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89 Cards in this Set
- Front
- Back
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What is the primary visual pathway?
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retina->optic nerve->optic chiasm->optic tracts->LGN->optic radiations->V1
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When the axons of the ganglion cells exit the retina via the optic nerve, the nasal fibers from each eye cross and terminate in the opposite side of the brain. What is this area of crossing called?
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Optic chiasm
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Axons leaving the optic chiasm form what?
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Optic tracts
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After following along the optic tract, ganglion cell axons next synapse in what?
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Lateral geniculate nucleus (LGN) or body
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The axons that leave the LGN form the optic radiations and then synapse in what?
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Primary visual cortex (or striate cortex or V1)
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What are the 4 segments of the optic nerve?
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Intraocular, intraorbital, intracanalicular, intracranial
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The intraocular segment of the optic nerve can be divided into what?
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Prelaminar and laminar segments, divided by the lamina cribrosa
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Sheaths of astrocytes bundle axons into what?
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Fascicles containing 1000 fibers
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The optic nerve is encased in what?
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3 Meningeal sheets (dura matter, arachnoid, pia matter)
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Which meningeal sheet of the optic nerve is a very tough protective layer?
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Dura matter
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Which meningeal sheet of the optic nerve is a delicate spiderweb like layer? What does it allow the flow of?
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Arachnoid and cerebral spinal fluid (CSF)
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Which meningeal sheet of the optic nerve is loose vascular connective tissue that supplies the nerve and meningeal sheaths?
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Pia matter
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What encases the optic chiasm?
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Meningeal sheets and CSF
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The optic chiasm can be found within what area? This area is common location for what condition?
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The circle of willis and aneurysms
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What is an anastomotic group of anterior and posterior arteries that join the anterior circulation of the internal carotid arteries with the posterior circulation of the basilar artery?
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Circle of willis
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What vessels supply the anterior cranial regions including most of the cerebral hemispheres and orbital and ocular structures?
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Internal carotid arteries
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What vessels supply the posterior regions, including the brain stem, occipital lobes, and inferomedial temporal lobes, thus supplying most of the ocular motor centers and the cortical visual areas?
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Verterbral branches of the basilar artery
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If the circle of willis is complete, what are joined and by what?
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Anterior cerebral arteries are joined by the anterior communicating artery. Each internal carotid artery is joined to the ipsilateral posterior cerebral artery by a posterior communicating artery.
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If the optic chiasm is anterior to the pituitary it is said to be what?
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Prefixed
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If the optic chiasm is posterior to the pituitary it is said to be what?
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Postfixed
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What four locations are contacted by fibers that peel off the optic tract?
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Pretectal nucleus, superchiasmatic nucleus, superior colliculus, nucleus of the optic tract
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What reflex is involved with pretectal nucleus?
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Pupillomotor
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What is involved with the optic tract fibers that project to the superchiasmatic nucleus within the hypothalamus?
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Circadian rhythm
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What is involved with the optic tract fibers that project to the superior colliculus ?
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Reflexive gaze movements
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What is involved with the optic fibers that project to the nucleus of the optic tract?
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Optokinetic nystagmus (OKN)
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Visual information is processed in what?
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Lateral geniculate nucleus of the thalamus
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What are the three cell types of LGN and how many layers of each?
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Magnocellular (large sized cells & 2 layers), Parvocellular (medium sized cells & 4 layers), Koniocellular (small sized cells & 6 layers)
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What is the number and location of the primary visual cortex?
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(Broadman area 17, V1, or striate cortex) and located almost entirely on the medial surface of the occipital lobe.
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The calcarine fissure extends from what to what?
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Parieto occipital sulcus to the posterior pole.
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Calcarine fissure divides the visual cortex how?
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Upper portion (cuneus gyrus) and lower portion (lingual gyrus)
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Outer retina receives nutrition from what?
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Choroid
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Inner retina receives nutrition from what?
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Central retinal artery
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Optic disc supplied by what?
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Circle of zinn (via the short ciliary arteries) and the peripapillary vessels
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Optic nerve supplied by what?
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Vessels in pia
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Intraorbital segment is supplied by what?
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Branches from the ophthalmic artery
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Intracranial segment is supplied by what?
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Branches from the ophthalmic anterior cerebral, anterior communicating, and internal carotid arteries
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Optic chiasm is supplied by what?
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Arterioles from the circle of willis
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Superior network is supplied by what?
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Anterior cerebral and anterior communicating arteries
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Inferior network is supplied by what?
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Internal carotid, posterior cerebral, and posterior communicating arteries
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What supplies the optic tract, along with small branches from the middle cerebral artery?
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Anterior choroidal artery
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The LGN receives supply from what?
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Anterior choroidal arter, lateral choroidal, and posterior choroidal arteries
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Anterior radiations are supplied by what?
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Anterior choroidal & middle cererbral artery
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Posterior radiations are supplied by what?
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Posterior cerebral artery
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Striate cortex is supplied by what?
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Calcarine branch of the posterior cerebral artery, supplemented by the posterior temporal branch of the posterior cerebral artery and/or the occipital branch of the middle cerebral artery
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What term is used to describe the entire visible area?
