Vision Chapter 6 Flashcards
receptors
specialized nerve cells that transduce energy
act as dendrites that eventually induce A.P.’s
Mode specific, only detect a small range of energy levels
receptors
function is to detect EMR emitted by objects
visual systems
nature of visible ight
400-700 nM
functions of vision
- locate figure v. ground
- detect movement (predator/prey)
- detect color (adaptive value of color)
light passes through several layers of the _____ to reach the photoreceptors
retina
do we contain more rods or cons?
Rods: 120 million
COnes: 6 million
light sensitive
rods
color sensitive
- one continuous membrane
cones
found in periphery of retina
rods
found mostly in fovea
cones
Bony pockets in the front of the skull.
orbits
The white tissue of the eye.
Sclera
mucous membranes that line the eyelid and protect the eye
Conjunctiva
Transparent outer covering of the eye that admits light.
cornea
Adjustable opening in the iris that regulates the amount of light that enters the eye.
pupil
iris
Pigmented ring of muscles situated behind the cornea.
Consists of a series of transparent, onion-like layers. Its shape can be changed by contraction of ciliary muscles.
lens
Changes in the thickness of the lens, accomplished by the ciliary muscles, that focus images of near or distant objects on the retina.
accommodation
The neural tissue and photoreceptive cells located on the inner surface of the posterior portion of the eye.
retina
Photoreceptor cells of the retina, sensitive to light of low intensity.
rod
Photoreceptor cells of the retina; maximally sensitive to one of three different wavelengths of light and hence encodes color vision. Works at higher light levels.
cone
Area of retina that mediates the most acute vision. Contains mostly color-sensitive cones.
fovea
Location on the retina where fibers of ganglion cells exit the eye; responsible for the blind spot.
optic disk
in the dark, which channels are open and what is released
Na channels open, glutamate released
consist of opsin and retinal
photopigments
net effect of light on the eyes
light hyperpolarizes the retinal receptor
Cells from retina terminate in LGN layers 1,2
Carry info on contrast and movement (color insensitive)
Carry input from “A” retinal ganglion (Y type) cells
Magnocellular system
Cells from retina terminate in LGN layers 3-6
carry info on fine detail, and R/G color
Carry input from “B” retinal ganglion cells (X type)
Parvocellular system
Cells from retina terminate between major layers in LGN.
carry info on B/Y color
Carry input from bistratified ganglion cells
Koniocellular system
shows circular receptive fields
- : larger for magnocellular than parvocellular
LGN
cells respond to only one eye
Columns for left and right alternate
Ocular dominance
Cells respond to same orientation, adjacent cells are shifted by 10 degrees
Are at right angle to ocular dominance column
Do a 180 degrees in 1 mm
Orientation columns:
large areas of light and dark
low frequency
high frequency
fine details
requirements of color vision
at least 2 photoreceptors
- a way to compare their responses-
- different wavelengths of light
specialized neurons that detect a variety of physical events
sensory receptors
stimuli impinge on the receptors and alter their membrane potentials. This process is known as
sensory transduction
the process by which sensory stimuli are transduced into slow, graded potentials
sensory transduction
a slow, graded electrical potential produced by a receptor cell in response to a physical stimulus
receptor potential
affect the release of neurotransmitters and modify the pattern of firing in neurons
receptor potential
perceived color of light determined by which three dimensions
hue, saturation, brightness
dominant wavelength and one perceptual dimension of color
hue
perceptual dimension of color that corresponds to intensity
brightness
purity of the light being perceived
saturation
provide most visual information about our environment
cones
responsible for daytime vision
cones
the source of vision of the highest sharpness
cones
central region of the retina which mediates our most acute vision and contains only cones
fovea
rods or cones are responsible for color vision - our ability to discriminate light of different wavelengths
cones
which is more sensitive to light rods or cones?
rods
in very dim light we use rod or cone vision
rod
responsible for blind spot due to no receptors being there
optic disk
exit point from the retina of the fibers of the ganglion cells that form the optic nerve
optic disk
photoreceptors communicate with _____ who communicate with ___ whose axons send info to the rest of the brain
bipolar cells, ganglion cells
which two cells do the color-sensitive ganglion cells in the retina contain
red-green and yellow-blue
Ventral stream
Recognizes what an object is and what color it has
- provides visual info about size, shape, color, and texture
Dorsal stream
Re ognizes where an object is located
Prosopagnosia
Inability to recognize faces
Optic flow
The relative movement of the visual elements of your environment
Inability to perceive
Movement
Akinetopsia
Damage to area V4
Abolished color constancy
Damage to V8
Cerebral achromatopsia, Loss of color vision
Where
Is the fusiform
Face area located?
In a region I the medial surface of the exrastriate cortex on the base of the brain
