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Neurology > Vision > Flashcards

Vision Flashcards

1
Q

How much of the brain mass is devoted to visual processing?

A

Half

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2
Q

The occipital cortex is used for?

A

Perception of objects in space

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3
Q

Where are visual memories stored?

A

Parietal and temporal lobe

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4
Q

Visual reflexes are provided by what?

A

Brain Stem and Spinal Cord

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5
Q

Where do parts of the visual system that provide information requiring for setting the circadian rhythms, general metabolic rate, mood, etc. occur?

A

Pineal gland & diencephalon

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6
Q

Questions on visual memory help test?

A

Cognitive status

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7
Q

Pupil dilation can help test?

A

Sympathetic nerve function

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8
Q

What allows for fine focusing of incoming light?

A

Fovea

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9
Q

As light enters the eye what refracts it? Inverts it? Then variably refracted by?

A

Cornea
Pupil
Lens

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10
Q

What is the lens under the control of?

A

Suspensory ligaments

Ciliary muscles

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11
Q

What is the fovea the center of?

A

Macula

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12
Q

What is the sclera?

A

Protective layer for the retina and the choroid

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13
Q

What is the choroid?

A

Vascular bed of the outer retina

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14
Q

To what does the choroid provide blood flow and nutrients to?

A

Photoreceptors and RPE cells

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15
Q

What provides retinal blood flow?

A

Central retinal artery

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16
Q

Where does the central retinal artery enter?

A

Through the optic nerves

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17
Q

How much blood does the central retinal artery provide?

A

20%

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18
Q

Are there blood vessels in the fovea?

A

Nope

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19
Q

What helps maintain the visual axis of the fovea?

A

Extraocular muscles

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20
Q

Function of the retinal pigmented epithelial cells (RPE)?

A

Provide a barrier to the retina from the choroid

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21
Q

What is the retinal pathway?

A

Photoreceptors to bipolars to ganglion cells

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22
Q

Where do ganglion cell axons coalesce? What happens there?

A

Form optic nerve head

Blind spot

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23
Q

Types of interneurons?

A 
Horizontal cells (outer plexiform)
Amacrines (inner plexiform)
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24
Q

Other functions of the RPE?

A

Phagocytosis of rod outer segments
Retinal nutrition
Protection of photoreceptors from light damage

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25
Q

What does RPE contain? Its function

A

Melanin

Helps absorb some of the light that comes to the photoreceptors

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26
Q

What is drusen?

A

Autofluoresce that occurs from protein left in the RPE

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27
Q

What are rods names for?

A

Shape of the outer segment

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28
Q

Rods are responsible for?

A

Black and white (night) vision [scotopic]

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29
Q

Where does light transduction occur in rods?

A

Outer segment

30
Q

In rods, what is the synaptic expansion called?

A

Spherule

31
Q

How often do rods undergo phagocytosis? By what?

A

Every 10 days

RPE cell

32
Q

What are cones named for?

A

Outer segment

33
Q

What do cones process?

A

Color (photopic) information

34
Q

Types of cones?

A

L-Cones
M-Cones
S-Cones

35
Q

To what do L-Cones respond? M-Cones? S-Cones?

A

Long wavelengths -Red
Medium wavelengths -Green
Short wavelengths -Blue

36
Q

Does each type of cone respond to a different color of light?

A

Yes

37
Q

What are colors represented by?

A

Unique combination of L-,M-,S-cones

38
Q

Which cones are carried on a X-chromosome?

A

M- and L- cones

39
Q

What happens in color blindness?

A

Genetic defect causing a person to miss one type of cone

40
Q

When does vision occur?

A

When rods and cones HYPERPOLARIZE to light

NOT DEPOLARIZE!!!!

41
Q

Purpose of rods and cones?

A

Absorb quanta of light and convert to an electrical signal

42
Q

What happens when light comes in?

A

Converts 11-cis-retinal to all-trans-retinal

43
Q

What does all-trans-retinal activate?

A

Rod opsin - rhodopsin

44
Q

Active rhodopsin activates? Which then activates?

A

GTP –> cGMP phosphodiesterase (PDE)

45
Q

Active PDE in a rod does what?

A

Lowers cGMP lvls enough to hyperpolarize the membrane and close sodium and calcium channels

46
Q

Closure of the sodium and calcium channels leads to?

A

Visual response

47
Q

What happens when enough sodium and calcium is stuck in the membrane?

A

Calcium begins to be pumped out through the sodium/calcium exchanger

48
Q

What happens to cGMP levels as calcium in the membrane is reduced?

A

Rise and repolarize the membrane to pre-stimulus levels –> reopening the channel

49
Q

In rods, after the membrane is repolarized and the channels reopened what happens?

A

Rhodopssin is de-phosphorylated and all-trans-retinal is converted back to 11-cis-retinal

50
Q

In rods, what happens after rhodopsin is de-phosphorylated?

A

rhodopsin kinase comes back to re-phosporylate rhodopsin and is bound to arrestin to render it inactive

51
Q

Where does the signal go from the photoreceptors?

A

Bipolar cells

52
Q

What modifies bipolar cells?

A

horizontal cells

53
Q

Where does the signal go from bipolar cells?

A

Ganglion cells

54
Q

What is located at the synapse between bipolar cells and ganglion cells? What do they do?

A

Amacrine cells –> detect major changes in activity levels

55
Q

Characteristics of Alpha-Ganglion cells?

A 
Predominate in the peripheral retina
Most input from rods
Extensive dendritic tree
Large axons
Participate little in color perception
Project to Magnocellular layer of lateral geniculate nucleus
56
Q

Function of alpha-ganglion cells?

A

Location of object in space

57
Q

Characteristics of Beta-Ganglion cells?

A 
Primarily in central retina
Most inputs from cones
small receptive fields
Small dendritic arbors
responsive to color stimuli
project to parvocellular region in lateral geniculate nucleus
58
Q

Function of beta-ganglion cells?

A

Define color and texture of object

59
Q

How do cells project out of the fovea?

A

radially

60
Q

Does convergence occur in the fovea?

A

NO

61
Q

Ratio of photoreceptor to ganglion cell in the fovea? What does this ratio allow?

A

1:1

Crisp imaging

62
Q

Why is the visual image reversed and inverted?

A

Due to pinhole effect of pupil

63
Q

What happens in the optic chiasm to ganglion cell axons?

A

Partial decussation –> only nasal fibers cross

64
Q

Where does the optic tract project to?

A

Lateral geniculate

65
Q

What carries geniculate fibers to primary visual cortex in occipital lobe?

A

Optic radiations

66
Q

Which cortex is the left visual field processed?

A

RIGHT VISUAL CORTEX

67
Q

Describe the M pathway?

A

Originates from the magnocellular (alpha) ganglion cells –> projects to lateral geniculate layers 1 and 2 –> to layer 4C-alpha in the cortex - space info

68
Q

Descibe the P pathway?

A

Originates from the parvocellular ganglion cells –> projects to lateral geniculate layers 3-6 –> to layer 4C-beta in the cortex - form info

69
Q

Causes of diabetic retinopathy?

A

1) Changes in vasculature
- Angiogentic growth factors
- Loss of angiostatic growth factors
2) Changes in neurons
- Loss of photoreceptors
- Loss of ganglion cells

70
Q

Characteristics of Macular degeneration?

A

Choroid NV
Age induced
Some genetic
Lose central vision

71
Q

Characteristics of dry AMD?

A

Drusen
Little vision loss
often in 1 eye

72
Q

Characteristics of wet AMD?

A

Sometimes drusen
Vision Loss
Progresses to both eyes

Neurology (25 decks)

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