Vision (183-208) Flashcards
Scotoptic vision
Monochromatic vision produced through the rods in low light.
Photopic vision
Chromatic vision produced through the cones under well-lit conditions.
Dark current
Continuous inflow of Na+ and Ca++ into rods and cones in the dark through cGMP-regulated channels, causing hypo polarization and glutamate release.
Hemidecussation
A partial crossing of optic fibers in the chiasma opticum ensuring that information collected from the same part of the visual field by the two retinas is analyzed in the same hemisphere.
Optical illusion
Distortion of visual perception at the cortical level caused by previous experiences.
Sclera
The outmost, white layer of the eyeball.
Cornea
The frontal, transparent part of the sclera with the highest refracting power.
Conjunctiva
A very sensitive epithelial membrane covering the sclera and cornea and lining the inside of the eyelid.
Iris
The circular, pigmented membrane behind the cornea, perforated by the pupil. Its contraction regulates the amount of light passing into the eye.
Choroid
The middle, vascularized layer of the eyeball, including the iris and the ciliary body (ciliary muscles)
Fovea centralis
A depression in the center of the macula of the retina, the area of the most acute vision where only cones are present.
Blind spot (optic disk)
The spot on the retina where the axons of the ganglion cells and blood vessels penetrate the wall of the eyeball. No receptors are found here.
Musculus ciliaris
The lens is attached to the ciliary body (ciliary muscles) in the eye. Its contraction is needed for accommodation.
Glaucoma
An eye disease caused by an excessive intracular pressure due to a disturbance in the production and reabsorption of the aqueous humor.
Cataract
An eye disease caused by the opacity of the lens.
Presbiopia
In elderly people the lens looses its flexibility, this accommodation is no longer possible for short distances. Is corrected by reading glasses.
Cis-retinal
An organic compound derived from vitamin A. In visual pigments it absorbed the energy of photons.
Transducin
G-protein in rodes and cones, activated by the photopigment during light detection.
Rhodopsin
Photopigment in the rods.
Opsin
The protein part of the photopigment.
Horizontal cell
Inhibitory interneuron in the retina that connects receptor cells.
Amacrin cell
An interneuron in the retina that establishes horizontal connections mostly close to the ganglion cells.
Melanopsin
Photopigment contained by the W ganglion cells.
M ganglion cell
A ganglion cell projecting to the magnocellular layer of the corpus geniculatum laterale
P ganglion cell
A ganglion cell projecting to the parvocellular layer of the corpus geniculatum laterale.
Color blindness
Disturbance of color vision causes in most cases by a mutation in the genes coding for the photopigments The most common form is red/green color blindness.
