Vision 1 - von Bartheld Flashcards
(103 cards)
1
Q
Where is the focal point of a convex lenz?
A
in front of it
2
Q
Where is the focal point of a concave (diverging) lens?
A
behind it
3
Q
What is known as the distance of the focal point to the lens?
A
Focal length
4
Q
What is the basic unit of focal power?
A
diopter
5
Q
what is the relation between diopters and focal length?
A
D= 1/f
6
Q
How do we determine focal power?
A
Focal power = Refractive index/ Focal length
7
Q
Glaucoma is caused by a problem with (blank)
A
Aqueous humor drainage
8
Q
the curvature of the (blank) controls accommodation
A
lens
9
Q
Is the accommodated lens for flat or more round?
A
more round
10
Q
What nucleus in the brainstem is activated during accommodation?
A
Edinger-Westphal nucleus of oculomotor
11
Q
what ganglion is activated during accomodation?
A
ciliary ganglion
12
Q
Ciliary muscles (relax/contract) to cause the zonule fibers to relax
A
contract
13
Q
What structure is responsible for refractive power?
A
the ANTERIOR curvature of the cornea
14
Q
can we adjust the curvature of the cornea?
A
NO
15
Q
can we adjust the curvature of the lens?
A
why, of course!
16
Q
Presbyopia is the phenomenon of:
A
loss of accommodation with age
17
Q
Myopia is more commonly known as;
A
nearsightedness
18
Q
hyperopia is more commonly known as:
A
farsigthedness
19
Q
myopia is a condition in which your eye is too (long/short) for your lens focal length?
A
long
20
Q
hyperopia is a condition in which your eye is too (long/short) for your lens focal length?
A
short
21
Q
What type of lens do you use to correct myopia?
A
concave (diverging) lens
22
Q
what type of lens do you use to correct hyperopia?
A
convex lens
23
Q
What is an astigmatism?
A
blurry vision due to irregular curvature of the cornea or lens–can be football shaped
24
Q
The blind spot is the (blank), where there are no cones or rods
A
optic disc
25
What are the five cell types found in the retina?
1. Cones and rods
2. Bipolar cell
3. Horizontal cell
4. Amacrine cell
5. Ganglion cell
26
the cones and rods are the (deepest/most superficial) layer (as in closest to the light?
deepest
27
in what layer are the horizontal cells?
outer plexiform layer
28
are horizontal cells pre or post synaptic between bipolar cells and cones/rods?
presynaptic
29
are amacrine cells pre or post synaptic between bipolar cells and ganglion cells
postsynaptic
30
in what layer are the amacrine cells?
inner plexiform layer
31
what is the general function of the amacrine and horizontal cells?
transmit information laterally to adjacent ganglion cells from adjacent rods/cones
32
Ganglion cells send their axons to converge at the (blank)
optic disc
33
Does the fovea have a high concentration of rods or cones?
cones
34
Where are there a large concentration of rods?
On the peripheral edges of globe, farthest away from the fovea
35
Does the fovea receive direct blood flow?
NO, it is avascular!!
36
In what range of luminance do we have the best acuity?
Photopic
37
At what range do we reach cone threshold for sight?
Mesopic zone
38
At what range do we reach the absolute threshold for vision?
Scotopic
39
At what range does rod saturation begin?
Photopic
40
Is is more debilitating to lose all of your rods or cones?
cones!
41
What are the three reasons that cones and rods are found closest to the pigment epithelium and not closest to the light source?
1. Photoreceptor discs must be regenerated every 12 days
2. Photopigments must be recycled continuously
3. Being deep puts them closest to the blood supply from the choroid
42
What is the numerical relationship between bipolar cells and rods?
1 bipolar cell to 15-30 rods
43
What is the numerical relationship between bipolar cells and cones?
1 bipolar cell to one cone
44
do have rods have a higher sensitivity or acuity? what does this make them good for?
Sensitivity
| night vision
45
do have cones have a higher sensitivity or acuity? what does this make them good for?
acuity
| high resolution vision
46
Describe the membrane potential of a rod after being exposed to a flash of light?
They hyperpolarize and take longer to respond to the next stimulus than cones
47
Describe the membrane potential of a cone after being exposed to a flash of light?
They hyperpolarize, and can quickly respond to another stimuli
48
In the dark, a photoreceptor is (hyperpolarized/depolarized)
depolarized
49
Shining a light on a photoreceptor leads to membrane (blank)
hyperpolarization
50
Do photoreceptors fire AP's?
No, light causes a GRADED CHANGE in membrane potential that is correlated to the INTENSITY of the light source
51
Transmitter release from the synaptic terminals of the photreceptor is dependent on voltage gated (blank) ion channels
Calcium!
52
the number of calcium channels open when the photoreceptor is in the dark is (high/low)
HIGH
53
Na and Ca flow (in/out) from the photoreceptor when it is dark
IN
54
K flows (in/out) from the photoreceptor when it is dark
OUT
55
the Na/Ca channels are gated by what second messenger molecule?
cGMP
56
Absorption of light by the photoreceptor (reduces/increases) the conc'n of cGMP
REDUCES, which CLOSES the channels
57
What is the effect of closing the Na/Ca channels on the membrane potential?
