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The sympathetic ganglia, or paravertebral ganglia are
autonomic ganglia An autonomic ganglion is a cluster of nerve cell bodies (a ganglion) in the autonomic nervous system. The two types are the sympathetic ganglion The sympathetic ganglia, or paravertebral ganglia are autonomic ganglia, of the sympathetic nervous ...
, of the
sympathetic nervous system The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of th ...
. Ganglia are 20,000 to 30,000 afferent and efferent nerve cell bodies that run along on either side of the
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spin ...
. Afferent nerve cell bodies bring information from the body to the brain and spinal cord, while efferent nerve cell bodies bring information from the brain and spinal cord to the rest of the body. The cell bodies create long sympathetic chains that are on either side of the spinal cord. They also form para- or pre-vertebral ganglia of gross anatomy. The efferent nerve cell bodies bring information from the brain to the body regarding perceptions of danger. This perception of danger can instigate the fight-or-flight response associated with the sympathetic nervous system. The fight-or-flight response is adaptive when there is a real and present danger which can be avoided or diminished through increased sympathetic activity. Sympathetic activity could be increased heart rate, dilated pupils, or sweaty palms, for example. The fight-or-flight response is maladaptive when the danger is imagined, prolonged, or when it lasts after the threat is over. When the intensity or duration of the response is excessive, the individual may meet criteria for a variety of psychological disorders.
Neuroblastoma Neuroblastoma (NB) is a type of cancer that forms in certain types of nerve tissue. It most frequently starts from one of the adrenal glands but can also develop in the neck, chest, abdomen, or spine. Symptoms may include bone pain, a lump in ...
tumors can arise from the sympathetic ganglia tissue.


Structure


Sympathetic chain ganglia

The bilaterally symmetric sympathetic chain ganglia, also called the paravertebral ganglia, are located just ventral and lateral to the
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spin ...
. The chain extends from the upper neck down to the
coccyx The coccyx ( : coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and other ...
, forming the unpaired coccygeal ganglion. Each ganglion within this chain is either cervical, thoracic, lumbar, or sacral. Preganglionic nerves from the
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spin ...
synapse In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses from ...
at one of the chain ganglia, and the postganglionic fiber extends to an effector, a visceral organ in the
thoracic cavity The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. There ...
,
abdominal cavity The abdominal cavity is a large body cavity in humans and many other animals that contains many organs. It is a part of the abdominopelvic cavity. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the t ...
, or
pelvic cavity The pelvic cavity is a body cavity that is bounded by the bones of the pelvis. Its oblique roof is the pelvic inlet (the superior opening of the pelvis). Its lower boundary is the pelvic floor. The pelvic cavity primarily contains the reproduct ...
. There are usually 22–23 pairs of these ganglia: 3 in the cervical region (
cervical ganglia The cervical ganglia are paravertebral ganglia of the sympathetic nervous system. Preganglionic nerves from the thoracic spinal cord enter into the cervical ganglions and synapse with its postganglionic fibers or nerves. The cervical ganglion has ...
), 11 in the thoracic region (note the presence of the stellate cervicothoracic ganglia), 4 in the lumbar region and 4–5 in the sacral region. Throughout human evolution, the first thoracic and inferior cervical ganglia merged - and this resulting ganglion is called the
stellate ganglion The stellate ganglion (or cervicothoracic ganglion) is a sympathetic ganglion formed by the fusion of the inferior cervical ganglion and the first thoracic (superior thoracic sympathetic) ganglion, which exists in 80% of people. Sometimes, the seco ...
(so called because of its radiating pattern similar in appearance to a star). The general rule of interaction of the nerve fibers in the sympathetic nervous system begins at the spinal cord. Here they arise from the thoracolumbar (T1–L2) regions' lateral horn of grey and emerge via the ventral root. They enter their respective spinal nerve (e.g. T5), and thus enter the
white ramus communicans The white ramus communicans (plural: rami communicantes) from Latin ramus (branch) and communicans (communicating) is the preganglionic sympathetic outflow nerve tract from the spinal cord. Each of the thoracic, and the first and second lumbar ner ...
. This myelinated division can then enter the sympathetic chain. Here four options are available to the fibers: (1) they can run up the chain and synapse, (2) they can synapse at the level of entry, (3) they can pass straight through and synapse elsewhere – such as in the case of T5–12 (the splanchnic nerves), or (4) they can enter the chain and descend to synapse. It is this ability to move superiorly and inferiorly along the chain that results in the mass response to the sympathetic nervous system. A preganglionic fibre may synapse to 15–20 postganglionic fibres. The postganglionic neurons extend across most of the body. Upon exiting the sympathetic chain, the fibres enter a less-myelinated
gray ramus communicans Each spinal nerve receives a branch called a gray ramus communicans (plural rami communicantes) from the adjacent paravertebral ganglion of the sympathetic trunk. The gray rami communicantes contain postganglionic nerve fibers of the sympathetic n ...
. There is still a myelin sheath present – just in far lower amounts compared to the white ramus communicans. This ramus then enters the spinal nerve and is sent to its synapsing target, or becomes a visceral branch to enter a plexus (e.g. the superficial or deep cardiac plexuses), or synapses directly onto a target.


Collateral ganglia

Neurons of the collateral ganglia, also called the
prevertebral ganglia Prevertebral ganglia (or collateral ganglia, or preaortic ganglia) lie between the sympathetic ganglia and the target organ. Function Similar to the paravertebral ganglia, the prevertebral ganglia are the nodules where preganglionic neurons syna ...
, receive input from the
splanchnic nerves The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the internal organs), carrying fibers of the autonomic nervous system ( visceral efferent fibers) as well as sensory fibers from the organs ( visceral a ...
and innervate organs of the
abdominal The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
and
pelvic The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...
region. These include the
celiac ganglia The celiac ganglia or coeliac ganglia are two large irregularly shaped masses of nerve tissue in the upper abdomen. Part of the sympathetic subdivision of the autonomic nervous system (ANS), the two celiac ganglia are the largest ganglia in the ...
,
superior mesenteric ganglia The superior mesenteric ganglion is a ganglion in the upper part of the superior mesenteric plexus. It lies close to the origin of the superior mesenteric artery. Structure The superior mesenteric ganglion is the synapsing point for one of the p ...
, and inferior mesenteric ganglia.


Additional images

File:Blausen 0838 Sympathetic Innervation.png, Schematic Illustration of Sympathetic Innervation File:Gray530.png, The thoracic aorta, viewed from the left side. File:Gray799.svg, Scheme showing structure of a typical spinal nerve. File:Gray1111.png, Transverse section of human embryo eight and a half to nine weeks old.


References


External links

* () {{Authority control Sympathetic nervous system