Chapter 2: The First Steps in Vision: From Light to Neural Signals. V1 Flashcards
Wave
An oscillation that travels through a medium by transferring energy from one particle or point to another without causing any permanents displace of the medium.
Photon
A quantum of visible light or other form of electromagnetic radiation demonstrating both particle and wave properties.
Absorb
To take up energy and not transmit it at all
Scatter
To disperse light in an irregular fashion.
Reflect
To redirect something that strikes a surface back towards point of origin
transmit
To convey something from one place to another
Refract
- 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.
- To measure the degree of refraction in a lens/eye.
Cornea
Transparent window into eyeball
Transparent
Allowing light to pass through with no interruption, so that objects on the other side can be clearly seen.
Aqueous Humor
Watery fluid in anterior chamber of eye.
Crystalline Lens
Lens inside eye that enables changing of focus
Pupil
Dark, circular opening at the center of the iris in the eye, where light enters the eye.
Iris
Colored part of eye, consisting of muscular diaphragm surrounding the pupil.
Vitreous humor
Transparent Fluid that fills the vitreous chamber in the posterior part of eye.
Retina
A light-sensitive membrane in the back of the eye that contains rods and cones, which receive an image from the lens and send it to the brain through the optic nerve.
Accommodation
The process by which the eye changes its focus (in which the lens gets fatter as gaze is directed toward nearer objects).
Presbyopia
Old sight. Loss of near vision because of insufficient accommodation.
Cataract
An opacity of the crystalline lens.
Emmetropia
No refractive error because power of eye is perfectly matched to length of eyeball.
Myopia
Nearsightedness, light entering eye is focused in front of retina and distant objects cannot be seen sharply.
Hyperopia
Farsightedness, light entering eye is focused behind the reitna and accommodation is required in order to see near objects clearly.
Astigmatism
Visual defect caused by unequal curving of one or more of the refractive surfaces of the eye, usually cornea.
Transduce
To convert from one form of energy to aother
Fundus
Back layer of retina, what eye doctor sees though scope.
Photoreceptor
A light-sensitive receptor in the retina.
Rod
Photoreceptor specialized for night vision.
Cone
Photoreceptor specialized for daylight vision, fine visual acuity, and color.
Duplex
In reference to retina, consisting of two parts: Rods/cones.
Outer Segment
The part of photoreceptor that contains photopigment molecules.
Inner Segment
The part of photoreceptor that lies between the outer segment and the cell nucleus.
Synaptic Terminal
The location where axons terminate at the synapse for transmission of information by the release of a chemical neurotransmitter.
Chromophore
Light catching part of visual pigments of the retina.
Rhodopsin
Visual pigments found in rods.
Melanopsin
A photopigment that is sensitive to ambient light.
Photoactivation
Activation by light.
Hyperpolarization
Increase in membrane potential such that the inner membrane surface becomes more negetive than the outer membrane surface.
Graded Potential
Electrical Potential that can vary continuously in amplitude.
Eccentricity
The distance between retinal image and the fovea.
Aging-related macular degeneration (AMD)
A disease associated with aging that affects the macula. Destroys sharp central vision. Wet and dry forms.
Macula
Central part of retina that has a high concentration of cones.
Fovea
A small pit, near center of the macula, that contains the highest concentration of cones, no rods. It is the portion of the retina that produces highest visual acuity and serves as the point of fixation.
Scotoma
A blind spot in visual field.
Horizontal Cell
A specialized retinal cell that contacts both photoreceptor and bipolar cells.
Lateral Inhibition
Antagonesitic neural interaction between adjacent regions of the retina.
Amacrine Cell
A retinal cell found in the inner synaptic layer that makes synaptic contacts with bipolar cells, ganglion cells, and other amacrine cells.
Bipolar Cell
A retianl cell that synapses with rods/cones (not both) and with horizontal cells, and then passes signals to ganglion cells
Diffuse bipolar cell
A bipolar retinal cell whose processes are spread out to receive input from multiple cones.
Sensitivity
- Ability to perceive via sense organs.
Visual acuity
A measure of the finest detail that can be resolved by the eyes.
Midget Bipolar Cell
A small bipolar cell in the central retina that receives input from a single cone.
ON bipolar cell
A bipolar cell that responds to an increase in light captured by the cones.
OFF bipolar cell
A bipolar cell that responds to a decrease in light captured by the cones.
Ganglion cell
A retinal cell that receives visual information from photoreceptors via two intermediate neuron types (bipolar cells and amacrine cells) and transmits info to the brain and midbrain.
P ganglion cell
A small ganglion cell that receives excitatory input from the single midget bipolar cells in the central retina and feeds the parvocellular layer of the later genicualte nucleus.
M ganglion cell
A ganglion cell resembling a little umbrella that receives excitatory input from diffuse bipolar cells and feeds the magnocellular layer of the lateral geniculate nucleus.
koniocellular cell
A neuron located between the magnocellular and parvocellular layers of the later geniculate nucleus. Layer is known as koniocellular layer.
Receptive field
The region on the retina in which visual stimuli influence a neurons’s firing rate.
ON-center cell
A cell that depolarizes in response to an increase in light intensity in its receptive-field center.
OFF-center cell
A cell that depolarizes in response to a decrease in light intensity in its receptive-field center.
Filter
Allows passage of some and restricts others
Contrast
Difference in luminance between an object and the background or between lighter and darker parts of same object.
Retinitis Pigmentosa (RP)
A progressive degeneration of retina that affects night vision and peripheral vision. RP is hereditary.
