Visual System Flashcards
Fibrous layer
Vascular layer
Neural layer of the eye
Slera, cornea
Choroid, ciliary body, iris
Retina
Sclera and cornea
Sclera is tough white part that is piereced by optic nerve and central artery of retina
Cornea is transparent
Ciliary body
Anterior component of middle layer
Produces aqueous humor
Iris
Pigmented muscular layer that have shpincter and dilator muscles
Lens
Change shape via the ciliaris muscle
Path of light throug hthe eye
Cornea Aqueous humor Lens Vitreous body Retina
Neural layer
Retina is posterior and ora serrata is most anterior segment of it
Optic disc
Basically the optic nerve
Where central artery of retina eminate
Papilledema
Swelling of optic disk due to increased pressure
Photoreceptor layer of retina
Photoreceptor cells convert light into APs
Plexiform/neural layer
Interneurons
Bipolar - connect receptor cells to retinal ganglion cells
Horizontal cells - refine electrical signal to make it sharper (lateral inhibtion)
Ganglion cell layer
OUtput cells of retina called the ganglion cells
Rods vs. cones
Rods - good for movement and low levels of light…peripheral part…loss is night blindness
Cones - good for color…legally blind if lose these…higher in the macula and fovea
Why is the fovea the best place for vision
Highest concentraiton of cones
Avascular
Axons bend away so not refracted
On center vs. off center
When light hits middle of on-center, depolarizes
When liht hits periphery of off center, depolarizes
Simple cells
Input derived from multiple ganglion cells
Create columns
Optic radiations
From the LGN of the thalamus to the primary auditory cortex
Besides the LGN, RGC project to
Superior colliculus and pretectal area
Path of pupillary light reflex
Retina Pretectal nuclei of MB Parasympathetic nuclei of oculomotor nerve Ciliary ganglion Pupillary sphincter
Binocular vision
Eliminates the blind spot and gives objects depht
Superior and inferior visual fields
Inferior detected by superior retina
Superior by inferior
Paths of superior and inferior fields
Inferior field passes in superior optic rdiation to the cuneus…parietal lobe
Superior field passes in Myers Loop (lateral optic radiation) to the lingula…temporal lobe
Primary visual cortex orgsnization
Macula and fovea in the most posterior portion
Monocular scotoma
Lesion to a certain part of the retina…will just be one tiny blob
Monocular blindness
Lesion to the optic nerve prechiasmal
Heternymous bilateral hemianopia
Temporal loss in each eye (optic chiasm)
Contralateral homonymous hemianopia
Lesion to the optic tract/LGN…will lose entire contralateral field
Contralateral superior quadrantanopia
Lesion to Myer’s loop
Lose contralateral superior portion of vision
Contralateral inferior quadrantanpia
Lesion to superior optic radiation
Lose contralateral inferior portion of vision
Macular sparing
Lesion of the primary visual cortex that spares the caudal pole
Dorsal and ventral pathways
Dorsal pathway involves parietal occipital areas and oncerns the where of svision
Ventral involves the infratemporal areas and concerns the what of vision
Frontal eye fields
In the cerebral cortex (BA 8)…get input from posterior parietal areas, infratemporal area,s and primary visual cortex
Efferent to gaze and superior colliculus
Saccadic movement
Smooth pursuit
Vestbiuloocular
Vergence
Shift fovea to image rapidly
Keep moving image on fovea
Hold images still during short term head movements….controlled by vestbiuklar
Move eyes in opoostive directions to position image on the fovea
Right way eyes
Lesions of cerebral hemisphere make eyes look away from the side of paraylysis (toward lesion)
Wrong way eys
Increased activity cause it to look toward the side of paralysis (away from lesion)
