eye Flashcards
pupil
opening that allows light to enter the eye and reach the retina
why is the pupil dark
there is light absorbing pigment in the retina
iris
gives eye its color. contains two muscles. one that makes pupil smaller when it contracts and the other which makes it larger
cornea
glassy transparent external surface of eye that is continuous with sclera
sclera
white of the eye which forms the tough wall of the eyeball
eyes orbit
bony socket in skull where eyeball sits
extraocular muscles
move eyeball in orbit. inserted into sclera. they are not visible because they lie behind the conjunctiva
conjunctiva
membrane that folds back from the inside of the eyelids and attaches to the sclera
optic nerve
carries axons from retina, passes through orbit and reaches the base of the brain near the pituitary gland
device that enables one to peer into the eye through the pupil to the retina
ophthalmoscope
optic disk
pale circular region where retinal vessels originate. also where optic nerve fibers exist from the retina
sensation of light cannot occur here because there are no photoreceptors
why can’t the sensation of light occur at the optic disc, why are we not aware of holes in our vision
no photoreceptors here. sansation cant exist where blood vessels are because it would cast shadows on the retina
we cant see holes in out vision because our brain fills in blind spot
macula
latin word for “spot” its in the middle of each retina for central vision.
dark colored region with yellow hue. no blood vessels here
fova
dark spot 2 mm in diameter
latin word for “pit” the retina is thinner in the fova than elsewhere
since it marks center of retina, its a convenient anatomical reference point
part of retina that lies closer to nose than fova is referred to as…
nasal
part of retina that lies near temple is called..
superior…the part below is inferior
retina
contains photoreceptors specialized to convert light energy into neural activity
detects differences in light
actually part of brain
lateral geniculate nucleus (lgn)
first synaptic relay in the pathway that serves visual perception
group of cells of the dorsal thalamus
sends visual information to cerebral cortex where it is interpreted and remembered
wavelengths
distance between successive peaks or troughs
frequency
number of waves per second
amplitude
difference between wave trough and peak
what colors consist of light with longer wavelength and has less energy
warm colors like red and orange
reflection
light bouncing off a surface
absorbtion
transfer of light energy to a particle or surface
you can feel this when sun warms you up
refraction
the bending of light rays that can occur when they travel from one transparent medium to another
ex-why legs look weird in pool is a result of refraction
light passes through are _____ than water
more rapidly
since the cornea lacks blood vessels, what nourishes it?
aqueous humor
lens
its transparent and changes shape enables eyes to adjust to different differences
zonule fibers
ligaments that suspend the lens. attached to the ciliary muscle
ciliary muscle
forms ring inside eye
vitreous humor
lies between the lens and the retina. serves to keep the eyeball spherical
the lens divides the interior of the eye into two compartments containing slightly different fluids, what are they?
aqueous humor-watery fluid that lies between cornea and the lens
vitreous humor-lies between the lens and the retina, it keeps the eyeball spherical
vitreous humor
fluid between the lens and retina. it keeps the eyeball spherical
why is cornea rather than lens most refractive area of the eye
light reaches eye through air and cornea is mostly made of water
why do we see star as point of light instead of big splotches
since its a great distance, the light hits our eye virtually parallel
because eye uses refraction to focus all the stars light reaching the cornea into small point on the retina
focal distance
distance from refractive surface to the point where parallel light rays converge
light that enters the eye perpendicular to the corneal surface passes..
straight to the retina
light rays that strike the curved surface of the retina
bent so they converge on back of retina
focal distance depends on..
curvature of the cornea-the tighter the curve, the shorter the focal distance
diopeter
unit that shows reciprocal of the focal distance
macular degeneration
lose central vision
retinitis pigmentosa
degeneration of photoreceptors
cataract
clouding of lens
why is refraction of the cornea important
focuses light on the retina at the back of the eye
difference between predator and prey location of eyes
predators have eyes in front of face while prey have them more toward side so they can see further behind
nearsighted
myopia-concave lenses
when eyeball is too long, parallel rays will converge before the retina
farsighted
hyperopia-corrected with convex glass
od
right
os
left
-
nearsighted
+
farsighted
20/40
when second number is bigger, you are nearsighted
40/20
when first number is bigger, you are farsighted
where do rods and cones send information
ganglion cells
rods and cones have proteins that do what
change shape
laminar organization
cells are organized into layers
what happens when light bends rod proteins
it sets off g protein coupled receptor (metabotropic)
charged with atp
what happens when light hits rod
it depolarizes
vision during the day depends on cones because rods are?????
saturated/hyperpolarized??
why did color evolve
so we can see if fruit is ripe
astigmatism
when eyes have irregularities such as curvature and refraction in the horizontal and vertical planes is different
corrected with an artificial lens that is curved more along one axis than others
presbyopia
when lens is unable to change shape to focus
pupillary light reflex
when pupils shrink when you turn light on
involves connections between retina and neurons in brain stem which control muscles that constrict pupils
increases depth of focus
consensual
shining a light in one eye and both contract. if this doesnt happen its a sign of a brain stem disorder
visual feild
the points where you can no longer see out of perephial vision
upper field of vision is located on ___ of retina while lower is located ___
upper-bottom
bottom-up
visual acuity
ability of eye to distinguish two points near each other
depends on spacing of photoreceptors in retina and precision of eyes refraction
visual angle
distance across retina can be described in terms of degrees
most direct pathway for visual information to exit the eye
photoreceptors
bipolar cells
ganglion cells
photoreceptors
respond to light and influence membrane potential of bipolar cells connected to them
ganglion cells
fire action potentials in response to light and impulses travel down axon nerve to rest of brain
horizontal cells
receive input from photoreceptors
amacrine cells
receive input from bipolar cells
only light sensitive cells in retina
rods and cones (with exception with some ganglion cells)
only source of output cells from retina
ganglion cells
only retinal neurons that fire action potentials
ganglion cells
Why is our vision blurry underwater
Refractive power depends on the slowing of light at the air-cornea interface. If we replace air with a medium that passes light at about the same speed as the internal structure of the eye, the refractive power of the cornea would be eliminated
How does lens accommodate to focus on distant point
Ciliary muscles relax, stretching the zondle fibers and flattening the lens
How does lens accommodate to focus on neat objects
Since near objects require greater refraction provided with a more spherical lens, it is achieved by contracting the ciliary muscles so there is less tension in the zondle fibers
Where are most of cones located?
In fova
Not many cones in retinal periphery
Where are rods located
In periphery retina. There are no rods in central fova
Where do we have most spatial sensitivity
Central retina
how many photopigments/cones do we have
3
what kinds of cones do we have
L (warm)
M (mid green/warmish)
S (cool)
fovia take up___% of processing in occipital lobe
50% even if though it takes up 10% of visual field
retinotopy
map of retina
tonotopy
mapping of sounds/frequencies
ganglion cells are looking for…
specific stimulus in right place. theyre all different. certain circles surrounded by light/dark
what gives us the ability to detect lines?
what the pattern of LGN cells are activated
cells in v1 detect..
dots colors edges lines orientation
face recognitions is in..
in v1
