Sympathetic ganglion

Sympathetic ganglion
Autonomic nervous system innervation, showing the sympathetic (thoracolumbar) and parasympathetic (craniosacral) systems, in red and blue, respectively
Diagram of the course and branches of a typical intercostal nerve. (Sympathetic ganglion visible at center top.)
Details
Identifiers
Latin	ganglion sympathicum
Dorlands /Elsevier	g_02/12385047
TA	A14.2.00.011
FMA	5890
Anatomical terminology []

Sympathetic ganglia are the ganglia of the sympathetic nervous system. They deliver information to the body about stress and impending danger, and are responsible for the familiar fight-or-flight response. They contain approximately 20,000–30,000 nerve cell bodies and are located close to and on either side of the spinal cord in long chains. Sympathetic ganglia are the tissue from which neuroblastoma tumours arise.

The bilaterally symmetric sympathetic chain ganglia, also called the paravertebral ganglia, are located just ventral and lateral to the spinal cord. The chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion. Preganglionic nerves from the spinal cord synapse at one of the chain ganglia, and the postganglionic fiber extends to an effector, a visceral organ in the thoracic cavity, abdominal cavity, or pelvic cavity.

There are usually 22-23 pairs of these ganglia: 3 in the cervical region (cervical ganglia), 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 (so called because of its radiating pattern similar in appearance to a star).

The general rule of interaction of the nerve fibres 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.