Citation, DOI & article dataCitation: Nour D, Hacking C, Hacking C, et al. Sympathetic nervous system. Reference article, Radiopaedia.org (Accessed on 16 Nov 2022) https://doi.org/10.53347/rID-55532 The sympathetic nervous system (SNS), mediated by the sympathetic chain (trunk) and
ganglia, is a major division of the autonomic nervous system. It is composed of general visceral afferent and efferent axons that allow for involuntary control of bodily functions via the hypothalamus. The overarching function of the sympathetic system is to control the 'fight, fright or
flight' (sympathoadrenal) response. The major preganglionic neurotransmitter in the sympathetic system is norepinephrine (norepinephrine) whereas the major neurotransmitter in the parasympathetic system is acetylcholine (ACh). The major postganglionic neurotransmitter is ACh. On this page:LocationThe sympathetic chain
is external to the spinal column, adjacent to the vertebral bodies and within the perivertebral space. It is comprised of paired, longitudinally arranged, paravertebral sympathetic ganglia linked together by myelinated axons forming the sympathetic trunk. It extends from
the upper neck to the coccyx. Branches from the prevertebral sympathetic ganglia may communicate with paravertebral sympathetic ganglia and/or form a plexus prior to innervating the target organ. Sympathetic chain and ganglia: within the perivertebral space, lateral to the vertebral bodies and anterior to the intervertebral foramen at their respective spinal level
extends from the upper neck to the coccyx 23 paired sympathetic ganglia and 1 unpaired coccygeal sympathetic ganglion (ganglion impar)
OriginThe sympathetic chain and ganglia are comprised of discrete sympathetic ganglia (containing neuronal cell bodies) which communicate with each ganglion via the sympathetic trunk
(containing myelinated axons). cervical: three discrete interconnected ganglia: superior cervical ganglion - elongated cylindrical shape formed by embryologically fused C1 to C4 sympathetic ganglia middle cervical ganglion inferior cervical ganglion which in the majority of people partially fuses with the T1 sympathetic ganglion forming the stellate ganglion- located within the cervicothoracic junction
thorax: T2 to T12 thoracic sympathetic ganglia adjacent to their respective vertebral bodies,
located within the posterior mediastinum abdomen: L1 to L5 lumbar sympathetic ganglia. Located posteriorly to the thoracolumbar fascia within the perivertebral space and posteromedial to the psoas major muscle pelvis:
S1 to S5 sacral sympathetic ganglia. Located on the anterior surface of the sacrum medial to the S1-S4 sacral foramina unpaired coccygeal ganglion - also known as ganglion impar
CourseEfferent pathwayIntra-axial component:
sympathetic nuclei are located within the hypothalamus white matter tracts course to spinal cord segments between T1 and L2 axons synapse at cell bodies within the intermediolateral nucleus of the grey matter lateral horns between T1 and L2 spinal segments
Thoracolumbar outflow: preganglionic myelinated fibers enter the sympathetic ganglia at that spinal level by coursing through the ventral roots, spinal nerve and then
white ramus communicans above T1 and below L2, there are only grey ramus communicans between the spinal nerve and the sympathetic ganglion
Within the paravertebral sympathetic ganglion: preganglionic axons may synapse at their respective ganglia, and then re-enter the spinal nerve as postganglionic axons (via grey ramus communicans) preganglionic axons travel superiorly or
inferiorly along the sympathetic chain that connects each sympathetic ganglia, to innervate different body regions preganglionic axons can leave the sympathetic ganglion directly via sympathetic branches Afferent pathwaycell bodies are located within the dorsal root ganglion axons travel from the target organ to the dorsal root ganglion via the same plexus and nerves that carry efferent fibers -
sympathetic axons can synapse at the intermediolateral nucleus to form a sympathetic reflex arc, or ascend to the hypothalamus within the spinal cord
BranchesBranches of the paravertebral ganglia, prevertebral ganglia and plexus (from superior to inferior): HeadNeck and thoraxsuperior, middle and inferior
