Gray vs white rami communicans

 

Gray vs  white rami communicans

White and gray rami communicans connect the sympathetic ganglia to the spinal nerves.

They are associated with the sympathetic nervous system, which is part of the autonomic nervous system responsible for the body's fight or flight response.

White Rami Communicans:

It is myelinated so it looks white.

They situate away from the spinal cord, just lateral to gray rami communicans

They are only attached with the thoracic and upper lumbar spinal nerves.  

They contain preganglionic sympathetic fibers which is the axon of pre-ganglionic neuron located in the lateral horn of spinal cord.

This pre-ganglionic sympathetic fibers passage following pathway:

 lateral horn of spinal cord, ventral root of spinal nerve, trunk of spinal nerve, white rami communicans and synapse with sympathetic ganglion

The pre-ganglionic sympathetic fibers of white rami communicants may synapse with post ganglionic neuron at the same level , or it may ascend or descend and synapse with post ganglionic neuron.

Gray Rami Communicans:

It is un-myelinated so it looks gray .

They are situated near the spinal cord, just medial to the white rami communicants

 They are attached with all spinal nerves of spinal cord

They contain post-ganglionic sympathetic fibers which is the axons of post -ganglionic neuron located within the sympathetic ganglion  

Pathway of post ganglionic fibres

Sympathetic ganglion , gray rami communicans, trunk of spinal nerve, distributed by ventral and dorsal rami of spinal nerves and reach to the target organ (sweat gland, blood vessels etc )  

White rami communicans	Gray rami communicans
It conveys pre-ganglion sympathetic fibers	It conveys post-ganglion sympathetic fibers
Whitish in colour	Grey in colour
It contain myelinated nerve fibres	It contains unmyelinated nerve fibers
It is situated away from the spinal cord	It is situated near to the spinal cord
It is only attached with thoracic and lumbar spinal nerves	It is attached with all spinal nerves
Through white rami communicans pre-ganglionic fibers enter into the sympathetic ganglia	Through gray rami communicans post-ganglionic fibers leave the sympathetic ganglia