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Visual field
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Retinal ganglion cell axons form a characteristic pattern. A large group of fibers that course from the macula to the optic disc is the papillomacular bundle. The fibers split superior and inferior where?
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At the horizontal retinal raphe
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In the optic chiasm, approximately how many of the nasal fibers cross (decussate)?
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53%
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In the LGN, superior retinal ganglion cells terminate where?
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Medial within the LGN
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In the LGN, inferior retinal
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Lateral within the LGN
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There is medial to lateral retinal ganglion cell organization in the LGN, creating a complete what?
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Retinotopic map in each layer of the LGN
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In the LGN, layers 1&2 are what? Layers 4-6 are what?
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Magnocellular layers and parvocellular layers
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For magnocellular layers of LGN, layer one receives what and layer 2 receives what?
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Layer 1: input from the contralateral eye
Layer 2: input from ipsilateral eye |
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For parvocellular layers, layers 3 & 5 are what and 4& 6 are what?
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3 & 5: ipsilateral
4 & 6: contralateral |
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Fibers leaving the lateral aspect of the LGN loop around the tip of the lateral ventricle and forms what?
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Meyer's loop
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Meyer's loop represents fibers from where and what part of the visual field?
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Fibers from the inferior retina and the upper visual field
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The cuneus gyrus represents what part of the visual field?
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The lower visual field
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The lingual gyrus represents what part of the visual field?
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The upper visual field
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Superior radiations of striate cortex terminate where?
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Cuneus gyrus
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Inferior radiations of striate cortex terminate where?
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Lingual gyrus
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What is the portion of the visual field that is only seen by one eye, primarily because the nose is obstructing the field of view?
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Temporal crescent
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Concerning the field of view, what occurs where the optic nerve exits the retina?
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Physiological blind spot
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In the optic chiasm, fibers hemi-decussate and afterwards the brain receives information about the visual world from only the opposite side of visual space for both eyes. Also know as what?
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Contralateral hemifield
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A field defect that affects vision in just one eye must be where?
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Anterior to optic chiasm
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What is a loss of vision in the same visual field of both eyes?
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Homonymous hemianopsia
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Where must the damage occur in a loss of vision in the same visual field of both eyes?
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Posterior to the optic chiasm
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What is the result of a lesion of the choroid (or outer retina) in the superior nasal retina?
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Scotoma in the inferior temporal visual field
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In glaucoma, nerve fiber layer can be damaged. If the temporal retinal fibers are affected, an arcuate defect can be produced that curves around the point of fixation from the blind spot to termination at the horizontal nasal meridian. The abrupt edge at the horizontal meridian is called what?
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Nasal step
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The nasal step results from what?
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Configuration of fibers at the temporal retinal raphe.
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What field defects usually show up with a lesion of the chiasm?
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Bitemporal or binasal defects or bitemporal hemianopsia
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Most common cause of a bitemporal field defect is what?
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Pituitary gland tumor
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The defects in a homonymous field are what if the two defects are similarly shaped and what if the defect shapes are dissimilar?
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Congruent and incongruent
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Involvement of both lateral sides of the chiasm, producing a binasal defect, might be caused by what?
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Aneurysm of the internal carotid artery that impinges on the chiasm and displaces it against the other internal carotid artery
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A lesion involving the optic tract eventually will produce optic nerve atrophy which becomes evident as what?
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Optic disc pallor-the presentation of glial in replacement for the optic nerve fibers in optic disc
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A lesion of the optic radiations causes what kind of field defect?
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Contralateral homonymous field defect and because the fibers are so spread out, the defect often affects only one quadrant.
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If a lesion of the temporal lobe involves Meyer's loop, what field defect will result?
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Superior quadrant field defect.
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Parietal lobe lesions cause what kind of field defect?
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Inferior field defects
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Complete interruption of left optic nerve results in what?
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Complete loss of visual field for left eye.
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Interruption in midline of optic chiasm results in what?
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Bitemporal hemianopia
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Interruption in right optic nerve at junction with chiasm results in what?
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Complete loss of visual field for right eye and superior temporal loss in field for left eye.
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Interruption in left optic tract causes what?
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Incongruent right homonymous hemianopia
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Complete interruption in right optic tract, LGN, or optic radiations results in what?
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Total left homonymous hemianopia
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Interruption in left optic radiations involving Meyer's loop causes what?
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Incongruent right homonymous hemianopia
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Interruption in optic radiations in left parietal lobe causes what?
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Incongruent right homonymous hemianopia
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Interruption of all left optic radiations results in what?
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Total right homonymous hemianopia
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Interruption of fibers in left anterior striate cortex results in what?
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Right homnymous hemianopia with macular sparing.
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Interruption of fibers in right striate cortex result in what?
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Left homonymous hemianopia with macular and temporal crescent sparing
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Interruption of fibers in right posterior striate cortex results in what?
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Left macular homonymous hemianopia
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Interruption of fibers in right anterior striate cortex results in what?
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Left temporal crescent loss
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What occurs when an area of central vision remains within a homonymous field defect?
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Macular sparing
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