cardiac nerves (T1-4): arise from the superior cervical ganglion, middle cervical ganglion, inferior cervical ganglion respectively thoracic cardiac branches: arising from T1-4 sympathetic ganglia which innervate the cardiac plexus Abdomengreater (T5-10) and lesser (T10-11)
splanchnic nerves - arise from the respective thoracic sympathetic ganglia within the posterior mediastinum pierce the crura of the diaphragm to enter the abdominal cavity, join the celiac and superior mesenteric ganglia - communicates with the inferior mesenteric ganglia via the intermesenteric plexus celiac plexus - supplies the liver (via hepatic plexus), gallbladder, bile duct, spleen, pancreas, adrenal glands (via suprarenal plexus), and foregut superior mesenteric plexus - supplies
the midgut (via mesenteric branches) by following the superior mesenteric artery aorticorenal plexus and renal plexus- supplies the kidneys via branches from lesser splanchnic (T10-11) - sympathetics course with the renal arteries to innervate the
kidneys
fibers course with the gonadal arteries to innervate the ovaries/testes
least splanchnic nerve (T12) lumbar splanchnic nerves (L1 and L2) superior hypogastric plexus: formed by descending fibers from the inferior mesenteric ganglion Pelvisright and left inferior hypogastric plexus - formed as the inferior continuation of superior hypogastric plexus -
each courses anterolateral to the sacral promontory sacral splanchnic nerves arising from the S1 to S5 sacral sympathetic ganglia provide branches to the inferior hypogastric plexus
RelationsNeckanterior: scalenus anterior anterolateral:
sternocleidomastoid, carotid sheath (IJV, ICA, vagus nerve) lateral: posterior triangle, fat, brachial plexus posterior: transverse process, vertebral artery Root of the neckposterior: T1 spinal nerve lateral: suprapleural membrane, vertebral artery anterior: carotid sheath, stellate ganglion is located opposite to the neck of the 1st rib, phrenic nerve, scalenus anterior
Thoraxposterior: intercostal nerves, intercostal vessels, anterior: descending thoracic aorta, azygous veins, thoracic duct lateral: parietal pleura Abdomenanterior: inferior vena cava, abdominal aorta posterior: lumbar spinal nerves,
lumbar arteries lateral: psoas major, quadratus lumborum muscles Pelvisneck: ascending pharyngeal and
ascending cervical arteries, thyrocervical trunk and supreme intercostal arteries 4 thorax:
posterior intercostal arteries abdomen: lumbar arteries pelvis: lateral and median sacral
arteries
neck: deep cervical chain lymph nodes thorax:
posterior mediastinal lymph nodes abdomen: para-aortic lymph nodes, cisterna chyli pelvis:
internal iliac lymph nodes
unfused T1 and inferior cervical ganglia (absent stellate ganglion) doubled superior cervical ganglion absent superior cardiac branch (usually on the right) accessory L3 white ramus communicans
celiac plexus block percutaneous splanchnic nerve radiofrequency ablation renal sympathetic denervation stellate ganglion block superior hypogastric plexus block
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What connects the spinal nerves to each sympathetic trunk quizlet?
Connecting the spinal nerves to each sympathetic trunk are rami communicantes. These carry preganglionic axons from the T1-L2 spinal nerves. Preganglionic axons are myelinated so this makes the white rami whitish in color. They are similar to entrance ramps onto a highway.
Where does the sympathetic trunk connect?
The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. The sympathetic trunk lies just lateral to the vertebral bodies for the entire length of the vertebral column.
What part of the nervous system is the sympathetic trunk a part of?
The sympathetic trunk is a fundamental part of the sympathetic nervous system, and part of the autonomic nervous system.
How does the sympathetic trunk connect to the ventral ramus?
EVERY ventral primary ramus is connected to the sympathetic chain by a gray ramus, which carries postsynaptic sympathetic fibers to the VPR. The sympathetic chain exists to carry some of the presynaptic fibers from the T1-L2 levels up to the neck and head and down into the lower abdomen and pelvis.
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