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Block 5 Week 2 Dani > Vision 1 - von Bartheld > Flashcards

Vision 1 - von Bartheld Flashcards

1
Q

Where is the focal point of a convex lenz?

A

in front of it

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2
Q

Where is the focal point of a concave (diverging) lens?

A

behind it

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3
Q

What is known as the distance of the focal point to the lens?

A

Focal length

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4
Q

What is the basic unit of focal power?

A

diopter

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5
Q

what is the relation between diopters and focal length?

A

D= 1/f

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6
Q

How do we determine focal power?

A

Focal power = Refractive index/ Focal length

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7
Q

Glaucoma is caused by a problem with (blank)

A

Aqueous humor drainage

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8
Q

the curvature of the (blank) controls accommodation

A

lens

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9
Q

Is the accommodated lens for flat or more round?

A

more round

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10
Q

What nucleus in the brainstem is activated during accommodation?

A

Edinger-Westphal nucleus of oculomotor

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11
Q

what ganglion is activated during accomodation?

A

ciliary ganglion

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12
Q

Ciliary muscles (relax/contract) to cause the zonule fibers to relax

A

contract

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13
Q

What structure is responsible for refractive power?

A

the ANTERIOR curvature of the cornea

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14
Q

can we adjust the curvature of the cornea?

A

NO

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15
Q

can we adjust the curvature of the lens?

A

why, of course!

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16
Q

Presbyopia is the phenomenon of:

A

loss of accommodation with age

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17
Q

Myopia is more commonly known as;

A

nearsightedness

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18
Q

hyperopia is more commonly known as:

A

farsigthedness

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19
Q

myopia is a condition in which your eye is too (long/short) for your lens focal length?

A

long

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20
Q

hyperopia is a condition in which your eye is too (long/short) for your lens focal length?

A

short

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21
Q

What type of lens do you use to correct myopia?

A

concave (diverging) lens

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22
Q

what type of lens do you use to correct hyperopia?

A

convex lens

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23
Q

What is an astigmatism?

A

blurry vision due to irregular curvature of the cornea or lens–can be football shaped

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24
Q

The blind spot is the (blank), where there are no cones or rods

A

optic disc

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25
Q

What are the five cell types found in the retina?

A
  1. Cones and rods
  2. Bipolar cell
  3. Horizontal cell
  4. Amacrine cell
  5. Ganglion cell
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26
Q

the cones and rods are the (deepest/most superficial) layer (as in closest to the light?

A

deepest

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27
Q

in what layer are the horizontal cells?

A

outer plexiform layer

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28
Q

are horizontal cells pre or post synaptic between bipolar cells and cones/rods?

A

presynaptic

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29
Q

are amacrine cells pre or post synaptic between bipolar cells and ganglion cells

A

postsynaptic

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30
Q

in what layer are the amacrine cells?

A

inner plexiform layer

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31
Q

what is the general function of the amacrine and horizontal cells?

A

transmit information laterally to adjacent ganglion cells from adjacent rods/cones

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32
Q

Ganglion cells send their axons to converge at the (blank)

A

optic disc

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33
Q

Does the fovea have a high concentration of rods or cones?

A

cones

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34
Q

Where are there a large concentration of rods?

A

On the peripheral edges of globe, farthest away from the fovea

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35
Q

Does the fovea receive direct blood flow?

A

NO, it is avascular!!

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36
Q

In what range of luminance do we have the best acuity?

A

Photopic

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37
Q

At what range do we reach cone threshold for sight?

A

Mesopic zone

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38
Q

At what range do we reach the absolute threshold for vision?

A

Scotopic

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39
Q

At what range does rod saturation begin?

A

Photopic

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40
Q

Is is more debilitating to lose all of your rods or cones?

A

cones!

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41
Q

What are the three reasons that cones and rods are found closest to the pigment epithelium and not closest to the light source?

A
  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
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42
Q

What is the numerical relationship between bipolar cells and rods?

A

1 bipolar cell to 15-30 rods

43
Q

What is the numerical relationship between bipolar cells and cones?

A

1 bipolar cell to one cone

44
Q

do have rods have a higher sensitivity or acuity? what does this make them good for?

A

Sensitivity

night vision

45
Q

do have cones have a higher sensitivity or acuity? what does this make them good for?

A

acuity

high resolution vision

46
Q

Describe the membrane potential of a rod after being exposed to a flash of light?

A

They hyperpolarize and take longer to respond to the next stimulus than cones

47
Q

Describe the membrane potential of a cone after being exposed to a flash of light?

A

They hyperpolarize, and can quickly respond to another stimuli

48
Q

In the dark, a photoreceptor is (hyperpolarized/depolarized)

A

depolarized

49
Q

Shining a light on a photoreceptor leads to membrane (blank)

A

hyperpolarization

50
Q

Do photoreceptors fire AP’s?

A

No, light causes a GRADED CHANGE in membrane potential that is correlated to the INTENSITY of the light source

51
Q

Transmitter release from the synaptic terminals of the photreceptor is dependent on voltage gated (blank) ion channels

A

Calcium!

52
Q

the number of calcium channels open when the photoreceptor is in the dark is (high/low)

A

HIGH

53
Q

Na and Ca flow (in/out) from the photoreceptor when it is dark

A

IN

54
Q

K flows (in/out) from the photoreceptor when it is dark

A

OUT

55
Q

the Na/Ca channels are gated by what second messenger molecule?

