Optic tract: Definition from Answers.com

Brain: Optic tract

The left optic nerve and the optic tracts.
Latin	tractus opticus
Gray's	subject #189 814
Part of	Visual system
NeuroNames	hier-443
NeuroLex ID	birnlex_1684

The optic tract is a part of the visual system in the brain.

It is a continuation of the optic nerve and runs from the optic chiasm (where half of the information from each eye crosses sides, and half stays on the same side) to the lateral geniculate nucleus.

Right vs. left

The relationships of the retinal fibers to the optic tracts are as follows:

optic tract	temporal retinal fibers	nasal retinal fiber
right optic tract	from the right eye	from the left eye
left optic tract	from the left eye	from the right eye

Pathology

A lesion in the left optic tract will cause right-sided homonomous hemianopsia.

Additional images

Diagram of hippocampus	Schematic diagram of the primate lateral geniculate nucleus.	Superficial dissection of brain-stem. Ventral view.	Coronal section of brain through intermediate mass of third ventricle.
Hind- and mid-brains; postero-lateral view.	Scheme showing central connections of the optic nerves and optic tracts.	Base of brain.	Section of brain showing upper surface of temporal lobe.
Dissection showing the course of the cerebrospinal fibers.	Human brainstem anterior view

v • d • e Sensory system: Visual system and eye movement

Vision	Retina → Optic nerve → Optic chiasm → Optic tract → Lateral geniculate nucleus → Optic radiation → Visual cortex (Cuneus, Lingual gyrus) → Blobs

Tracking	Smooth pursuit: Parietal lobe · Occipital lobe Saccade: Frontal eye fields Physiologic nystagmus → Fixation reflex → PPRF

Horizontal gaze	Abducens nucleus → PPRF → MLF → Oculomotor nucleus → Medial rectus muscle

Vertical gaze	Rostral interstitial nucleus → Oculomotor nucleus, Trochlear nucleus → Muscles of orbit

Pupillary dilation	Ciliospinal center → Superior cervical ganglion → Long ciliary nerves → Iris dilator muscle

Pupillary light reflex (constriction)	Retina → Optic nerve → Optic chiasm → Optic tract → Pretectum → Edinger-Westphal nucleus → Oculomotor nerve → Ciliary ganglion → Short ciliary nerves → Iris sphincter muscle

Accommodation	Retina → Optic nerve → Optic chiasm → Optic tract → Visual cortex → Brodmann area 19 → Pretectum → Edinger-Westphal nucleus → Short ciliary nerves → Ciliary ganglion → Ciliary muscle

Vestibulo-ocular reflex	Semicircular canal → Vestibulocochlear nerve → Vestibular nuclei → Medial rectus muscle

Circadian rhythm	Retina → Hypothalamus (Suprachiasmatic nucleus)

v • d • e Nervous system: Sensory systems / senses

Special senses	Visual system/sight Auditory system/hearing Chemoreception (Olfactory system/smell • Gustatory system/taste)

Touch	Pain • Heat • Balance • Mechanoreception (Pressure, vibration, proprioception)

Other	Sensory receptor • Equilibrioception

Nerves of head and neck: the cranial nerves and nuclei

olfactory (AON->I)

olfactory bulb · olfactory tract

optic (LGN->II)

optic chiasm · optic tract

oculomotor
(ON, EWN->III)

superior branch (parasympathetic root of ciliary ganglion/ciliary ganglion) · inferior branch

trochlear (TN->IV)

no significant branches

trigeminal
(PSN,TSN,MN,TMN->V)

trigeminal ganglion • ophthalmic • maxillary • mandibular

abducens (AN->VI)

no significant branches

facial (FMN,SN,SSN->VII)

near origin	nervus intermedius • geniculate

inside facial canal	greater petrosal (pterygopalatine ganglion) · nerve to the stapedius · chorda tympani (lingual nerve, submandibular ganglion)

at stylomastoid foramen	posterior auricular · suprahyoid (digastric, stylohyoid) · parotid plexus (temporal, zygomatic, buccal, mandibular, cervical)

vestibulocochlear
(VN, CN->VIII)

cochlear (striae medullares, lateral lemniscus) • vestibular (Scarpa's ganglion)

glossopharyngeal
(NA, ISN, SN->IX)

before jugular fossa	ganglia (superior, inferior)

after jugular fossa	tympanic (tympanic plexus, lesser petrosal, otic ganglion) • stylopharyngeal branch • pharyngeal branches • tonsillar branches • lingual branches • carotid sinus

vagus
(NA, DNVN, SN->X)

before jugular fossa	ganglia (superior, inferior)

after jugular fossa	meningeal branch · auricular branch

neck	pharyngeal branch (pharyngeal plexus) · superior laryngeal (external, internal) · recurrent laryngeal (inferior) · superior cervical cardiac

thorax	inferior cardiac · pulmonary · vagal trunks (anterior, posterior)

abdomen	celiac · renal · hepatic · anterior gastric · posterior gastric

accessory (NA,SAN->XI)

cranial · spinal

hypoglossal (HN->XII)

lingual branches

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