study guide chpt 3 Flashcards
define electromagnetic spectrum
covers a wide range of wavelengths and photon energies
-is energy that is produced by electric charges and radiated as waves
UNDERSTAND
the visual spectrum is between 400-700
cornea
shapes and focuses the light
accounts for about 80% of focusing
iris
responsible for controlling the diameter and size of the pupils and the amount of light reaching the pupil
lens
adjusts shape for object distance, accounts for the other 20%.
ciliary muscles
permit the lens to change its shape in order to focus on near or distant objects
aqueous humor
fluid nourishes the cornea and the lens and gives the eye it’s shape
vitreous humor
clear gelatinous substance that fills the eyeball between the retina and the lens
retina
a light-sensitive layer at the back of the eye that covers about 65 percent of its interior surface
fovea
the absolute center of vision
-center area of the retina; covered in cones, located in the line of sight
optic nerve
Either of the second pair of cranial nerves, which carry sensory information relating to vision from the retina of the eye to the brain. Disease or injury of the optic nerve can result in partial or total blindness.
UNDERSTAND
cornea is responsible for 80% of focusing power, Lens is 20%
eye accomodation
the ability of the eye to change it’s focus from distant to near objects. this process is achieved by the lens changing its place
myopia
nearsightedness
light is focused in front of retina and the eyeball is too long
hyperopia
farsightedness
light is focused behind the retina and eyeball is short
presybopia
progressively diminished ability of the eye to focus. caused by the loss of elasticity of the crystalline lens. starts around middle age 40-45
amblyopia
lazy eye- loss or lack of development of central vision in one eye that is unrelated with any health problems and not correctable with lenses.
strabismus
cross eye- condition where both eyes do not look at the same place at the same time. usually caused by poor eye muscle control or a high amount of farsightedness
blind spot
where the optic nerve leaves the eye; no visual receptors here
macular degeneration
common, painless eye condition in which the central portion of the retina deteriorates and does not function adequately
what are the eye receptors?
rods and cones
where are the visual pigment molecules located?
in their outer segments
what are the two main components of the visual pigment molecules?
opsin-protein of the retinal rods adn cones
retinal
how does visual transduction occur?
retinal absorbs one photon and changes shape. this is called isomerization. this starts an enzyme cascade
enzyme cascade
is what your brain changes what you perceive into an image
isomerization
when your retina changes shape
dark adaptation curve
rods=turtle;slow but finishes the race meaning they help you see in the dark
cones=rabbit; fast but burns out faster
-visual adaptation that occurs in the dark; during which the sensitivity to light increases
stages of dark adaptation curve
Stage 1 takes place for 3 to 4 minutes.
Then sensitivity levels off for 7 to 10 minutes - the rod-cone break.
Stage 2 shows increased sensitivity for another 20 to 30 minutes.
During this time the cones and rods are regenerating. Opsin and retinal are recombining
what happens in dark adaptation?
rods and cones are regenerating[this means the opsin and retinal are recombining
Purkinje Shift
name for enhanced sensitivity to short wavelengths (blue and greens) during dark adaptation when the shift from cone to rod vision occurs
convergence in retina
Rods and cones send signals to the bipolar cells then the ganglion cells and then out the retina through the optic nerve.
UNDERSTAND
rods an cones converge to bipolar cells and then into ganglion cells and then to the optic nerve
what is lateral inhibition in the retina?
light shown in a receptor leads to rapid rate of firing
-think of inhibitory synpases
What is the mechanism behind Hermann Grid?
your eye is trying to see something that is not there (inhibitory)
-inhibitory receptors in the white areas
what is the mechanism behind Mach Bands?
another optical illusion
-more in the light areas and less in the dark areas (inhibition)
how does simultaneous contrast work?
the change in perception of color that occurs when a colored field is surrounded by a differently colored background
what is the explanation for white’s illusion?
an area’s appearance is affected by where we perceive it belongs
