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Organ Systems III > Vision 2 > Flashcards

Vision 2 Flashcards

1
Q

What is the nervous coat of the orbit called?

A

The retina

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2
Q

What branch of the internal carotid supplies blood to the retina?

A

Central artery of the retina

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3
Q

What is the course of the central artery of the retina?

A

Courses through optic tract and exits onto the inner surface of the retina and surrounds the macular region.

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4
Q

What is the name for the central point if the retina?

A

Fovea centralis

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5
Q

The fovea centralis only contains what?

A

Cones

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6
Q

What is the name for the yellow area around surrounding the fovea?

A

Macula lutea

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7
Q

Why is the macula lutea yellow?

A

Accumulated lutein and zeaxanthin

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8
Q

What are lutein and zeaxanthin?

A

Carotenoids derived from the diet

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9
Q

What are the 2 main functions of both lutein and zeaxanthin?

A

Reduce oxidative stress (antioxidants) and absorb excess blue and ultraviolet light

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10
Q

What is the name for the bind spot?

A

Optic disc

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11
Q

Why is the optic disc a blind spot?

A

No receptor cells

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12
Q

What does the optic disc contain?

A

Axons of ganglion cells

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13
Q

Name the retinal layers from outer to inner eye:

A

Retinal pigments epithelium, photoreceptors, neural cells, ganglion cells

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14
Q

What 2 things are the photoreceptors?

A

Rods and cones

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15
Q

What is the function of the photoreceptors?

A

Absorb visible light

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16
Q

What are rods and cones?

A

Photoreceptors

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17
Q

What are 3 types of neural cells in the retina?

A

bipolar, horizontal and amacrine cells

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18
Q

What is the function of neural cells?

A

Integrate light information

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19
Q

What is the function of the ganglion cells in the retina?

A

Project visual information to the thalamus

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20
Q

How does light reach the photoreceptors?

A

Through the other retinal layers (inverted retina)

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21
Q

What is the pigment in the outer segment of stacks of discs in rods?

A

rhodopsin

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22
Q

What is the pigment in the outer segment of stacks of discs in cones?

A

iodopsin

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23
Q

The inner segment of rods and cones (photoreceptors) contain what?

A

nucleus and synaptic terminal that release glutamate

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24
Q

The synaptic terminal of the inner segment of photoreceptors releases what?

A

glutamate

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25
What is a part of the frequency spectrum of electromagnetic radiation, the same stuff that makes radio waves and gamma waves?
Visible light
26
Where are pigments in rods (rhodopsin) and cones (iodopsin) located?
Vesicular discs
27
What are vesicular discs?
Where pigments of rods and cones are
28
What are forms of opsin, but respond to different parts of the spectrum of visible light (about 450-700 nm)?
Pigments
29
How do photoreceptors respond to light?
By hyperpolarizing the cells and releasing less transmitter (glutamate).
30
What causes opsin to activate PDE via transducin (a G protein).
Light coverts 11-cis retinal (aldehyde form of vit A) to trans-retinal.
31
What is transducin?
A G protein
32
What effect does PDE have?
reduces the background levels of cGMP which closes Na+ and Ca++ channels, hyperpolarizing the cell
33
What is the net effect of photoreceptors?
release less glutamate
34
What is vision in bright light called?
photopic
35
What is vision in dim light called?
Scotopic
36
Do cones have high or low sensitivity and more or less pigment?
low; less
37
Do rods have high or low sensitivity and more or less pigment?
high; more
38
Which (rods or cones) are concentrated in the fovea?
cones
39
Since cones are in high concentration in the fovea, do they have high or low acuity?
High
40
Are there rods in the fovea?
No.
41
Since there are no rods in the fovea, do they have high or low acuity?
Low
42
What type of light is a cone sensitive to?
direct axial light
43
What type of light is a rod sensitive to?
scattered light
44
Which has better spatial resolution, rods or cones?
cones
45
Which is better at detecting visual motion, rods or cones?
rods
46
Are cones chromatic or achromatic?
chromatic-- three types of pigmented cells responsive to different parts of the spectrum
47
Are rods chromatic or achromatic?
achromatic-- only one type of pigment (rhodopsin)
48
______ are primarily in peripheral part of retina and do not code for color.
Rods
49
______ are concentrated in fovea, but spread out thinly top provide peripheral color vision.
cones
50
What is the center of the visual field?
The fovea
51
SInce the fovea only has cones, what does it favor?
color and acuity
52
How are cones exposed to more incoming light?
by the outward dispersal of ganglion and other integrative cells.
53
What increases the acuity of vision?
Each cone activates a single ganglion cell
54
What does Pigment turnover in photoreceptors require?
High levels of oxygen
55
Why are photoreceptors close to the choroid blood supply?
They require high levels of oxygen
56
How do photoreceptor inner layer cells draw nutrients?
from smaller retinal arteries
57
Why are photoreceptors located on the outer portion of the retina?
Light cannot penetrate blood vessels well, photoreceptors need to be near the choroid blood supply.
58
Why does light pass through ganglion and bipolar cells without distortion?
they have the same refractive index as the vitreous humor
59
What is the cell layer deep to the photoreceptors?
Retinal pigment epithelium (RPE)
60
What are the 5 functions of the RPE?
Visual acuity, antioxidant, maintain photoreceptor excitibility, nutrients, and phagocytosis
61
How does RPE aid visual acuity?
Absorbs light passing through the retina in order to limit reflection of light back into the photoreceptors.
62
How does the RPE act as an antioxidant?
Pigments absorb blue light, a light bandwidth that increases levels of free radicals in retinal cells.
63
How does the RPE participate in the visual cycle of the retina and maintain photoreceptor excitability?
Trans-retinal formed by light absorption is transport from photoreceptor to RPE, reformed into 11-cis-retinal and redelivered to the photoreceptor
64
How does the RPE nourish the photoreceptors?
Transports nutrients such as glucose and retinol to photoreceptors
65
What does the RPE phagocytose?
Cell debris that results from light absorption.
66
What is deficient uptake of membrane fragments accumulating and separating the receptors from the choroid, leading to anoxia and cell death?
Retinitis pigmentosa
67
What is the clinical definition of a detached retina?
Neural retinal tears away from the pigment epithelium.
68
What is the name of the condition when a blood vessel ruptures or build up of cellular wast material detaches the retina?
macular degeneration
69
What 3 types of cells integrate information from receptor cells and activate ganglion cells?
Bipolar cells, horizontal, and amacrine cells
70
What is the output of cells of the retina that transmit visual information to the thalamus, superior colliculus, and other brain stem areas?
Ganglion cells
71
_____ cell axons converge at the optic disc to form the optic "nerve"
ganglion
72
What 3 structures make up the optic nerve/tract?
Axons of ganglion cells, CNS glia, central artery and veins of the retina
73
What is the function of the axons of ganglion cells?
transmit visual information to the thalamus
74
What structure myelinates the axons in the optic nerve?
oligodendrocytes
75
What structure surrounds cell bodies and dendrites and contact blood vessels?
Astrocytes
76
What is the name of the condition in which increased CSF pressure limits venous return from the retina, which causes edema, blurred disc margins, and tortuous veins?
Papilledema
77
Why is the optic disc considered a "blind spot"?
It has no receptor cells and no structures to respond to light.
78
In normal, binocular vision, how is visual information within the blind spot interpolated?
From adjacent areas of the retina during saccadic movements or by activity in the visual cerebral cortex.

Organ Systems III (13 decks)

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