Editing Sympathetic nervous system (section)

===Organization===
[[File:Gray838.png|thumb|The sympathetic nervous system extends from the thoracic to lumbar [[vertebra]]e and has connections with the thoracic, abdominal, and pelvic plexuses.]]

Sympathetic nerves arise from near the middle of the [[spinal cord]] in the [[intermediolateral nucleus]] of the [[lateral grey column]], beginning at the first [[thoracic]] [[vertebra (anatomy)|vertebra]] of the [[vertebral column]] and are thought to extend to the second or third [[lumbar]] vertebra. Because its cells begin in the thoracolumbar division – the thoracic and lumbar regions of the spinal cord – the sympathetic nervous system is said to have a ''thoracolumbar outflow''. [[Axon]]s of these nerves leave the spinal cord through the [[anterior root of spinal nerve|anterior root]].  They pass near the spinal (sensory) ganglion, where they enter the anterior rami of the spinal nerves. However, unlike somatic innervation, they quickly separate out through [[white rami]] connectors (so called from the shiny white sheaths of [[myelin]] around each axon) that connect to either the paravertebral (which lie near the vertebral column) or prevertebral (which lie near the aortic bifurcation) [[ganglion|ganglia]] extending alongside the spinal column.

To reach target organs and glands, the axons must travel long distances in the body, and, to accomplish this, many axons relay their message to a second cell through [[synaptic transmission]]. The ends of the axons link across a space, the [[synapse]], to the [[dendrites]] of the second cell.  The first cell (the presynaptic cell) sends a [[neurotransmitter]] across the synaptic cleft, where it activates the second cell (the postsynaptic cell). The message is then carried to the final destination.

[[File:Gray799.svg|thumb|Scheme showing structure of a typical [[spinal nerve]]. 1. Somatic efferent. 2. Somatic afferent. 3,4,5. Sympathetic efferent. 6,7. Sympathetic afferent.]]
Presynaptic nerves' axons terminate in either the [[paravertebral ganglia]] or [[prevertebral ganglia]]. There are four different paths an axon can take before reaching its terminal. In all cases, the axon enters the paravertebral ganglion at the level of its originating spinal nerve. After this, it can then either synapse in this ganglion, ascend to a more superior or descend to a more inferior paravertebral ganglion and synapse there, or it can descend to a prevertebral ganglion and synapse there with the postsynaptic cell.<ref>{{cite web |title=Divisions of the autonomic nervous system - sympathetic division pathways |url=https://content.byui.edu/file/a236934c-3c60-4fe9-90aa-d343b3e3a640/1/module10/readings/divisions_nerve_system.html#:~:text=The%20cell%20bodies%20of%20the,and%20enter%20a%20spinal%20nerve. |publisher=[[Brigham Young University–Idaho]] |access-date=31 March 2023 |archive-url=https://web.archive.org/web/20230218104009/https://content.byui.edu/file/a236934c-3c60-4fe9-90aa-d343b3e3a640/1/module10/readings/divisions_nerve_system.html |archive-date=18 February 2023}}</ref>

The postsynaptic cell then goes on to innervate the targeted end effector (i.e. gland, smooth muscle, etc.).  Because paravertebral and prevertebral ganglia are close to the spinal cord, presynaptic neurons are much shorter than their postsynaptic counterparts, which must extend throughout the body to reach their destinations.

A notable exception to the routes mentioned above is the sympathetic innervation of the suprarenal (adrenal) medulla.  In this case, presynaptic neurons pass through paravertebral ganglia, on through prevertebral ganglia and then synapse directly with suprarenal tissue. This tissue consists of cells that have pseudo-neuron like qualities in that when activated by the presynaptic neuron, they will release their neurotransmitter (epinephrine) directly into the bloodstream.

In the sympathetic nervous system and other peripheral nervous system components, these synapses are made at sites called ganglia. The cell that sends its fiber is called a preganglionic cell, while the cell whose fiber leaves the ganglion is called a [[postganglionic]] cell. As mentioned previously, the preganglionic cells of the sympathetic nervous system are located between the first thoracic segment and the third lumbar segments of the spinal cord. Postganglionic cells have their cell bodies in the ganglia and send their axons to target organs or glands.

The ganglia include not just the sympathetic trunks but also the [[cervical ganglia]] ([[superior cervical ganglion|superior]], [[middle cervical ganglion|middle]] and [[inferior cervical ganglion|inferior]]), which send sympathetic nerve fibers to the head and thorax organs, and the [[celiac ganglion|celiac]] and [[mesenteric ganglion (disambiguation)|mesenteric ganglia]]<!--intentional link to DAB page-->, which send sympathetic fibers to the gut.

{{Table of autonomic innervation of organs}}