the receptive surface inside the eye that contains photoreceptors and other neurons
transduction
the conversion of one form of energy to another
cornea
the transparent outer layer of the eye, whose curvature is fixed. bends light rays and is primarily responsible for forming the image on the retina
refraction
the bending of light rays by a change in the density of a medium, such as the cornea and lens of the eye
lens
a structure in the eye that helps focus an image on the retina
ciliary muscle
one of the muscles that control the shape of the lens inside the eye, focusing an image on the retina
accommodation
the process by which the ciliary muscles adjust the lens to bring nearby objects into focus
myopia
nearsightedness; the inability to focus the retinal image of objects that are far away
extraocular muscle
one of the muscles attached to the eyeball that controls its position and movements
photoreceptor
a neural cell in the retina that responds to light
rod
a photoreceptor cell in the retina that is most active at low levels of light
cone
any of several classes of photoreceptor cells in the retina that respond to color vision
bipolar cell
an interneuron in the retina that receives information from rods and cones and passes the information to retinal ganglion cells
ganglion cell
any of a class of cells in the retina whose axons form the optic nerve
horizontal cell
a specialized retinal cell that contacts both photo receptors and bipolar cells
amacrine cell
s specialized retinal cell that contacts both bipolar cells and ganglion cells and is especially significant in inhibitory interactions within the retina
scotopic system
a system in the retina that operates at low levels of light and involves the rods
convergence
the phenomenon of neural connections in which many cells send signals to a single cell
photopic system
a system in the retina that operates at high levels of light,, shows sensitivity to color, and involves the cones
rhodopsin
the photopigment in rods that responds to light
pupil
the opening, formed by the iris, that allows light to enter the eye
iris
the circular structure of the eye that provides an opening to form the pupil
range fractionation
the means by which sensory systems cover a wide range of intensity values, as each sensory cell specializes in just one part of the overall range of intensities
visual field
the whole area that you can see without moving your head or eyes
visual acuity
sharpness of vision
fovea
the central portion of the retina, which is packed with the highest density of photoreceptors and is the center of our gaze
optic disc
the region of the retina that is devoid of photoreceptors because ganglion cell axons and blood vessels exit the eye there
blind spot
the portion of the visual field from which light falls on the optic disc
occipital cortex
the cortex of the occipital lobe of the brain, corresponding to the visual area of the cortex
optic tract
the axons of retinal ganglion cells after they have passes the optic chiasm. most of these axons termiante in the lateral geniculate nucleus
lateral geniculate nucleus
the part of the thalamus that receives information form the optic tract and sends it to visual areas in the occipital cortex
optic radiation
axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex
primary visual cortex
aka V1, striate cortex, or area 17. the region of the occipital cortex where most visual information first arrives
binocular
referring to two-eyed processes
extrastriate cortex
visual cortex outside of the primary visual (striate) cortex
topographic organization
a mapping that preserves the point-to-point correspondence between neighboring parts of space
scotoma
a region of blindness within the visual fields caused by injury to the visual pathway or brain
blindsight
the paradoxical phenomenon whereby within a scotoma, a person cannot consciously perceive visual cues but may still be able to make some visual discrimination
receptive field
the stimulus region and features that affect the activity of a cell in a sensory system
on-center bipolar cell
a retinal bipolar cell that is excited by light in the center of its receptive field