st order neurons arise either in the brainstem or spinal cord levels S2-4. The preganlionic neurons distribute to target organs where they synapse with postganglionic neurons located within the target tissue itself, e.g., myenteric plexus.

Concept: S Lozanoff, Illustration: B. Lozanoff, Edit and Upload: J Thompson