The sympathetic ganglia, or paravertebral ganglia, are

autonomic ganglia An autonomic ganglion is a cluster of neuron, nerve cell Cell body, bodies (a ganglion) in the autonomic nervous system. The two types are the sympathetic ganglion and the parasympathetic ganglion. References

Autonomic ganglia, Auto ...

of the

sympathetic nervous system The sympathetic nervous system (SNS or SANS, sympathetic autonomic nervous system, to differentiate it from the somatic nervous system) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous sy ...

. 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 that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

. 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 body to the brain 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 head, neck, chest, abdomen, or Vertebral column, spine. Symptoms may include ...

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

. 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 horse anatomy, horses. In tailless primates (e.g. hum ...

, forming the unpaired

ganglion impar The pelvic portion of each sympathetic trunk is situated in front of the sacrum, medial to the anterior sacral foramina. It consists of four or five small sacral ganglia, connected together by interganglionic cords, and continuous above with the ...

. Ganglia within this chain are either cervical, thoracic, lumbar, or sacral. Preganglionic nerves from the

synapse In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...

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. Ther ...

abdominal cavity The abdominal cavity is a large body cavity in humans and many other animals that contain Organ (anatomy), organs. It is a part of the abdominopelvic cavity. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roo ...

, 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 reproduc ...

. There are usually 22–23 pairs of these ganglia: three cervical ganglia, 12 thoracic ganglia (the stellate ganglion (cervicothoracic) is formed from the fusion of the first thoracic ganglion with the inferior cervical ganglion), four

lumbar ganglia The lumbar ganglia are paravertebral ganglia located in the inferior portion of the sympathetic trunk. The lumbar portion of the sympathetic trunk typically has 4 lumbar ganglia. The lumbar splanchnic nerves arise from the Ganglion, ganglia here, ...

, and four or five sacral ganglia. In the area of the

there is a small

. The stellate ganglion is so named due to 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. 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. There is still a myelin sheath present – but in far lower amounts compared to the white ramus communicans. This ramus then enters the spinal nerve and is either sent to its synapsing target, or becomes a visceral branch to enter a plexus such as the superficial or deep cardiac plexuses.

Prevertebral ganglia

Neurons of the prevertebral ganglia, also called collateral ganglia, 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 ...

and innervate organs of the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

and

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

. These include the celiac ganglia, superior mesenteric ganglia, 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