A

cGMP

56
Q

Absorption of light by the photoreceptor (reduces/increases) the conc’n of cGMP

A

REDUCES, which CLOSES the channels

57
Q

What is the effect of closing the Na/Ca channels on the membrane potential?

A

HYPERpolarization

58
Q

What is the photopigment of rods?

A

Rhodopsin

59
Q

What chemical does rhodopsin contain that is the light-absorbing chromophore?

A

Retinal

60
Q

What happens to retinal when it is exposed to light?

A

11-cis-retinal to all-trans-retinal

61
Q

Activation of rhodopsin with a photon activates what protein?

A

Transducin

62
Q

Transducin activates what enzyme?

A

phosphodiesterase

63
Q

What is the purpose of the phosphodiesterase during light stimulation?

A

It breaks down cGMP, closing the Ca/Na channels

64
Q

In the retinoid recycling process, all-trans retinAL is converted to?

A

all-trans-retinOL

65
Q

What is the protein that transports trans-retinol into the pigment epithelium?

A

IRBP

66
Q

Describe the series of transformations that all-trans-retinol undergoes in the pigment epithelium?

A

trans-retinol -> trans retinyl ester -> 11 cis retinol -> 11 cis retinAL -> bound to IRBP and transported back into the rod

67
Q

Low concentrations of Ca in the (outer/inner) segment of the rod increase the activity of which two enzymes? What does this cause?

A

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
Q

Light induced closure of Ca/Na channels effects internal Ca concentration how?

A

It reduces internal calcium concentration

69
Q

Reduced internal calcium leading to decreased calcium mediated inhibtion effects photon sensitivity how?

A

Photon sensitivity is reduced

70
Q

do cones or rods adapt more quickly to the dark?

A

Cones

71
Q

Do cones or rods show a greater sensitivity in the dark?

A

Rods by about 100x

72
Q

How many pigments do cones have?

A

3

73
Q

How many pigments do rods have

A

1

74
Q

What are the three pigments in cones?

A

Short (blue), medium (green), long (red)

75
Q

color pigment genes are on what chromosome?

A

X chromosome

76
Q

Which two pigments lie adjacent to each other? What does this tell us about color blindness?

A

Red and green; it explains why red-green is the most common and more common in males

77
Q

A dichromat is someone who…

A

only has two types of cones, usually with a red-green hybrid or no green at all

78
Q

There is high sequence homology between which two cones?

A

Green and red

79
Q

Protanopia is color blindness which is missing which cone?

A

Red

80
Q

Deuteranopia is color blindness missing which cone

A

Green

81
Q

When light is shone in the receptive field of on-center ganglia, what happens?

A

They fire a burst of APs

82
Q

When a dark spot is left in the center of a receptive field, what do the off-center ganglia do?

A

They fire a burst of AP’s while the on-center ganglia are inactive

83
Q

Light in the center and the surrounding ring of of the receptive field causes on and off center ganglia to do what?

A

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
Q

Perception of light intensity is dependent on (blank and blank)

A

context and background

85
Q

The closer the light to the center of a receptive field, the more (blank) per second from the on-center ganglia

A

impulses

86
Q

the on-center ganglia that would have the highest level of spontaneous activity would lie where on a light-dark interface?

A

On the actual edge/interface between the light and dark areas

87
Q

Why is it that on-center ganglia will have higher activity if they are on a light-dark edge?

A

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
Q

What is the importance of the fact that there is increased activity from the light-dark edge?

A

the retina gives special importance ( by sheer volume of activity) to better distinguish differences in luminance

89
Q

Bipolar cells have graded potentials or action potentials?

A

graded

90
Q

Graded depolarization of bipolar cells releases (more/less) (blank) neurotransmitter

A

more glutamate!

91
Q

on-center ganglia have what types of neurotransmitter receptors?

A

AMPA
kainate
NMDA

92
Q

Off-center ganglia have (blank) class of receptors, and specifically which two?

A

ionotropic
AMPA
kainate

93
Q

On-center ganglia have a (blank) class glutamate receptor called?

A

metabotropic

mGluR6

94
Q

Glutamate does what to the potential of on-center ganglia?

A

depolarize

95
Q

Glutamate does what to the potential of the off-center ganglia?

A

hyperpolarize

96
Q

Light stimulation of the surrounding field alters horizontal cell potential how?

A

it hyperpolarizes

97
Q

Light stimulation of surround field leads to what change in horizontal cell neurotransmitter release?

A

they release LESS GABA onto the photoreceptor terminals

98
Q

What is the effect of decreased GABA on photoreceptor terminals?

A

it depolarizes the center cone terminal, offsetting the hyperpolarization from the center cone

99
Q

What layer of the retina are the cell bodies of the photoreceptors in ?

A

Outer nuclear layer

100
Q

In what layer are the connections between the horizontal cells and the photoreceptors and bipolar cells?

A

Outer plexiform layer

101
Q

What cell bodies are in the inner nuclear layer?

A

Horizontal cells
Amacrine cells
Bipolar cells

102
Q

the inner plexiform layer contains synapses between which cells?

A

Amacrine cells, bipolar cells, and ganglion cells

103
Q

Gaglion cells are in which retinal layer?

A

Ganglion cell layer, derp

Block 5 Week 2 Dani (10 decks)

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