Gray ramus communicans

Gray 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.)
Latin	ramus communicans griseus nervi spinalis
Gray's	subject #208 920

Each spinal nerve receives a branch, gray ramus communicans, from the adjacent ganglion of the sympathetic trunk.

They contain postganglionic sympathetic fibers.

Function (overview)

After signals are carried from the spinal cord to a ganglion through the ventral ramus, they synapse within the ganglion. Post-ganglionic fibres then carry them to the end organs they innervate. Ganglionic influence can be specifically targeted to end organs as well as becoming part of a summating systemic response. If the response is the whole body response, as in sympathetic fight or flight, the signals are distributed to other spinal nerves by way of gray rami which serve as conduits between the spinal nerves.

Specific Functions in the ANS

Some Cervical ganglia and Thoracic ganglia send gray rami communicantes directly to the heart.

Thoracic ganglia send grey rami communicantes to their adjacent body wall. They supply blood vessels, sweat glands, and arrectores pilorum muscles.

Lumbar ganglia have grey rami communicantes that rejoin the appropriate spinal nerves to supply the abdominal wall and lower limbs.

The pelvic ganglia form grey rami communicantes whose lateral (postganglionic) branches supply the pelvic wall and lower limb.

See also

• White ramus communicans

References

Wilson-Pauwels, Linda; Stewart, Patricia A.; Akesson, Elizabeth J. (January 1997). Autonomic Nerves. Canada: B. C. Decker, Inc. pp. 71–104. ISBN 978-1-55009-030-7. 

Additional images

• 

  Deep and superficial dissection of the lumbar plexus.

• 

  Thoracic portion of the sympathetic trunk.

External links

• gray+rami+communicantes at eMedicine Dictionary
• Atlas of anatomy at UMich n3a6p1 - "Autonomic Connections of the Spinal Cord"
• Overview and diagram

This article incorporates text from a public domain edition of Gray's Anatomy.