Monday, November 22, 2010

Ocular nerves - Oculomotor, trochlear and Abducens nerve

Ocular nerves are oculomotor, the trochlear and Abducens nerve. Work together in the regulation of eye movements, they are considered as ocular nerves and discussed together.

The (cranial nerve III) oculomotor nerve
Oculomotor nucleus consist of several peer groups of adjacent to average, ventral line to the aqueduct of sylvius in upper colliculi nerve cells. A central group of nerve cells, Edinger-Westphal nucleus innervate pupillary sphincter and ciliary bodies. Situated more dorsally and constitutes the parasympathetic nerve part oculomotor.Nerve cells that mediate the action of eye muscles show definitive topographical representation of back-ventral.El course of nerve fibers previously through the midbrain, medial tot he red core, the substantia nigra and cerebral peduncle. Nerve follows the previous appearance of just mid-brain's pons, between superior cerebellar and later cerebral arteries.

Penetrates the Dura side and prior to the subsequent clinoid process and enters the side wall breast cavernoso.Desde there, enter orbit of supplied and superior orbital fissure lift palpaebrae superioris, inferior oblique and straight top, medial and bottom muscles. The preganglionic parasympathetic fibers from the Edinger-Westphal nucleus passed to ciliary ganglion, whence postganglionic fibers provide pupillary constrictores and ciliary muscles which function in accommodation.

The trochlear nerve (4th cranial nerve)
This is the smallest of the cranial nerves and is situated just prior to the aqueduct in the midbrain immediately above the curve fibres pons.Las and with the aqueduct later and decussate in previous Medullary veil. Penetrates hard posterolateral clinoid later process into the cavernous sinus where is lateral and lower third nerve. On the superior orbital fissure enters orbit to provide superior oblique muscle. This nerve palsy causes weakness movement down and to outside eyes and extorsion (eyeball outward rotation).

Abducens nerve (cranial nerve VI) (Abducent nerve)
This nerve emerges from the bottom of the pons on the fourth floor ventriculo.El nerve follows the brain stem in the pontomedullary junction. It has the longest intracranial course between the cranial nerves and lies between the bridge Pons and the clivus. Drilled in the back between the subsequent clinoid and apex of the petrous bone sellae Dura into the cavernous sinus inferomedial 3rd nerve.Enters orbit through superior orbital fissure to supply the rectus (lateral) external.

Medial longitudinal fasciculus: This fiber tract une 3rd cores, 4, 5, 6, 7, 8, 11 and cranial nerve XII and cervical nerves motor kernels higher.Due to this interconnection isolated eye movements are not posibles.Visual, auditory, sensory, vestibular and other stimuli produces conjugated deviation of eyes and head.

Sympathetic innervation: sympathetic fibers that control the action of oculopupillary originate from the eighth cervical and first thoracic spinal segments.Preganglionic fibers will lower sympathetic ganglia, middle and upper neck.Postganglionic fibres follow the course of the internal carotid artery and travel Division of Ophthalmology fifth nerve in orbit.On the nerves for a long ciliary time, supplying the dilators tarsal muscles pupilar.Los and orbital muscle Muller.

Cortical control: the back of the second and third front convolutions are evolutionary cortical control eye movements conjugados.Un Pontine for lateral eye Center also has been described in the vicinity of the Abducens - the center of gaze of parapontine nerve.

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