Visual System Flashcards
3 layers of the eye
1) Corneosceral coat-cornea-transparent (ant to sclera) Outer
2) Uveal tract- iris and ciliary body anteriorly and vascularized choroid coat posteriourly
3) Retina - Retinanerve cells, their processes, support cells and, on the outside, a layer of pigmented epithelium.
Extra features of the eye
Biconvex lens-elastic for accomodation
2 chambers-aqueous humor-disturbance=glucoma
Vitreal cavity-aq humor and avascular and geltinous due to collagen fibres and hyaluronic acid
Fields and retina
Nasal retina linked with temporal field
Temporal retina linked with nasal field
Retina
More rods than cones
Rod=rhodopsin=ligt-sensitive
Cone=opsin pigments (red/green/blue)
Light hyperpolarises and decrease firing rate
Photoreceptor cell> Info>Bipolar Cell> Retinal ganglion cell
Modified by ass. neurons
Layers of Retina (sup to inf)
Sclera Choroid Pigment cells Cone Rod Cone and rod fibres Horizontal cell Bipolar cell Amacrine cell Interplexiform cell Ganglion cell Light
Retinal Ganglion Cell Receptive Fields
Central-circle
Ring-surround
On centre-ilimuinate centre and iliminate the surround inhibits
Off centre-dark spot in centre activates and darkness in surround inhibits
Point of fixation
Fovea centralis
Reasons for high visual acuity
Thinning of retinal layer
Lack of rods and high conc of cones
Low convergence
Optic nerve
Axons not myelinated in the eye, become M after passing the lamina cribrosa
Myelin formed by olidosendrocytes
Surrounded by meninges
1000000 axons in each ON
Optic nerve crossing is called
Optic chiasma
Objects projected onto the retina are reversed and upside down because of the…
Lens
Nasal retina fibres cross at optic chiasma
Optic tract looks at contralateral visual field
Contralateral visual field
Optic tract, lat geniculate nucleus, optic radiation and visual cortex
Fibres from retina mainly project to
Primary visual cortex
Other areas fibres from retina project to
Pretectal area
