Chapter 7: Vision Flashcards
Light travels in straight lines until it encountered the _______, which causes light to bend in a process called _______. As the light enters the eye it is further modified by the _____, which is able to change is shape due to the _______ muscles. This process is called _________ and results in the projection of a focused image on the _______, where the photoreceptors are located.
Cornea Refraction Lens Ciliary Accommodation Retina
Sensory neurons that detect light.
Photoreceptors
2 types of photoreceptors in the retina.
Rods and cones
Rods and cones both release neurotransmitter molecules that control ______ _____, which synapse with them.
Bipolar cells
Bipolar cells connect with _______ _____, whose axons form the optic nerve.
Ganglion cells
The _____ are especially involved in the ________ visual system, which works in dim light and does not give rise to color perception. The _____ are especially involved in the _______ visual system, which requires more light but gives highly detailed vision, including color information in many species.
rods
scotopic
cones
photopic
The visual system responds to changes in light. In rods, light particles are captured by the photopigment ________, causing the photoreceptor to _________ and release less neurotransmitter.
rhodopsin
hyperpolarize
The amount of light entering the eye is governed by the size of the _____ , which may be increased by drugs (such as belladonna, or “beautiful lady”) that block cholinergic transmission in the __________ nervous system.
pupil
parasympathetic
By means of _______, the photoreceptors shift their range of responses to suit the available levels of light.
adaptation
Bipolar cells connect to _______ cells and produce _______ potentials.
Horizontal cells connect to _______ cells and produce _______ potentials.
Amacrine cells connect to _______ and _______ cells and produce potentials.
Ganglion cells connect to ______ cells and produce ______ potentials.
ganglion, graded
receptor, graded
bipolar, ganglion, action
brain, action
In humans, axons from the _____ retina cross over to the opposite side of the brain at the optic ______ . Axons from the _______ retina project to their own side of the brain
nasal
chiasm
temporal
Once they enter the brain, the axons of the retinal ganglion cell are called the optic _____ .
tract
Most axons carrying visual information from the eyes terminate at _____ the of the thalamus: _________ (color) layers and __________
(motion) layers.
LGN
parvocellular
magnocellular
Axons from the LGN form a fiber tract called the optic ______ , which terminate(s) at the ______ visual cortex of the _______ cortex at the back of the brain.
radiations
primary
occipial
V1 communicates with a variety of ________ areas and association areas,
forming two general streams or pathways: the ______ stream or “where”
pathway and the ______ stream or “what” pathway
secondary
dorsal
ventral
The where pathway or ______ stream involves regions of the _______ lobe .
dorsal
parietal
The what pathway or ______ stream involves regions of the _______ lobe .
ventral
temporal
Turning off the light in the center of the receptive fields of ___-center bipolar cells causes the receptor cells to release more neurotransmitter, which _______ the bipolar cells. Turning on the light in the center of the ___-center bipolar cells causes the receptor cells to release less neurotransmitter, which _______ the bipolar cells.
off, depolarizes
on, depolarizes
Bipolar cells release the neurotransmitter _______ , which always depolarizes _______ cells onto which they synapse.
glutamate
ganglion
The receptive field of a ganglion cell and bipolar cell is ________—either on-center/off-surround or off-center/on-surround.
concentric
Analysis of motion of visual objects occurs primarily in cortical area ___.
V5
The three dimensions of the color solid are _______, _______, and _______.
hue, light, and saturation
The hypothesis proposed that the retina contained different receptors for each of three colors (red, green, and blue), acting like labeled lines for color information.
Trichromatic Theory
This theory hypothesized that the perception of color was based on the values of three opposed pairs of colors: blue and yellow, green and red, and black and white.
Opponent-process theory
A specialized retinal cell that contacts both bipolar cells and ganglion cells, and is especially significant in inhibitory interactions within the retina.
amacrine cell
Reduced visual acuity that is not caused by optical or retinal impairments.
amblyopia
An interneuron in the retina that receives information from rods and cones and passes the information to retinal ganglion cells
bipolar cell
One of the muscles that control the shape of the lens inside the eye, focusing an image on the retina.
ciliary muscle
A cell in the visual cortex that responds best to a bar of a particular size and orientation anywhere within a particular area of the visual field.
complex cortical cell
The transparent outer layer of the eye, whose curvature is fixed. It bends light rays and is primarily responsible for forming the image on the retina.
cornea
One of the muscles attached to the eyeball that control its position and movements.
extraocular muscle
The central portion of the retina, which is packed with the highest density of photoreceptors and is the center of our gaze.
fovea
A specialized retinal cell that contacts both receptor cells and bipolar cells.
horizontal cell
The circular structure of the eye that provides an opening to form the pupil.
iris
The part of the thalamus that receives information from the optic tract and sends it to visual areas in the occipital cortex.
lateral geniculate nucleus (LGN)
The phenomenon by which interconnected neurons inhibit their neighbors, producing contrast at the edges of regions.
lateral inhibition
A structure in the eye that helps focus an image on the retina.
lens
Nearsightedness; the inability to focus the retinal image of objects that are far away.
myopia
A retinal bipolar cell that is inhibited by light in the center of its receptive field.
___-center bipolar cell
off-center bipolar cell
A retinal ganglion cell that is activated when light is presented to the periphery, rather than the center, of the cell’s receptive field.
___-center ganglion cell
off-center ganglion cell
Referring to a concentric receptive field in which stimulation of the center inhibits the cell of interest while stimulation of the surround excites it.
___-center/___-surround
off-center/on-surround
A retinal bipolar cell that is excited by light in the center of its receptive field.
___-center bipolar cell
on-center bipolar cell
A retinal ganglion cell that is activated when light is presented to the center, rather than the periphery, of the cell’s receptive field.
___-center ganglion cell
on-center ganglion cell
Referring to a concentric receptive field in which stimulation of the center excites the cell of interest while stimulation of the surround inhibits it.
___-center/___-surround
on-center/off-surround
Spatial disorientation in which the patient is unable to accurately reach for objects using visual guidance.
optic ataxia
The region of the retina that is devoid of receptor cells because ganglion cell axons and blood vessels exit the eyeball there.
optic disc
Axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex.
optic radiation
The axons of retinal ganglion cells after they have passed the optic chiasm; most of these axons terminate in the lateral geniculate nucleus.
optic tract
A system in the retina that operates at high levels of light, shows sensitivity to color, and involves the cones.
photopic system
The opening, formed by the iris, that allows light to enter the eye.
pupil
A system in the retina that operates at low levels of light and involves the rods.
scotopic system
Also called bar detector or edge detector. A cell in the visual cortex that responds best to an edge or a bar that has a particular width, as well as a particular orientation and location in the visual field.
simple cortical cell
The photopigment rhodopsin is composed of ______ and ______.
retinal and opsin
