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Ocular Physiology > Retina > Flashcards

Retina Flashcards

1
Q

Retina is red because of what compound?

A

purple rhodopsin

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2
Q

T/F: Retina grays/opacifies about 1 hr after death

A

True

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3
Q

What is the chief function of rods?

A

Detecting light and movements

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4
Q

What is the chief function of cones?

A

Color and form vision

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5
Q

Rods and cones are named based on the appearance of their what structures?

A

Outer segment

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6
Q

T/F: Retina is is thick centrally and peripherally

A

False! Retina is THIN centrally and peripherally

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7
Q

T/F: optic disc is devoid of photoreceptors

A

True. And this creates a blind spot

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8
Q

Macula lutea is yellow because of what pigment?

A

xanthophyll

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9
Q

T/F: Foveola only contains rods

A

False! Foveola contains only CONES.

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10
Q

What is the diameter of foveola

A

0.35mm

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11
Q

What are the functions of pigment epithelial cell layer?

A

Absorption of light and removal of heat
Restricts stray light; protects receptors from undesirable effects of light
Provides photoreceptors with nutrients/ O2
Reservoirs of useful substances (ex. Vit A)
Provide slow disintegration, a role in phagocytotic activity

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12
Q

Rods are shed or sloughed off when?

A

In the morning or when dark periods are over.

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13
Q

What is Nyctalopia?

A

Loss of night vision due to vitamin A deficiency.

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14
Q

T/F: Fovea does not contain any blood vessels.

A

True

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15
Q

What is the diameter of the fovea?

A

1-2 mm

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16
Q

What does the ora serrata separate?

A

Ora serrata separates the neural part of the retinal peripherally from the ciliary body.

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17
Q

How do arteries appear in fundus photograph compared to veins?

A

Arteries appear thinner and lighter compared to veins which appear wider and darker

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18
Q

What are the four subdivisions of the retina?

A
  1. Pigment Epithelial Layer
  2. Photoreceptor Layer
  3. Intermediate Cell Layer
  4. Ganglion Cell Layer
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19
Q

Do pigment epithelial cells undergo mitosis?

A

No. Pigment epithelial cells of the retina do NOT undergo mitosis

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20
Q

What happens when pigment epithelial cells are dead?

A

Cells neighbors occupy their places when they are dead.

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21
Q

Each pigment epithelial cell is in contact with how many photoreceptors?

A

Each pigment epithelium cell is in contact with an average of up to 45 photoreceptors.

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22
Q

T/F: Photoreceptors have a palisade arrangement

A

True

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23
Q

What is the rate of lamellae formation in rods and where does it take place?

A

Lamellae formed at a rate of 1-5 per hour at the bottom of the segment

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24
Q

How often can rod lamellae be completely renowned?

A

1-2 weeks

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25
Q

How long are rods? How thick?

A

Long (40-60 µm) and about 2 µm thickness

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26
Q

Where is the rhodopsin (photopigment) found in rods?

A

Found in discs and some extent plasma membrane of rod outer segment

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27
Q

T/F: Rods are very sensitive to light.

A

True

28
Q

What pigment is found in Cones?

A

Iodospin

29
Q

Why aren’t colors seen during night vision?

A

Because cones do NOT react to small amounts of light.

30
Q

When does most of cone shedding occur?

A

During end of the day (night)

31
Q

What type of light are cones most sensitive to?

A
  1. short λ/ blue
  2. medium λ/ green
  3. long λ/ red
32
Q

What kind of protein is rhodopsin? And what does it contain?

A

Rhodopsin is an intrinsic membrane protein and it contains vitamin A.

33
Q

What are the four chemical forms of Vitamin A

A
  1. Retinyl ester (storage)
  2. retinal (Visual transduction)
  3. retinoid( transport/hormonal)
  4. retnoic acid (synthesis)
34
Q

Which two proteins bind vitamin A (in the form of retnoid) while it is being transported?

