40 Vision Flashcards

1
Q

Incoming light is focused on:

A

fovea

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2
Q

As an image enters the eye, it is:

A
  1. refracted by the cornea
  2. inverted through the pupil
  3. refracted by the lens
  4. projected onto fovea
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3
Q

The lens refraction abilities are controlled by:

A

ciliary muscles (under SNS and PNS control)

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4
Q

Function of sclera?

A

protective layer for the retina and the choroid


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5
Q

Function of choroid?

A

vasc bed which provides blood flow and nutrients to the photoreceptors and RPE cells

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6
Q

The retinal blood flow is supplied by:

A
  1. central retinal artery (enters through optic nerves)

2. choroid

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7
Q

The cell bodies of the photoreceptors are located in:

And project to:

A

outer nuclear layer

outer plexiform layer

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8
Q

The photoreceptors signal through:

to:

A

through the outer plexiform layer to the bipolar cells

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9
Q

Cell bodies of bipolar cells are located:

A

in the inner nuclear layer

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10
Q

The final layer of neurons in the retina are:

A

retinal ganglion cells (located in the ganglion cell layer)

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11
Q

Function of retinal pigmented epithelial cells?

A

support the photoreceptors and provide nutrients

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12
Q

Line outermost surface of retina?

A

photoreceptors

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13
Q

Function of interneurons?

A

help in convergence of the image from the millions of photoreceptors to hundreds of bipolar cells to tens of ganglion cells

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14
Q

Types of interneurons?

A

horizontal cells and amacrine cells

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15
Q

Coalesce to form optic nerve head?

A

ganglion cell axons

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16
Q

Blind spot =

A

optic nerve head

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17
Q

Structure of fovea?

A

radially displaced retinal layers

allows for minimal distortion of the image

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18
Q

Main functions of retinal pigmented epithelial cells?

A
  1. separate the vascular choroid from the neural retina
  2. phagocytose rod outer segments every 10 days
  3. absorb some of the light that comes to the photoreceptors
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19
Q

Macular degeneration results when:

A

blood vessels damage the RPE + break through their barrier –> grow into macular region of the eye

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20
Q

Light detection/transduction occurs in:

A

outer segment of rods

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21
Q

What are spherules?

A

synaptic vesicles in rods

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22
Q

Cones are (shorter/longer) and (bigger/smaller) than rods.

A

shorter, smaller

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23
Q

How is color “seen”?

A

recognized by a unique combo of L-, M- and S-cones

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24
Q

Blue cones?

A

S

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25
Q

Green cones?

A

M

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26
Q

Red cones?

A

L

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27
Q

Carried on the X-chromosome?

A

M-cone and L-cones

28
Q

Function of photoreceptors?

A

absorb quanta of light and convert to elec signal

29
Q

Occurs in rods/cones in response to light?

A

hyperpolarization

30
Q

Reaction caused by light entering?

A

converts 11-cis-retinal to all-trans retinal

31
Q

Activates rhodopsin?

Then what happens?

A

all-trans retinal

  1. Active rhodopsin can activate GTP
  2. activates cGMP PDE by removing inh subunit
  3. 

Active PDE decr cGMP levels enough to hyperpolarize mem = close Na and Ca channels
32
Q

What repolarizes the membrane?

A
  1. calcium pumped out through the Na/Ca exchanger
  2. Ca reduced in the membrane –> cGMP levels rise
    = re-polarize the membrane to pre-stimulus levels
33
Q

How do proteins return to pre-activation?

A
  1. Slowly, rhodopsin is de-P
  2. Slowly, all-trans-retinal converted back to 11-cis-retinal
  3. Rhodopsin kinase re-P rhodopsin (which is bound by arrestin)
34
Q

What removes arrestin from rhodopsin?

A

conversion of 11-cis-retinal to all-trans-retinal

35
Q

Once photoreceptors have processed the light, the signal is passed along to:

A

bipolar cells

36
Q

Detect major changes in activity levels at bipolar-ganglion cell synapse?

A

amacrine cells

37
Q

Location of cone bipolar cells?

Location of rod bipolar cells?

A

center of retina

periphery

38
Q

Help converge the signals from multiple rod photoreceptors to fewer rod bipolar cells?

A


Horizontal cells

39
Q

Alpha ganglion cells have most input from:d

A

rods

*participate little in color perception

40
Q

Structure of alpha ganglion cells?

A

extensive dendritic trees, large axons

41
Q

Alpha ganglion cells project to:

A

magnocellular layer of the lateral geniculate nucleus

42
Q

Function of alpha ganglion cells?

A

help locate the object in space


43
Q

Function of beta ganglion cells?

A

fine texture and colors

44
Q

Beta ganglion cells project to:

A

parvocellular regions in the LGN


45
Q

Structure of beta ganglion cells?

A

small receptive field

small dendritic arbors

46
Q

What does not occur in the fovea?

A

convergence

47
Q

Ratio of

cone : cone bipolar cell : ganglion cell

A

1:1:1

48
Q

Why do humans have a crisp image representation?

A

no horizontal or amacrine cell interactions in the fovea

49
Q

Why is image reverse and inverted?

A

pinpoint effect of pupil

50
Q

Decussates in optic chiasm?

A

ganglion cell axons (nasal fibers)

51
Q

How are fibers radiating to primary visual cortex organized?

A

retinotopically

52
Q

The L visual field is processed in the (R/L) visual cortex

A

R

53
Q

Which visual image does not cross?

A

temporal

54
Q

The M pathway originates from:

Projects to:

A

magnocellular ganglion cells

lateral geniculate layers 1/2 –> 4C alpha in the cortex

55
Q

What is the function of 4C alpha in the cortex?

A

space info

56
Q

The P pathway originates from:

Projects to:

A

parvocellular ganglion cells

lateral geniculate layers 3-6 –> 4C beta in the cortex

57
Q

What is the function of 4C beta in the cortex?

A

form info

58
Q

Etiology of diabetic retinopathy?

A
  1. changes in vasc (due to incr angiogenic and decr angiostatic growth factors)
  2. changes in neurons (loss of photoreceptors + ganglion cells)
59
Q

A retinal image of advanced macular degeneration shows:

A

hyperfluorescence and areas of no vascularity

60
Q

Leading cause of blindness in older people?

Leading cause of blindness in working age adults?

A

AMD

DR

61
Q

Etiology of AMD?

A

damage to choroidal vasculature breaks through the RPE cells and damages the macula

–> Central vision = lost due to damage of macula

62
Q

AMD or DR?

genetic component

A

both

63
Q

AMD or DR?

Loss of central vision

A

AMD

64
Q

AMD or DR?

loss of all vision

A

DR

65
Q

AMD or DR?

choroid NV

A

AMD

66
Q

AMD or DR?

retinal NV

A

DR

67
Q

Cause of AMD?

A

Age**
Smoking
Genetics
Changes in angiogenic/static factors