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Ocular Block 7 > Retina Histology > Flashcards

Retina Histology Flashcards

1
Q

Light must pass through what before it can be converted

A

All the layers of the retina

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2
Q

Light must pass through all the layers of the retina to reach the 1st order neuron where it is converted into a neural signal by phototransduction. The neural signal is modified by 2nd and 3rd order neurons and sent to the brain

A

Yes

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3
Q

What is the function of the retina

A

Light energy is transformed into a neural signal

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4
Q

What are the first 3 cells of the visual pathway held in the retina

A

1st photoreceptors
2nd bipolar
3rd ganglion

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5
Q

What are the 10 layers of the retina

A 
RPE
PRL
ELM
ONL
OPL
INL
IPL
RGCL
RNFL
ILM
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6
Q

What is the role of photoreceptors

A

Absorb light photons and convert them to signal by phototransduction

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7
Q

What are the 2 types of photoreceptors

A

Rods and cones

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8
Q

What is the photopigment of the rods

A

Rhodopsin

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9
Q

Where is the peak absorption of rhodopsin

A

500nm (blue-green

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10
Q

What is rhodopsin composed of

A

Opsin and 11-cis-retinal

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11
Q

When is the rod outer segment shed

A

Early in the morning

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12
Q

What happens to the shed outer segments of photoreceptors

A

The discs are engulfed and either
A. Become phagosomes in RPE
B. Broken down by lysis
C. Remain as lipofuscin or a Drusen

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13
Q

How long does it take to turnover the entire rod outer segment

A

2 weeks

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14
Q

What is Retinitis pigmentosa

What causes it?

A

Progressive degeneration of rod photoreceptors

100 mutations in the rhodopsin gene

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15
Q

How does retinitis pigmentosa progress

A

In mid-peripheral retina and progresses towards the central and peripheral retina leaving only a small island of cones in the macula

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16
Q

What is the chief complaint of retinitis pigmentosa

A

Difficulty with night vision (especially when driving)

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17
Q

The vision loss that occurs with RP is best described as

A

Tunnel vision

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18
Q

What is the arrangement of microbtubules in the cilium of rods

A

9+0

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19
Q

What is the function of the connecting cilum

A

Bridge between the out and inner segment of rods

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20
Q

What are the 2 regions of the rod inner segment

A

Ellipsoid

Myoid

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21
Q

Describe the ellipsoid region of rod inner segment

A

Closer to outer segment and has MITOCHONDRIA

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22
Q

Describe the myoid region of the rod inner segment

A

Closer to the cell body

Contains rER, ribosomes, Golgi

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23
Q

What is the rod outer fiber

A

Extends from the inner segment to the cell body

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24
Q

What is the inner fiber of the rod

A

Axon the rod

Has microtubules and extends from the cell body to the spherule

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25
Q

What is the rod spherule

A

Synaptic terminal of rod

Contains mitochondria, vesicles, microtubules

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26
Q

What is the triad of the rod spherule

A

Process from the horizontal cells and dendrites from rod bipolar cells invaginate

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27
Q

How many triads does a rod spherule have

A

1

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28
Q

How many rods are there

A

92-120 million

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29
Q

When are rods active

A

In dim conditions

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30
Q

Where does the rod density peak at

A

18 degrees from the center of the fovea

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31
Q

Where are there NO cones

A

In the fovea

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32
Q

What makes up the discs in the cone

What affect does this have

A

Invagination of the plasma membrane

The discs are in contact with extracellular environment

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33
Q

What are the 3 opsins of the cones

A

S(blue) 488 nm
M(green) 531 nm
L(red) 588 nm

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34
Q

What is dichromacy

A

When one of the 3 cone photopigments is absent and color is reduced to 2 dimension

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35
Q

What are th categories of dichromate

A

Protanope
Deuteranope
Tritanope

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36
Q

Protanopes lack

A

L cones

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37
Q

Deuteranopes lack

A

M cones

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38
Q

Tritanopes lack

A

S cone

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39
Q

Protanopes have a ______ problem discriminating ______

A

Severe

Red-greens

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40
Q

Deuteranopes have a ____ discriminating ______

A

Mild

Red-green

41
Q

Tritanopes have a hard time discriminating

A

Blue green

Yellow-pink

42
Q

What is the function of the connecting cilum in cones

A

Connect the outer and inner segment of the cones

43
Q

How does the inner segment of the cone differ from the rods

A

Ellipsoid region is much broader and contains greater number of mitochondria

44
Q

How does the outer fiber of the cone differ from the rods

A

Very short and sometimes absent

45
Q

Describe the cone cell body

A

Monolayer
In outermost layer of ONL
Occupy all rows in ONL
Larger than in rods

46
Q

What is the function of the inner fiber in cones

A

Axon
Has microtubules
Extends from cell body to pedicle in OPL

47
Q

Cone fibers that are oriented obliquely in the fovea are called this

A

Henle fibers

OPL in the fovea is known as Henle’s fiber layer

48
Q

What is the equivalent of the cone pedicle in rods

A

Spherule

49
Q

What is the pedicle of the cones

A

Synaptic terminal

Has mitochondria, synaptic vesicles, microtubules

50
Q

What forms the triad in cone pedicle

A

Invaginating midget cone bipolar cells

51
Q

Each pedicle has how many ribbons and triads

A

30 ribbons

30 triads

52
Q

What neurotransmitter is released from cones

A

Glutamate

53
Q

How many cones are there

A

5-6 million

54
Q

Where are 10% of the cones located

A

In the fovea

55
Q

When are cones active

A

Brightly lit

56
Q

What are cones used for

A

Color vision

Sharp acuity

57
Q

What is the function of horizontal cells

A

Modulate signal from photoreceptor to bipolar cells

Inhibitory feedback to photoreceptors
Inhibitory feed-forward to bipolar cells

58
Q

Describe horizontal cells

A 
In outermost row of INL
Long axons
Several dendrites
Extend parallel to retina surface
Terminate in OPL
3 types
Release GABA
Communicate via gap junctions
59
Q

