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49 Cards in this Set

  • Front
  • Back
wavelength and colors of visible radiation

visible light
visible light: 380-750 nm

gamma rays
x-rays
UV light
VISIBLE LIGHT
infared
radio wave
Wave photon duality
light travel in wave-like fashion with single packets of energy called photons
visible spectrum
ROY G BV
r: 730nm
o: 680nm
y: 630nm
g: 550nm
B: 480nm
v: 380nm
color of an object
depends on which wavelength is reflected back to the retina (not absorbed by the object)
white and black
white: all wavelengths reflected by object

black: all wavelengths absorbed by object
Light Refraction
light will bend when it passes from one medium to another
Convex Lens
thicker at center, tapered at edge

causes light to bend so that ir comes together at a focal point
Real image
image of a focal point of convex lens

inverted and reversed
Cornea
constant (unchanging) refraction
Lens
can change refraction and focal length
ciliary muscles change convexity of the lens
far point of vision
distance beyond which lens will not change its shape (20 feet)
emmetropic eye
normal healthy eye
acccomodation of lens
lens shape becomes more convex

light rays bend more sharply

shorter focal length for the closer object (ciliary muscles for lens)
near point of vision
shortest distance for focusing (maximum convexity of lens) about 8-10 inches, gets worse with age
presbyopia
poor close vision in elderly

inelasticity of lens
accomodation of pupils
constriction of pupils
better focus
less divergent rays
(constrictor muscle of iris)
convergence of the eyes
eyes rotate medially to keep image on center of the retina
(medial rectus muscles of the eyeballs)
myopia
nearsighted

distant objects are blurred, close objects are focused in from of the retina
(rather than directly on it)
eyeball too long, lens too strong
concave lens can correct light before eye
hyperopia
"farsightedness"
close objects are blurred
close objects are focused beyond the retina (rather than directly on it)

eyeball too short, poor refraction of lens
convex lens can correct light before eye
astigmatism
blurry images at all distances
unequal curves on lens and or cornea
creating discontinuous image on the retina
pigmented base of retina
outer segment (pigmented disc)
connecting stalk
inner segment (mitochondria)
outer fiber
cell body (nucleus)
inner fiber
synaptic ending
"neural layer"
bipolar cell
ganglion cell (axons carried to brain by optic nerve)
outer segment
contain membrane bound discs with pigments that absord and react to light
rods
pigment discs stacked like pennies all the way to the base, membranes are distint crom the plasma membrane

sensitive to dim light
respond to all wavelengths of color
only grey information to the brain
100 rods per ganglion cell to brain
widely spread throughout retina
not good for visual acuity
cones
pigment discs taper off toward the base, membranes are continuous with the plasma membrane
require bright light for stimulation
different cones have different pigments specific for certain wavelengths (colors)
can convey color information to brain
1-3 cones per ganglion cell to brain
primarily concentrated in fovea (center)
essential for visual acuity
opsin
transmembrane protein in the membrane of pigmented discs of rods and cones
retinal
light absorbing molecule that changes shape when struck by a photon of light
vitamin A
precursor of retinal
11-cis isomer of retinal
non-activated form of retinal, prior to absorption of photon energy, has a "kinked" double bond
all trans isomer of retinal
activated form of retinal, after struck by photon of light, double bond straightens out
all trans isomer of retinal
activated form of retinal, after struckt by photon of light, double bond straightens out
rhodopsin
visual pigment in rods
in membrance of pigmented discs of outer segments
bleaching of pigment
breakdown of rhodopsin after the absorption of light

11 cis retinals (+ scotopsin)-> rhodopsin -> all trans retinal (light + scotopsin)
all trans retinal
causes hyperpolarization of rod

Na+ channels open in dark are closed
rod is hyperpolarized (increase negativity)
Ca2+ channels in synapse close
less neurotransmitter released by the rod
photopsins
3 distint pigment in cones are sensitive to 3 different parts of the visible spectrum
blue cones
maximum sensitivity at 455 nm
green cones
maximus sensititvity at 530nm
red cones
maximum sensitivity at 625 fm
different colors
differential activation of each of the three different cones
color blindness
inherit gene for one of the photopsin proteins that is deficient (mainly male), most common are red and green mutations
Light Adaptation
very dark -> very light
rhodopsin in rods is quickly bleached out
sensitivity to shallow light disappears
rods inhibited by other retinal cells
cones are activated to take over (5 mins)
consensual pupil reflex - constriction
Dark Adaptation
very bright -> very dark
cones are gradually cease to be stimulated
bleached out rods can produce rhodopsin
rods eventually take over in the dim light
pupillary dilation pupils increase size
nyctalopia
defiency in function of rods during dim-light situations

vitamin A deficiency
visual pathway - photoreceptor to occipital cortex
retina - photoreceptors (rods and cones), bipolar cells, ganglion cells (axon = optic nerve)
axon path - optic nerve (from each eye retina), optic chiasma (medical fibers cross over), optic tracts (opposite visual fields)
thalamus - lateral geniculate body of thalamus
axon path - optic radiation (fibers to cortex)
cerebral cortex - occipital lobe, primary visual cortex
Most IMPORTANT
THALAMUS-LATERAL GENICULATE BODY OF THALAMUS
superior colliculi
control of extrinsic eye muscles
pretectal nucleus
mediate pupillary light reflexes
suprachiasmatic nucles of hypothalamus
circadian rhythm
binocular vision
two eyes have overlapping regions of the visual field, so that the same point is from slightly different angles
depth perception
a result of binocular vision in which a person can perceive relative distances based on information gathered in both eyes