HYPERpolarization
58
What is the photopigment of rods?
Rhodopsin
59
What chemical does rhodopsin contain that is the light-absorbing chromophore?
Retinal
60
What happens to retinal when it is exposed to light?
11-cis-retinal to all-trans-retinal
61
Activation of rhodopsin with a photon activates what protein?
Transducin
62
Transducin activates what enzyme?
phosphodiesterase
63
What is the purpose of the phosphodiesterase during light stimulation?
It breaks down cGMP, closing the Ca/Na channels
64
In the retinoid recycling process, all-trans retinAL is converted to?
all-trans-retinOL
65
What is the protein that transports trans-retinol into the pigment epithelium?
IRBP
66
Describe the series of transformations that all-trans-retinol undergoes in the pigment epithelium?
trans-retinol -> trans retinyl ester -> 11 cis retinol -> 11 cis retinAL -> bound to IRBP and transported back into the rod
67
Low concentrations of Ca in the (outer/inner) segment of the rod increase the activity of which two enzymes? What does this cause?
outer
guanylate cyclase
rhodopsin kinase
increased Ca/Na channel affinity for cGMP ultimately reducing the impact of light induced reductions of cGMP levels -> leading to light adaptation
68
Light induced closure of Ca/Na channels effects internal Ca concentration how?
It reduces internal calcium concentration
69
Reduced internal calcium leading to decreased calcium mediated inhibtion effects photon sensitivity how?
Photon sensitivity is reduced
70
do cones or rods adapt more quickly to the dark?
Cones
71
Do cones or rods show a greater sensitivity in the dark?
Rods by about 100x
72
How many pigments do cones have?
3
73
How many pigments do rods have
1
74
What are the three pigments in cones?
Short (blue), medium (green), long (red)
75
color pigment genes are on what chromosome?
X chromosome
76
Which two pigments lie adjacent to each other? What does this tell us about color blindness?
Red and green; it explains why red-green is the most common and more common in males
77
A dichromat is someone who...
only has two types of cones, usually with a red-green hybrid or no green at all
78
There is high sequence homology between which two cones?
Green and red
79
Protanopia is color blindness which is missing which cone?
Red
80
Deuteranopia is color blindness missing which cone
Green
81
When light is shone in the receptive field of on-center ganglia, what happens?
They fire a burst of APs
82
When a dark spot is left in the center of a receptive field, what do the off-center ganglia do?
They fire a burst of AP's while the on-center ganglia are inactive
83
Light in the center and the surrounding ring of of the receptive field causes on and off center ganglia to do what?
Both on and off center fire several AP's, but not as many as just the on-centers during a center-only light stimulation
84
Perception of light intensity is dependent on (blank and blank)
context and background
85
The closer the light to the center of a receptive field, the more (blank) per second from the on-center ganglia
impulses
86
the on-center ganglia that would have the highest level of spontaneous activity would lie where on a light-dark interface?
On the actual edge/interface between the light and dark areas
87
Why is it that on-center ganglia will have higher activity if they are on a light-dark edge?
On-center ganglia have a higher rate of action when light is confined to their center field rather than a uniform distribution of light across the visual field
88
What is the importance of the fact that there is increased activity from the light-dark edge?
the retina gives special importance ( by sheer volume of activity) to better distinguish differences in luminance
89
Bipolar cells have graded potentials or action potentials?
graded
90
Graded depolarization of bipolar cells releases (more/less) (blank) neurotransmitter
more glutamate!
91
on-center ganglia have what types of neurotransmitter receptors?
AMPA
kainate
NMDA
92
Off-center ganglia have (blank) class of receptors, and specifically which two?
ionotropic
AMPA
kainate
93
On-center ganglia have a (blank) class glutamate receptor called?
metabotropic
| mGluR6
94
Glutamate does what to the potential of on-center ganglia?
depolarize
95
Glutamate does what to the potential of the off-center ganglia?
hyperpolarize
96
Light stimulation of the surrounding field alters horizontal cell potential how?
it hyperpolarizes
97
Light stimulation of surround field leads to what change in horizontal cell neurotransmitter release?
they release LESS GABA onto the photoreceptor terminals
98
What is the effect of decreased GABA on photoreceptor terminals?
it depolarizes the center cone terminal, offsetting the hyperpolarization from the center cone
99
What layer of the retina are the cell bodies of the photoreceptors in ?
Outer nuclear layer
100
In what layer are the connections between the horizontal cells and the photoreceptors and bipolar cells?
Outer plexiform layer
101
What cell bodies are in the inner nuclear layer?
Horizontal cells
Amacrine cells
Bipolar cells
102
the inner plexiform layer contains synapses between which cells?
Amacrine cells, bipolar cells, and ganglion cells
103
Gaglion cells are in which retinal layer?
Ganglion cell layer, derp
