Visual System Flashcards
cornea
clear protective tissue on top of eye; where light first encounters the eye
iris
(colored part) regulates the size of the pupil or how much light passes into the eye
- Darker spaces → larger pupils to let in more light
- Lighter spaces → smaller pupils to limit light exposure
lens
focuses images via muscular movement; nearby object=muscles tighten and bulge; For distant objects=muscles relax and flatten; (VISUAL ACCOMODATION)
retina
where light must arrive in order to see an image
fovea
center of retina, mostly cones, no rods, region on the eye in which acuity is best
photoreceptors
convert light into visual stimuli; 2 types: rods and cones
rods
Photoreceptors that are sensitive to very low light levels but that are unable to discriminate hues and that have relatively poor acuity; also color-blind: They can distinguish different intensities of light but cannot tell hues apart
cones
Photoreceptors that are able to discriminate hues and that have high acuity. Cones are concentrated in the retina’s fovea and become less frequent in the visual periphery. Often contrasted with rods.
lateral inhibition (process)
ore stimulated cells can inhibit their neighborings more… inhibition lowers firing rate
Not all equally powerful and the more they are activated, the more power they have to inhibit their neighbors; The brain interprets higher firing rates as coming from brighter stimuli
ganglion cells
A type of neuron in the eye, receive their input from the bipolar cells, and then the axons of the ganglion cells gather together to form the optic nerve, carrying information back to the lateral geniculate nucleus.
bipolar cells
A type of neuron in the eye; receive their input from the photoreceptors and transmit their output to the retinal ganglion cells.
optic nerve
bundle of nerve fibers, formed from the retina’s ganglion cells, that carries information from the eyeball to the brain; relay and integrate information to lateral geniculate nucleus (LGN) in the thalamus
lateral geniculate nucleus
important way station in the thalamus that is the first destination for visual information sent from the eyeball to the brain.
edge enhancement
A process created by lateral inhibition in which the neurons in the visual system give exaggerated responses to edges of surfaces
acuity
The ability to see fine detail.
blind spot
the position at which the neural fibers that make up the optic nerve exit the eyeball, no space for rods or cones
mach band
A type of illusion in which one perceives a region to be slightly darker if it is adjacent to a bright region, and also perceives a region to be slightly brighter if it is adjacent to a dark region. This illusion, created by lateral inhibition, contributes to edge enhancement.
