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Sympathetic Division of the Autonomic Nervous System

Q: In the formation of which abdominal autonomic plexus do sympathetic splanchnic nerves participate?

Sympathetic splanchnic nerves participate in forming the celiac plexus (plexus celiac), also known as the solar plexus. It includes the celiac ganglia, aorticorenal ganglia, and superior mesenteric ganglion; the greater and lesser splanchnic nerves enter this plexus, carrying preganglionic sympathetic fibers. Secondary plexuses branch off the celiac plexus to accompany blood vessels and innervate organs.

Pars sympathica systematis nervosi autonomici

For medical students2 min readUpdated 2026-10-10

The sympathetic division of the autonomic nervous system is a complex set of structures responsible for regulating the body's internal environment. Anatomically, it is clearly divided into two main components: the central spinal apparatus and the extensive peripheral network.

Central componentLocated in the lateral horns of the spinal cord (segments C8 to Th12, less commonly L2–L3)

Neuron typeCells of the central component are preganglionic

Axon pathwayProcesses exit as part of the anterior roots of spinal nerves

Sympathetic trunksExtend along the vertebral column from the base of the skull to the coccyx

Central (Spinal) Component

The central link of the sympathetic nervous system is located exclusively within the spinal cord. The main functional unit here consists of sympathetic neurons, which form nuclei in the lateral horns (cornu laterale).

Topographically, this division has a strict segmental organization. The bulk of the neurons lie in the spinal cord segments from the eighth cervical (C8) to the twelfth thoracic (Th12). In some individuals, the lower boundary of these nuclei may extend to the second or third lumbar segment (L2–L3).

From a classification standpoint, these sympathetic neurons are defined as preganglionic. This means their nerve processes (axons) travel to the sympathetic ganglia. To leave the central nervous system, these axons course anteriorly and exit together with motor fibers as part of the anterior roots of the spinal nerves.

Peripheral Component

Once the fibers leave the spinal cord, they become part of the peripheral component of the sympathetic nervous system. This component is an intricate system of pathways and relay stations that provide innervation to internal organs.

The peripheral component includes the following anatomical structures:

paired sympathetic trunks (trunci sympathici);
sympathetic ganglia (ganglia sympathica), where impulse relay occurs;
communicating branches connecting with other nerves;
visceral branches and plexuses leading directly to target organs.

Anatomy of the Sympathetic Trunks

The right and left sympathetic trunks (trunci sympathici) are the main highways of the peripheral division. They appear as two chains running symmetrically on either side of the vertebral column.

Their extent covers virtually the entire body: the trunks begin superiorly at the base of the skull and descend inferiorly through the cervical, thoracic, lumbar, and sacral regions all the way to the coccyx.

An interesting anatomical feature is the termination of these trunks. At their lowest point in the coccygeal region, the right and left sympathetic trunks converge and unite. They fuse into a single unpaired ganglion known as the ganglion impar.

Mnemonic

To remember the lower junction point of the trunks, use the association: the "Imperial ganglion" (ganglion impar) rules at the very bottom, uniting both sides.

Frequently asked questions

What topographic regions does the sympathetic trunk divide into, and how many ganglia does each contain?

The sources explicitly mention the following topographic divisions of the sympathetic trunk and the number of ganglia for some of them:

Cervical region — typically contains three ganglia: ganglion cervicale superius, ganglion cervicale medium, and ganglion cervicothoracicum (stellatum).
Thoracic region — contains 11–12 thoracic ganglia; another source indicates 10–12 pairs of thoracic ganglia.
Lumbar region — mentioned as a division of the sympathetic trunk, though the exact number of its ganglia is not specified in the cited sources.

The right and left sympathetic trunks run along both sides of the vertebral column from the base of the skull to the coccyx and unite in the region of the ganglion impar.

What is the difference between white communicating branches (rami communicantes albi) and gray communicating branches (rami communicantes grisei)?

White and gray communicating branches differ in nerve fiber structure, origin, and direction.

Feature	White communicating branches (rami communicantes albi)	Gray communicating branches (rami communicantes grisei)
Fiber type	Preganglionic myelinated	Postganglionic unmyelinated
Origin	From spinal nerves Th1–L2	From all sympathetic trunk ganglia
Direction	Toward the sympathetic trunk ganglia	Returning to spinal nerves

Which nerves arise from the cervical sympathetic ganglia to supply the heart?

Cardiac nerves arise from the cervical sympathetic ganglia and pass to the heart. They carry postganglionic sympathetic fibers originating from the cervical and upper thoracic ganglia. These nerves travel to the organ and take direct part in forming the cardiac plexus (plexus cardiacus), providing sympathetic innervation to the heart alongside parasympathetic fibers of the vagus nerve.

Into what two groups are the peripheral sympathetic ganglia divided based on their location?

Based on their location, peripheral sympathetic ganglia are divided into two main groups:

Paravertebral ganglia — form the chain of the paired sympathetic trunk (truncus sympathicus) located on both sides of the spine.
Prevertebral ganglia — located in the abdominal cavity and integrated into sympathetic autonomic plexuses (e.g., the celiac plexus).

Intramural ganglia are less characteristic of the sympathetic nervous system.

Which splanchnic nerves are formed from branches of the thoracic sympathetic trunk?

Two main splanchnic nerves are formed from the branches of the thoracic sympathetic trunk:

Greater splanchnic nerve (n. splanchnicus major) — arises from the 5th through 9th thoracic ganglia.
Lesser splanchnic nerve (n. splanchnicus minor) — arises from the 10th and 11th thoracic ganglia.

These nerves originate from the lower thoracic ganglia, pass through the crura of the diaphragm, and head toward the celiac plexus ganglia.

In the formation of which abdominal autonomic plexus do sympathetic splanchnic nerves participate?

Sympathetic splanchnic nerves participate in forming the celiac plexus (plexus celiac), also known as the solar plexus. It includes the celiac ganglia, aorticorenal ganglia, and superior mesenteric ganglion; the greater and lesser splanchnic nerves enter this plexus, carrying preganglionic sympathetic fibers. Secondary plexuses branch off the celiac plexus to accompany blood vessels and innervate organs.

In which spinal cord structures are the central sympathetic neurons located?

They are located in the lateral horns (cornu laterale) of the spinal cord, within segments C8 to Th12 (sometimes extending to L2–L3).

How do preganglionic neuron axons leave the spinal cord?

Axons of preganglionic sympathetic neurons exit the spinal cord as part of the anterior roots of the spinal nerves.

What is the ganglion impar?

It is an unpaired sympathetic ganglion located in the coccygeal region where the right and left sympathetic trunks unite.

Go deeper

Detailed study of the cytoarchitecture of the lateral horns of the spinal cord.
Anatomical structure and topography of the sympathetic trunk ganglia.
Classification of the communicating branches of the sympathetic trunk.
Formation and course of visceral nerve plexuses.