ch. 9 - eye Flashcards
(115 cards)
1
Q
wavelength
A
distance between peaks
2
Q
frequency
A
waves per second
3
Q
amplitude
A
peak minus through
4
Q
what is the visual range for humans?
A
400-700 nm
5
Q
higher frequency equals…
A
higher energy
6
Q
optics
A
the study of light rays and their interactions
7
Q
ray
A
wave of electromagnetic radiation in vacuum traveling as a straight line
8
Q
reflection
A
the bouncing of light rays off a surface; this is most of the light we see
9
Q
absorption
A
transfer of light energy to a particle or surface
10
Q
refraction
A
the bending of light rays that can occur when they travel from one transparent medium to another
11
Q
pupil
A
opening that allows light to enter the eye and reach the retina; dark because of retinal pigments
12
Q
iris
A
pigmentation provides the eye color
13
Q
muscles around iris
A
control pupil size
14
Q
cornea
A
transparent external surface that contains NO blood vessels
15
Q
sclera
A
the white of the eye, forms the tough wall of the eyeball
16
Q
extraocular muscles
A
move the eyeball in orbit (three pairs)
17
Q
conjunctiva
A
a membrane that folds back from the inside of the eyelids and attaches to the sclera
18
Q
optic nerve
A
carries axons from the retina and exits the back of the eye, passes through the orbit, and reaches the base of the brain by the pituitary gland
19
Q
optic disc
A
where the optic nerve fibers exit the retina; there are blood vessels here; form blind spot
20
Q
macula
A
the part of the retina for central vision
21
Q
fovea
A
retina is the most thin here; good reference point
22
Q
ophthalmoscope
A
a device that enables one to peer into the eye through the pupil to the retina
23
Q
ciliary muscles
A
attached to the sclera; controls shape of the lens
24
Q
aqueous humor
A
watery fluid that lies between the cornea and the lens
25
vitreous humor
lies between the lens and the retina; its pressure serves to keep the eyeball spherical
26
esotropia
cross-eyed
27
exotropia
wall-eyed
28
extraocular muscle disorders
input from one eye is suppressed
29
cataract
clouding of lens
30
glaucoma
increased intraocular pressure
31
retinitis pigmentosa
loss of peripheral and night vision
32
macular degeneration
loss of central vision
33
where is the site of most of the refractive power of the eyes?
cornea
34
what is the reactive power of the cornea?
42 diopters
35
what is the focal distance of the cornea?
2.4 cm (or 0.024m)
36
focal distance
the distance from the refractive surface to the point where parallel light rays converge
37
the tighter the curve of the cornea, the _____ the distance.
shorter
38
what does refractive power depend on?
the slowing of light at the air-cornea interface
39
accommodation
changing the shape of the lens; ciliary muscles contract, lens becomes more round, more curved
40
hyeropia
far-sightedness, convex
41
myopia
near-sightedness, concave
42
detached retina
retina pulls away from underlying wall of the eye from a blow to the head or by shrinkage of the vitreous humor
43
pupillary light reflex
produced by retina-brain stem connections
| * consensual
44
construction of pupil...
increases depth of focus
45
visual acuity
ability to distinguish between near by points
| 20/20 = 0/083 degrees
46
left visual field is imaged on what side of the retina?
RIGHT
47
right visual field is imaged on what side of the retina?
left
48
what is the most direct pathway for visual info. to exit the eye?
photoreceptors to bipolar cells to ganglion cells
49
horizontal cells
receive input from photoreceptors and project neuritis laterally to influence surrounding bipolar cells and photoreceptors
50
amacrine cells
receive input from bipolar cells and project laterally to influence surrounding ganglion cells, bipolar cells, and other amacrine cells
51
what are the ONLY light sensitive cells in the retina?
photoreceptors
52
what are the ONLY source of output from the retina?
ganglion cells
53
how is the retina organized?
in layers (laminar)
54
how does light pass?
from vitreous humor through ganglion and bipolar cells BEFORE it reaches photoreceptors
55
what is the innermost layer of the retina?
ganglion cell layer
56
what is the second layer of the retina?
inner nuclear layer: bipolar, horizontal, and amacrine cells
57
what is the third layer of the retina?
outer nuclear layer: cell bodies of photoreceptors
58
what is the last layer of the retina?
layer of photoreceptor outer segments: light sensitive elements
59
pigmented epithelium
lies below the photoreceptors, plays a critical role in the maintenance of the photoreceptors and photopigments
60
inner plexiform layer
between the ganglion cell and inner nuclear cell layers, contains the synaptic contacts between bipolar, amacrine, and ganglion cells
61
outer plexiform layer
between the outer and inner nuclear layers, where photoreceptors make synaptic contact with the bipolar and horizontal cells
62
rod photoreceptors
long, cylindrical outer segment, containing many discs
63
cone photoreceptors
shorter, tapering outer segment with fewer discs
64
night vision (scotopic)
rods bc they are 1000X more sensitive
65
dayligt (photopic)
cones
66
does the peripheral retina have more rods or cones?
