Parasympathetic root of ciliary ganglion
Encyclopedia
The parasympathetic root of ciliary ganglion provides parasympathetic innervation to the ciliary ganglion
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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.
, 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.
). Neither of these muscles is under voluntary control.
Ciliary ganglion
The ciliary ganglion is a parasympathetic ganglion located in the posterior orbit. It measures 1–2 millimeters in diameter and contains approximately 2,500 neurons. Preganglionic axons from the Edinger-Westphal nucleus travel along the oculomotor nerve and form synapses with these cells...
.
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 nucleusEdinger-Westphal nucleus
The Edinger-Westphal nucleus is the accessory parasympathetic cranial nerve nucleus of the oculomotor nerve , supplying the constricting muscles of the iris...
, the parasympathetic motor nucleus associated with the oculomotor nucleus
Oculomotor nucleus
The fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle...
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
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...
(cranial nerve III). The oculomotor nerve passes through the cavernous sinus
Cavernous sinus
The cavernous sinus , within the human head, is a large collection of thin-walled veins creating a cavity bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica.-Contents:...
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
Extraocular muscles
The extraocular muscles are the six muscles that control the movements of the eye . The actions of the extraocular muscles depend on the position of the eye at the time of muscle contraction.-List of muscles:-Importance:...
. 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 (accommodationAccommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
). Neither of these muscles is under voluntary control.
External links
- http://anatomy.med.umich.edu/modules/head_autonomics_module/autonomics_05.html