Ramus communicans

Ramus communicans
Scheme showing structure of a typical spinal nerve. 1. Somatic efferent. 2. Somatic afferent. 3,4,5. Sympathetic efferent. 6,7. Sympathetic afferent.
Diagram of the course and branches of a typical intercostal nerve. (Rami communicantes labeled at center.)
Details
Identifiers
Latin	ramus communicans nervorum spinalium
Dorlands /Elsevier	r_02/12689477
TA	A14.2.00.033
FMA	5874
Anatomical terms of neuroanatomy []

Ramus communicans (plural rami communicantes) is the Latin term used for a nerve which connects two other nerves, and can be translated as "communicating branch".

When used without further definition, it almost always refers to a communicating branch between a spinal nerve and the sympathetic trunk. More specifically, it usually refers to one of the following :

The grey and white rami communicantes are responsible for conveying autonomic signals, specifically for the sympathetic nervous system. Their difference in coloration is caused by differences in myelination of the nerve fibres contained within, i.e. there are more myelinated than unmyelinated fibres in the white rami communicantes while the converse is true for the grey rami communicantes.

The grey rami communicantes exist at every level of the spinal cord and are responsible for carrying postganglionic nerve fibres from the paravertebral ganglia to their destination, and for carrying those preganglionic nerve fibres which enter the paravertebral ganglia but do not synapse.

The white rami communicantes exist only at the levels of the spinal cord where the intermediolateral cell column is present (T1-L2) and are responsible for carrying preganglionic nerve fibres from the spinal cord to the paravertebral ganglia.