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60 Cards in this Set
- Front
- Back
Sequence of how signal runs
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Eye point
Optic Nerve Optic chiasm LGN Primary visual cortex (area 17) - There also connections to the brain stem for eye movement and connections that control size of the pupil via occulomotor (its parasymp division) - There also connections to preganglionic symp at T1 and then synapse on post ganglionic on superior cervical ganglia |
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- Optic nerve characteristics
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CNS tract, oligodendorocytes for myelination, cannot regenerate
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- Optic chiasm fibers
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½ of fibers (from nasal retina) cross
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- Optic tract fibers
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ipsilateral temporal retinal fibers + contralateral nasal retinal fibers
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- LGN = fibers radiate to
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visual cortex via optic radiations which travel in the same direction and appear as a whiter bundle within the white matter
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2) Dura matter continues as
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the sclera of the eyeball. Because the eyeball is an outgrowth of the CNS.
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Subaracnoid continues as
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the choroid, it provides nutrition for outer portions of the retina.
Choroid gives rise to cilliary body |
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– fovea
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= central vision, highest visual acuity, only cones; peripheral vision has greater sensitivity to light and good for motion detection
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- Bending of light towards fovea
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through cornea and lens (cornea bends the light more)
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- With age, lens does not return to proper (rounder) shape as easily ->
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need glasses to correct vision
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3) Visual axis of eye compose of
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nasal retina
temporal retina |
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nasal retina
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close to nose, contains optic nerve and blind spot
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temporal retina
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Visual axis cant be at the level of the fovea because it would mean optic nerve would be there, and receptors would block the light coming in. That’s why optic nerve is at nasal level.
The retina in the eye is part of CNS. |
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Embryology: Optic cup outer part collapses and becomes
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the pigmented epithelium cells at the back of the retina
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Inner cup gives rise to
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CNS or neural part of retina
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choroid is vascular layer on
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outside of retina
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- Retinal detachement
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occurs between the retinal pigment epithelium and the neural retina (layers of optic cup). Needs to be fixed promptly because metabolic support comes through here
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- Fovea is avascular, axons from fovea have primary route to
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optic disk (as a result, axons from lateral eye must go around fovea implications for retinal problems – a larger portion of the field may be damaged by a smaller lesion because of how axons pile up and avoid the fovea, also plays a role in foveal sparing)
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- Pigment layer is the area we have
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the highest concentration of cones to see detail
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Limbus of the cornea at the level where
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where iris meets the cilliary body there are stem cells for the cornea of the epithelium.
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Ciliary body has zonular fibers that
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connect to the lens. When it contracts it releases the tension of the lens so we can see things up close
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Aqueous humorus, circulates and it goes to anterior chamber of the cornea and it exits through canal of schelemm. When theres high pressure, aqueous humor accumulation can lead to
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glaucoma
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Myoepithelim cells are arranged longitudinally along
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the iris and they are dilator muscles (sympathetic innvervation) and medially will be the circular muscle that acts as a spinther (occulomotor)
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Innervation to the sclera that conveys sensation and pain is
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trigeminal
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Bowmans membrane provides an immune barrier and it doesn’t
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regenerate well upon injury so it leads to a scar
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Stroma has uniform collagen fibers so contributes to
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transparency of cornea and depends on fluid and nutrition that goes through endothelium
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Descements membrane regenerates
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effectively and it ends where it meets the sclera, but Bowman’s does
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No blood vessels on cornea so dependent on
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the endothelium
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Greatest amount of bending the light rays will occur at
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air to cornea interface
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Lens fibers are elongated and progressively lose their cellular constituency and are covered by
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cristalline
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- Cones have 1:1 relationship with
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bipolar cells, retains visual acuity
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- Some ganglion cells have melanopsin
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responds slower than rods and cones, connected to hypothalamus for circadian rhythms and in brainstem for reflexes [ganglion cells themselves act as photoreceptors!]
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R visual hemifield corresponds to
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Nasal retina
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L visual hemifield corresponds to
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temporal retina; info from R visual hemifield -> temporal retina
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Superior visual field info path
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- LGN -> Meyer’s loop -> over lateral ventricle -> lingual gyrus ->lower cortex
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info from inferior visual field
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- LGN -> cortex (no Meyer’s loop) -> cuneate gyrus (above calcarine fissure
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- Direct radiations from dorsal retina
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dorsal cortex gyrus cuncus so cortex sees things upside down
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- Macular info reaches what percentage of retina, LGN and primary visual cortex
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1
33 50 |
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- Occlusion of which artery will destroy primary visual cortex?
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Posterior cerebral artery
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11) Blindspot – on nasal retina, so found in the
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TEMPORAL visual field (opposite). Ganglion cell axons exit and become myelinated in optic nerve
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What kind of cells form the myelin on these axons?
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Oligodendrocytes because it is part of CNS
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at level of LGN, input from each eye is still
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separate not integrated
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Ocular dominance columns
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cells in LGN project to primary visual cotex -> ocular dominance columns (input still separate); each column has preference for different line/angle
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- Lesion of R optic nerve
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blindness in R eye (ipsilateral eye
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- Pituitary tumor compressing optic chiasm
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bitemporal hemianopia (fibers from both nasal visual fields affected)
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- Lesion of R optic tract
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L homonymous hemianopia (contralateral visual field)
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- Tumor in temporal lobe affecting R Meyer’s loop
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pie in the sky = L superior quadrantanopia with foveal sparing
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- Lesion in lingual gyrus of R visual cortex
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pie in the sky = L superior quadrantanopia with foveal sparing
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- Usually get foveal sparing with
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CORTICAL lesions
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analyzes where object is and what direction it is moving in
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- Dorsal upper pathway
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analyzes what object is and what color it is
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- Ventral lower pathway
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inability to recognize faces
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- Vascular accident in ventral R temporal lobe
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- Ganglion cells with melanopsin project to
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hypothalamus and suprachiasmatic nucleus for circadian rhythms, connections may reach T1 -> symp that will dilate pupil
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- Ganglion cells project
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suprachiasmatic nucleus (circadian rhythm), pretectal area, or superior colliculus (important for coordinating movement of eyes and head and accommodation of lens)
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- Edinger-Westphal nucleus
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parasymp component of CN3 ->sphincter papillae and ciliary mm
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Consensual Light Reflex
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when shine a light into eye, pupils of both eyes will constrict
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light into damaged eye does not cause either pupil to constrict, light in normal eye causes both pupils to constrict
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damaged retina/optic nerve
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light in damaged eye causes contralateral pupil to constrict, light in normal eye causes only ipsilateral pupil to constrict
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Damaged CN3
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Visual cortex supplied by
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MCA and PCA
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What part of retina is represented on occipital pole
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fovea
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