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Neurology COPY COPY COPY COPY > Vision > Flashcards

Vision Flashcards

(72 cards)

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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
What does RPE contain? Its function
Melanin | Helps absorb some of the light that comes to the photoreceptors
26
What is drusen?
Autofluoresce that occurs from protein left in the RPE
27
What are rods names for?
Shape of the outer segment
28
Rods are responsible for?
Black and white (night) vision [scotopic]
29
Where does light transduction occur in rods?
Outer segment
30
In rods, what is the synaptic expansion called?
Spherule
31
How often do rods undergo phagocytosis? By what?
Every 10 days | RPE cell
32
What are cones named for?
Outer segment
33
What do cones process?
Color (photopic) information
34
Types of cones?
L-Cones M-Cones S-Cones
35
To what do L-Cones respond? M-Cones? S-Cones?
Long wavelengths -Red Medium wavelengths -Green Short wavelengths -Blue
36
Does each type of cone respond to a different color of light?
Yes
37
What are colors represented by?
Unique combination of L-,M-,S-cones
38
Which cones are carried on a X-chromosome?
M- and L- cones
39
What happens in color blindness?
Genetic defect causing a person to miss one type of cone
40
When does vision occur?
When rods and cones HYPERPOLARIZE to light | NOT DEPOLARIZE!!!!
41
Purpose of rods and cones?
Absorb quanta of light and convert to an electrical signal
42
What happens when light comes in?
Converts 11-cis-retinal to all-trans-retinal
43
What does all-trans-retinal activate?
Rod opsin - rhodopsin
44
Active rhodopsin activates? Which then activates?
GTP --> cGMP phosphodiesterase (PDE)
45
Active PDE in a rod does what?
Lowers cGMP lvls enough to hyperpolarize the membrane and close sodium and calcium channels
46
Closure of the sodium and calcium channels leads to?
Visual response
47
What happens when enough sodium and calcium is stuck in the membrane?
Calcium begins to be pumped out through the sodium/calcium exchanger
48
What happens to cGMP levels as calcium in the membrane is reduced?
Rise and repolarize the membrane to pre-stimulus levels --> reopening the channel
49
In rods, after the membrane is repolarized and the channels reopened what happens?
Rhodopssin is de-phosphorylated and all-trans-retinal is converted back to 11-cis-retinal
50
In rods, what happens after rhodopsin is de-phosphorylated?
rhodopsin kinase comes back to re-phosporylate rhodopsin and is bound to arrestin to render it inactive
51
Where does the signal go from the photoreceptors?
Bipolar cells
52
What modifies bipolar cells?
horizontal cells
53
Where does the signal go from bipolar cells?
Ganglion cells
54
What is located at the synapse between bipolar cells and ganglion cells? What do they do?
Amacrine cells --> detect major changes in activity levels
55
Characteristics of Alpha-Ganglion cells?
``` 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
Function of alpha-ganglion cells?
Location of object in space
57
Characteristics of Beta-Ganglion cells?
``` 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
Function of beta-ganglion cells?
Define color and texture of object
59
How do cells project out of the fovea?
radially
60
Does convergence occur in the fovea?
NO
61
Ratio of photoreceptor to ganglion cell in the fovea? What does this ratio allow?
1:1 | Crisp imaging
62
Why is the visual image reversed and inverted?
Due to pinhole effect of pupil
63
What happens in the optic chiasm to ganglion cell axons?
Partial decussation --> only nasal fibers cross
64
Where does the optic tract project to?
Lateral geniculate
65
What carries geniculate fibers to primary visual cortex in occipital lobe?
Optic radiations
66
Which cortex is the left visual field processed?
RIGHT VISUAL CORTEX
67
Describe the M pathway?
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
Descibe the P pathway?
Originates from the parvocellular ganglion cells --> projects to lateral geniculate layers 3-6 --> to layer 4C-beta in the cortex - form info
69
Causes of diabetic retinopathy?
1) Changes in vasculature - Angiogentic growth factors - Loss of angiostatic growth factors 2) Changes in neurons - Loss of photoreceptors - Loss of ganglion cells
70
Characteristics of Macular degeneration?
Choroid NV Age induced Some genetic Lose central vision
71
Characteristics of dry AMD?
Drusen Little vision loss often in 1 eye
72
Characteristics of wet AMD?
Sometimes drusen Vision Loss Progresses to both eyes

Neurology COPY COPY COPY COPY (25 decks)

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