Parasympathetic root of ciliary ganglion

Infobox Nerve
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Latin = ramus parasympathica ganglii ciliaris
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Caption = Pathways in the Ciliary Ganglion. Green = parasympathetic; Red = sympathetic; Blue = sensory


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DorlandsPre = r_02
DorlandsSuf = 12687938
The parasympathetic root of ciliary ganglion provides parasympathetic innervation to the ciliary ganglion.

The ciliary ganglion is a "parasympathetic" ganglion. Incoming parasympathetic nerve fibers form synapses with the dendrites of nerve cells within the ganglion. However, the ciliary ganglion is not simply a relay station connecting "preganglionic" to "postganglionic" nerve fibers. There are roughly twice as many incoming parasympathetic fibers as outgoing parasympathetic fibers. Neural processing occurs as incoming signals "converge" onto target neurons.

Presynaptic

"Presynaptic" parasympathetic fibers originate in the Edinger-Westphal nucleus, the parasympathetic motor nucleus associated with the oculomotor nucleus in the brainstem. Axons from the Edinger-Westphal nucleus and the oculomotor nucleus run together in the brainstem and exit together as the "oculomotor nerve" (cranial nerve III). The oculomotor nerve passes through the cavernous sinus and enters the orbit through the "superior orbital fissure". It divides into branches that innervate the levator palpebrae superioris and four of the six extraocular muscles. Parasympathetic fibers initially run in the "inferior division" of the oculomotor nerve. They exit as one or two short “motor roots” that synapse in the ciliary ganglion.

Postsynaptic

"Postsynaptic" parasympathetic fibers leave the ciliary ganglion in multiple (six to ten) short ciliary nerves. These nerves enter the posterior aspect of the eyeball to innervate the sphincter pupillae and ciliaris muscles. The "sphincter pupillae" constricts the iris. The "ciliaris" muscle changes the shape of the lens, allowing the eye to focus on nearby objects (accommodation). Neither of these muscles is under voluntary control.

External links

* http://anatomy.med.umich.edu/modules/head_autonomics_module/autonomics_05.html