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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
Q

What is a part of the frequency spectrum of electromagnetic radiation, the same stuff that makes radio waves and gamma waves?

A

Visible light

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26
Q

Where are pigments in rods (rhodopsin) and cones (iodopsin) located?

A

Vesicular discs

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27
Q

What are vesicular discs?

A

Where pigments of rods and cones are

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28
Q

What are forms of opsin, but respond to different parts of the spectrum of visible light (about 450-700 nm)?

A

Pigments

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29
Q

How do photoreceptors respond to light?

A

By hyperpolarizing the cells and releasing less transmitter (glutamate).

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30
Q

What causes opsin to activate PDE via transducin (a G protein).

A

Light coverts 11-cis retinal (aldehyde form of vit A) to trans-retinal.

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31
Q

What is transducin?

A

A G protein

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32
Q

What effect does PDE have?

A

reduces the background levels of cGMP which closes Na+ and Ca++ channels, hyperpolarizing the cell

33
Q

What is the net effect of photoreceptors?

A

release less glutamate

34
Q

What is vision in bright light called?

A

photopic

35
Q

What is vision in dim light called?

A

Scotopic

36
Q

Do cones have high or low sensitivity and more or less pigment?

A

low; less

37
Q

Do rods have high or low sensitivity and more or less pigment?

A

high; more

38
Q

Which (rods or cones) are concentrated in the fovea?

A

cones

39
Q

Since cones are in high concentration in the fovea, do they have high or low acuity?

A

High

40
Q

Are there rods in the fovea?

A

No.

41
Q

Since there are no rods in the fovea, do they have high or low acuity?

A

Low

42
Q

What type of light is a cone sensitive to?

A

direct axial light

43
Q

What type of light is a rod sensitive to?

A

scattered light

44
Q

Which has better spatial resolution, rods or cones?

A

cones

45
Q

Which is better at detecting visual motion, rods or cones?

A

rods

46
Q

Are cones chromatic or achromatic?

A

chromatic– three types of pigmented cells responsive to different parts of the spectrum

47
Q

Are rods chromatic or achromatic?

A

achromatic– only one type of pigment (rhodopsin)

48
Q

______ are primarily in peripheral part of retina and do not code for color.

A

Rods

49
Q

______ are concentrated in fovea, but spread out thinly top provide peripheral color vision.

A

cones

50
Q

What is the center of the visual field?

A

The fovea

51
Q

SInce the fovea only has cones, what does it favor?

A

color and acuity

52
Q

How are cones exposed to more incoming light?

A

by the outward dispersal of ganglion and other integrative cells.

53
Q

What increases the acuity of vision?

A

Each cone activates a single ganglion cell

54
Q

What does Pigment turnover in photoreceptors require?

A

High levels of oxygen

55
Q

Why are photoreceptors close to the choroid blood supply?

A

They require high levels of oxygen

56
Q

How do photoreceptor inner layer cells draw nutrients?

A

from smaller retinal arteries

57
Q

Why are photoreceptors located on the outer portion of the retina?

A

Light cannot penetrate blood vessels well, photoreceptors need to be near the choroid blood supply.

58
Q

Why does light pass through ganglion and bipolar cells without distortion?

A

they have the same refractive index as the vitreous humor

59
Q

What is the cell layer deep to the photoreceptors?

A

Retinal pigment epithelium (RPE)

60
Q

What are the 5 functions of the RPE?

A

Visual acuity, antioxidant, maintain photoreceptor excitibility, nutrients, and phagocytosis

61
Q

How does RPE aid visual acuity?

A

Absorbs light passing through the retina in order to limit reflection of light back into the photoreceptors.

62
Q

How does the RPE act as an antioxidant?

A

Pigments absorb blue light, a light bandwidth that increases levels of free radicals in retinal cells.

63
Q

How does the RPE participate in the visual cycle of the retina and maintain photoreceptor excitability?

A

Trans-retinal formed by light absorption is transport from photoreceptor to RPE, reformed into 11-cis-retinal and redelivered to the photoreceptor

64
Q

How does the RPE nourish the photoreceptors?

A

Transports nutrients such as glucose and retinol to photoreceptors

65
Q

What does the RPE phagocytose?

A

Cell debris that results from light absorption.

66
Q

What is deficient uptake of membrane fragments accumulating and separating the receptors from the choroid, leading to anoxia and cell death?

A

Retinitis pigmentosa

67
Q

What is the clinical definition of a detached retina?

A

Neural retinal tears away from the pigment epithelium.

68
Q

What is the name of the condition when a blood vessel ruptures or build up of cellular wast material detaches the retina?

A

macular degeneration

69
Q

What 3 types of cells integrate information from receptor cells and activate ganglion cells?

A

Bipolar cells, horizontal, and amacrine cells

70
Q

What is the output of cells of the retina that transmit visual information to the thalamus, superior colliculus, and other brain stem areas?

A

Ganglion cells

71
Q

_____ cell axons converge at the optic disc to form the optic “nerve”

A

ganglion

72
Q

What 3 structures make up the optic nerve/tract?

A

Axons of ganglion cells, CNS glia, central artery and veins of the retina

73
Q

What is the function of the axons of ganglion cells?

A

transmit visual information to the thalamus

74
Q

What structure myelinates the axons in the optic nerve?

A

oligodendrocytes

75
Q

What structure surrounds cell bodies and dendrites and contact blood vessels?

A

Astrocytes

76
Q

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?

A

Papilledema

77
Q

Why is the optic disc considered a “blind spot”?

A

It has no receptor cells and no structures to respond to light.

78
Q

In normal, binocular vision, how is visual information within the blind spot interpolated?

A

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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