A
  1. retinol binding protein (RBP) inside the cell and

2. prealbumin (PA) in the bloodstream

35
Q

What are the diatery sources of Vitamin A?

A 
β-carotene (yellow vegetables)
Retinyl esters (animal sources)
36
Q

What does excessive intake of vitamin A cause?

A

Excessive vitamin A causes increased gluconeogenesis and protein turnover

37
Q

What are the three cell types found in ganglion cell layer?

A

Magno cells (9%), parvo cells (80%), konio cells (9%)

38
Q

How many rods are there?

A

110-125 million rods

39
Q

How many cones are there?

A

6.5 million cones

40
Q

T/F: central fovea has the highest number of cones.

A

True

41
Q

What is the function of the outer limiting membrane?

A

To hold photoreceptors together

42
Q

Inner nuclear cell layer of the retina contains cell bodies of which cells?

A 
Bipolar cells
Horizontal cells
Amacrine cells
Interplexiform cells
Müeller’s connective fibers
43
Q

How deep is the ganglion cell layer at the macula? At the periphery?

A

≈10 cells deep

and about 1 cell layer peripherally

44
Q

Where is the optic disc located?

A

Located 3 mm medially to and slightly above the posterior pole

45
Q

Where is the fovea centralis located?

A

Fovea centralis is located temporal to and below the posterior pole

46
Q

What is Henle’s layer?

A

At the fovea centralis there is retinal thinning → shallow depression in the surface → nerve elements heap (pile up) to form Henle’s layer.

47
Q

T/F: only rods are found in the foveola.

A

FALSE. Only cones are found in the foveola!

48
Q

How does the avascular region of the fovea get nutrition?

A
  • Blood vessels surrounding it and

* from the choroid behind it

49
Q

Where is ora seratta?

A

*6mm infront of the equator and 8.5mm behind the limbus.

50
Q

T/F: The fovea contains blood vesssels.

A

False. There should be no blood vessels on the fovea.

51
Q

T/F: pigment epithelial cells of the retina do multiply.

A

False. There are about 5 million cells in the RPE (pigment epithelial cell layer) and they do NOT multiply.

52
Q

What kind of cells are found in the RPE (retinal pigment epithelial) layer?

A

single stratum (layer) of cells attached to the Bruch’s membrane

53
Q

The cells in the RPE are attached to what structure of the choroid?

A

Bruch’s membrane

54
Q

The photoreceptors are held together by what structure of the retina?

A

external limiting membrane

55
Q

Which cells transform light into electrical energy by chemical processes

A

Photoreceptors (cones and rods)

56
Q

T/F: In rods sensation is the same for all wavelengths of light

A

True

57
Q

Explain convergence of impulses from rods.

A

several rods connect with one bipolar cell-> convergence of signals.

58
Q

T/F: Cones are shorter than rods?

A

True

59
Q

What is the shape of cones at the fovea?

A

At the fovea, cones are more cylinderical shaped which resemble rods.

60
Q

In cones the lamellae are attached to which part of the cell?

A

To the cell membrane.

61
Q

What is Tay-Sachs?

A

*Disease is a result of hexaminodase A deficiency
(which normally breaks down gagliosides)
*this leads to an accumulation of GM2 in the retina and ganglion cells degenerate- cherry red spot
*leads to early blindness and death at 3-6yrs old

62
Q

Breakdown of hexaminodase A deficiency is a characteristic of which disease?

A

Tay-Sachs.

63
Q

Viramin A is a fat soluble vitamin. T/F?

A

True

64
Q

What does vitamin A deficency cause? Name the three diseases.

A

Nyctalopia–>Xerophthalmia–>Keratomalacia

65
Q

Retinal blood supply is mostly from which artery?

A

Central retinal artery

66
Q

T/F Capillary network is densest at the macula.

A

True

Ocular Physiology (6 decks)

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