Neuroanatomy, White Rami Communicans

Excerpt

The white ramus communicans (pl. white rami communicantes), which is also known as the white communicating branch or the white communicating ramus, contains preganglionic fibers of the sympathetic system. The white ramus communicans is a structure that anteriorly connects the spinal nerve to the sympathetic trunk. All preganglionic sympathetic neurons traverse through a white ramus communicans. Though sympathetic neurons emerge from the spinal cord through the ventral root to enter a white ramus, their courses after that can vary in four different ways. Sympathetic neurons follow the pattern of passing through the white ramus as preganglionic neurons, synapsing onto a ganglion, and then innervating their respective organs as postganglionic neurons. Ultimately, these sympathetic fibers target blood vessels, sweat glands, arrector pili muscles, and visceral organs to elicit a "fight or flight" physiological response.