RODS
67
T or F: peripheral retina has more receptors per ganglion cell
true
68
is the peripheral retina more sensitive to light?
yes, bc rods are specialized for low lights and there are more photoreceptors feeding info to each ganglion cell
69
what area is specialized for high resolution?
fovea bc there are no rods
70
is the peripheral retina good for details?
NO, it is poor for details
71
__X more rods than cones
20
72
what is the Vm of the rod outer segment?
-30 mV
73
dark current
Vm due to special Na+ channels, opened by cGMP, made by guanylate cyclase
74
in light
light reduces levels of cGMP, Na+ channels close, photoreceptor cells hyperpolarize
75
what is light absorbed by in rod outer segment?
rhodopsin
76
receptor is phototransduction
opsin
- 7 TM G-protein receptor
- retinal bound
77
retinal
a derivative of vitamin A
78
bleaching
the absorption of light causes a change in the conformation of retinal so that it activates opsin
79
what does bleaching stimulate?
the G-protein transductin, which then activates phosphodiesterase (PDE) - which breaks down cGMP
80
amplification
allows detection of single photon
81
at what wavelength do rods respond to light?
500 nm
82
what does it mean when light becomes saturated?
additional light causes no more hyperpolarization
83
at what wavelength are blue cones maximally activated?
430 nm
84
at what wavelength are green cones maximally activated?
530 nm
85
at what wavelength are red cones maximally activated?
560 nm
86
what did young show about colors?
all colors of the rainbow, including white, could be created by mixing the proper ratio of red, green, and blue light
87
young-helmholtz trichromacy theory
the brain assigns colors based on comparison of the readout of the three cone types
88
dark adaptation
getting used to the dark, takes about 20-25 mins
89
what is dark adaptation due to?
- pupil dilation
- adjustment of retinal circuitry
- making new unbleached rhodopsin
90
light adaptation
reversing the changes in the retina that were accomplished by dark adaptation, takes 5-10 mins
91
what is Ca2+ role in light adaptation?
- inhibits guanylyl cyclase
| - decreases PDE and photopigments response to light
92
who were the neuropysiologists behind retinal processing?
Hartline, Kuffler, and Barlow (1950)
93
what did they find with retinal processing?
ONLY ganglion cells fire action potentials
94
what did Dowling find in 1970s?
how retinal ganglion cells responses were affected by horizontal and bipolar cells
95
OFF-type bipolar cells
glutamate gated cation channels mediate a classical depolarizing EPSP from the influx of Na+
- "sign conserving"
- depolarize in dark
- hyperpolarize in light
96
ON-type bipolar cells
have G-protein-coupled receptors and respond to less glutamate
- "sign inverting"
- depolarize in light
- hyperpolarize in dark
97
receptive field
area of retina that when stimulated with light changes the cell's membrane potential
98
receptive field center
a circular area of retina providing direct photoreceptor input
99
receptive field surround
surrounding area of retina providing input via horizontal cells
100
1 mm on the retina is how many degrees?
3.5
101
ON response
illumination of the center causes depolarization, while illumination of the surround will causes antagonistic hyoerpolarization
102
OFF response
cell is depolarized by a spot turning from light to dark in the center, it will be hyperpolarized by the same stimulus to the surround
103
ON center ganglion cells
is depolarized and responds with a barrage of action potentials when a small spot of light is projected onto the middle of its receptive field
104
what are ganglion cells most responsive to?
differences in illumination that occur within their receptive field
105
uniform illumination
the center and surround cancel to yield some low level response
106
P ganglion cells
- 90%
- contact one to a few cone bipolar cells
- small cells
- small concentric receptive field
- sustained
- slowly adapting response
- weak response to movement
107
M ganglion cells
- 5%
- synapse with many bipolar cells
- color insensitive
- large concentric receptor field
- transient
- rapid adapting response
- responds to movement across field
108
non M - non P cells
other 5%
109
which ganglion cells are sensitive to color?
P and some nonM-nonP
110
color-opponent cells
response in center to one wavelength is canceled by other wavelength in surround
111
red-green
P cells
112
blue-yellow
nonM-nonP
113
parallel processing
- information about depth
- light and dark information
- ganglion cells have different receptive fields and response properties
114
low resolution, large field
M cells
115
small fields, fine detail
P cells
