The First Steps in Vision: From Light to Neural Signals Flashcards
inner segment
The part of a photoreceptor that lies between the outer segment and the cell nucleus.
rhodopsin
The visual pigment found in rods.
melanopsin
A photopigment that is sensitive to ambient light.
wave
An oscillation that travels through a medium by transferring energy from one particle or point to another without causing any permanent displacement of the medium.
ON bipolar cell
A bipolar cell that responds to an increase in light captured by the cones.
aqueous humor
The watery fluid in the anterior chamber of the eye.
ON-center cell
A cell that depolarizes in response to an increase in light intensity in its receptive-field center.
sensitivity
(1) The ability to perceive via the sense organs. (2) Extreme responsiveness to radiation, especially to light of a specific wavelength. 3. The ability to respond to transmitted signals.
ganglion cell
A retinal cell that receives visual information from photoreceptors via two intermediate neuron types (bipolar cells and amacrine cells) and transmits information to the brain and midbrain.
P ganglion cell
A small ganglion cell that receives excitatory input from single midget bipolar cells in the central retina and feeds the parvocellular layer of the lateral geniculate nucleus.
pupil
The dark, circular opening at the center of the iris in the eye, where light enters the eye.
diffuse bipolar cell
A bipolar retinal cell whose processes are spread out to receive input from multiple cones.
macula
The central part of the retina that has a high concentration of cones.
scatter
To disperse light in an irregular fashion.
outer segment
The part of a photoreceptor that contains photopigment molecules.
bipolar cell
A retinal cell that synapses with either rods or cones (not both) and with horizontal cells, and then passes the signals on to ganglion cells.
OFF-center cell
A cell that depolarizes in response to a decrease in light intensity in its receptive-field center.
fundus
The back layer of the retina—what the eye doctor sees through an ophthalmoscope.
astigmatism
A visual defect caused by the unequal curving of one or more of the refractive surfaces of the eye, usually the cornea.
graded potential
An electrical potential that can vary continuously in amplitude.
refract
(1) To alter the course of a wave of energy that passes into something from another medium, as water does to light entering it from the air. (2) To measure the degree of refraction in a lens or eye.
chromophore
The light-catching part of the visual pigments of the retina.
cone
A photoreceptor specialized for daylight vision, fine visual acuity, and color.
amacrine cell
A retinal cell found in the inner synaptic layer that makes synaptic contacts with other cells of its kind, as well as bipolar cells and ganglion cells.
myopia
Nearsightedness, a common condition in which light entering the eye is focused in front of the retina and distant objects cannot be seen sharply.