What is the function of retinal bipolar cells

A

2nd neuron in chain
Bridge outer and inner retina
Nuclei located in INL
Dendrites extend into OPL and synapse with photoreceptors and horizontal cells
Axons synapse with ganglion an amacrine cells in IPL
2 types

60
Q

What are the 2 types of retinal bipolar cells

A

Rod bipolar cells

Cone bipolar cells

61
Q

Describe rod bipolar cells

A

Only contact rods

Extend into OPL and synapse with rod spherule

62
Q

Where do rod bipolar cells first appear

A

In parafovea and present out to the far peripheral retina

63
Q

In the parafovea a single rod bipolar cell can synapse with ____ rods

A

15-20

64
Q

In the peripheral retina a single rod bipolar cell can synapse with ___ rods

A

80

65
Q

The axon of the rod bipolar cell extends into the _____ and forms the ______

A

IPL

Dyad

66
Q

Each dyad from a rod bipolar cell will contact what

A

A pair of A2 amacrine cell processes

67
Q

What NT is released from rod bipolar cells

A

Glutamate

68
Q

Describe cone bipolar cells

A

Contact only cones
12 subtypes
Categorized based on polarit of their response to light

69
Q

Axons of ON cone bipolar cells synapse with what

A

Dendrites of ganglion cells in sublamina B

70
Q

Axons of OFF cone bipolar cells synapse where

A

With dendrite of OFF ganglion cells in sublamina A

71
Q

What NT is released from cone bipolar cells

A

Glutamate

72
Q

Describe amacrine cells

A

Nuclei are found in innermost layer of the INL and sometimes GCL

40-50 types

73
Q

What is the function of amacrine cells

A

Modify signals in IPL

74
Q

What is the morphology of amacrine cells

A

Do not have axons

Have a single process that has branches and exhibits characteristics of both dendrites an axons

75
Q

What do amacrine cell processes synapse with

A

Processes of other amacrine cells,bipolar cells, interplexiform cells, retinal ganglion cells in IPL

76
Q

What are the 4 categories of the amacrine cells

A 
Narrow field (30-150 nm)
Small field (150-300 nm)
Medium field (300-500 nm)
Wide field (300-500 nm)
77
Q

What do amacrine cells detect

A 
Glycine
Dopamine
Serotonin
ACh
NO
Somatostatin
Substance P
Glucagon
GABA
Etc.
78
Q

What is the most widely studied amacrine cell

A

A2

79
Q

Describe A2 amacrine cells

A

Convey rod signal to retinal ganglion cells

Because rods have no direct contact with retinal ganglion cells

80
Q

Wiring

A

A2 amacrine cell transmits the rod signal from the rod bipolar cell to either an ON(gap Jen) of OFF cone bipolar cell(glycerine synapse) which influence their respective retinal ganglion cell.

81
Q

What are interplexiform cells

A

Interspersed with amacrine cells in innermost layer of INL

Send process to OPL and IPL

Carry feedback signals between the 2 layers

82
Q

What NT is released from interplexiform cells

A

GABA

Dopamine

83
Q

What are the 3 types of glial cells

A

Muller
Astrocytes
Microglia

84
Q

What are Muller cells

What are some functions

A

Radial glial cells
Provide structural support
Regulate K and glutamate concentrations, Make and store glycogen, proliferate in pathology

85
Q

Describe the morphology of Muller cells

A

Nuclei in INL
Span from ELM-ILM
Apical end is located in PRL and has microvilli
Basilar end has endfoor that helps make ILM
Zonula adherens attach adjacent distant processes of Muller cells

86
Q

What are astrocytes

A

Found in RNFL and RGCL
Star shaped
Surround and provide support to vasculature and axons in RNFL

87
Q

What are microglia

A

Found in small numbers in RNFL

Mobile phagocytes

88
Q

Look at slide 63

A

Yes

89
Q

How many retinal ganglion cells are in the retinal ganglion layer

A

1.2-2.2 million

90
Q

What do the axons of the retinal ganglia cells form

A

The retinal nerve fiber layer

91
Q

What neurotransmitter is released from the retinal ganglion cells

A

Glutamate

92
Q

How are retinal ganglion cells classifed

A

By the layer of lateral geniculate body

Parvocellular
Magnocellular

93
Q

Describe P cells

A

80%

Single dendrite projects into IPL ad synapses with a midget cone bipolar cells

94
Q

All info conveyed to a P cell is from

A

A single cone photoreceptor

95
Q

What do P cells allow for

A

Info related to color and high resolution

96
Q

Describe M cells

A

10%
Dendrites of M cells arborize in the IPL
Have wide dendritic fields that allow them to cover the entire retina

97
Q

What do M cells respond to

A

Moving or changing stimuli in the environment

98
Q

What is the retinal fiber layer composed of

A

Unmyleinated axons of retinal ganglion cells

Contains the superficial capillary plexus
Axons course parallel to retina surface where they converge to form optic disc

99
Q

What is the ILM

A

Innermost layer of retina
1-2 um thick
Basement membrane is formed by the end feet of Muller cells

Ocular Block 7 (9 decks)

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