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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
What is the rod spherule
Synaptic terminal of rod | Contains mitochondria, vesicles, microtubules
26
What is the triad of the rod spherule
Process from the horizontal cells and dendrites from rod bipolar cells invaginate
27
How many triads does a rod spherule have
1
28
How many rods are there
92-120 million
29
When are rods active
In dim conditions
30
Where does the rod density peak at
18 degrees from the center of the fovea
31
Where are there NO cones
In the fovea
32
What makes up the discs in the cone What affect does this have
Invagination of the plasma membrane The discs are in contact with extracellular environment
33
What are the 3 opsins of the cones
S(blue) 488 nm M(green) 531 nm L(red) 588 nm
34
What is dichromacy
When one of the 3 cone photopigments is absent and color is reduced to 2 dimension
35
What are th categories of dichromate
Protanope Deuteranope Tritanope
36
Protanopes lack
L cones
37
Deuteranopes lack
M cones
38
Tritanopes lack
S cone
39
Protanopes have a ______ problem discriminating ______
Severe | Red-greens
40
Deuteranopes have a ____ discriminating ______
Mild Red-green
41
Tritanopes have a hard time discriminating
Blue green | Yellow-pink
42
What is the function of the connecting cilum in cones
Connect the outer and inner segment of the cones
43
How does the inner segment of the cone differ from the rods
Ellipsoid region is much broader and contains greater number of mitochondria
44
How does the outer fiber of the cone differ from the rods
Very short and sometimes absent
45
Describe the cone cell body
Monolayer In outermost layer of ONL Occupy all rows in ONL Larger than in rods
46
What is the function of the inner fiber in cones
Axon Has microtubules Extends from cell body to pedicle in OPL
47
Cone fibers that are oriented obliquely in the fovea are called this
Henle fibers | OPL in the fovea is known as Henle's fiber layer
48
What is the equivalent of the cone pedicle in rods
Spherule
49
What is the pedicle of the cones
Synaptic terminal | Has mitochondria, synaptic vesicles, microtubules
50
What forms the triad in cone pedicle
Invaginating midget cone bipolar cells
51
Each pedicle has how many ribbons and triads
30 ribbons | 30 triads
52
What neurotransmitter is released from cones
Glutamate
53
How many cones are there
5-6 million
54
Where are 10% of the cones located
In the fovea
55
When are cones active
Brightly lit
56
What are cones used for
Color vision | Sharp acuity
57
What is the function of horizontal cells
Modulate signal from photoreceptor to bipolar cells Inhibitory feedback to photoreceptors Inhibitory feed-forward to bipolar cells
58
Describe horizontal cells
``` 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
What is the function of retinal bipolar cells
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
What are the 2 types of retinal bipolar cells
Rod bipolar cells | Cone bipolar cells
61
Describe rod bipolar cells
Only contact rods | Extend into OPL and synapse with rod spherule
62
Where do rod bipolar cells first appear
In parafovea and present out to the far peripheral retina
63
In the parafovea a single rod bipolar cell can synapse with ____ rods
15-20
64
In the peripheral retina a single rod bipolar cell can synapse with ___ rods
80
65
The axon of the rod bipolar cell extends into the _____ and forms the ______
IPL | Dyad
66
Each dyad from a rod bipolar cell will contact what
A pair of A2 amacrine cell processes
67
What NT is released from rod bipolar cells
Glutamate
68
Describe cone bipolar cells
Contact only cones 12 subtypes Categorized based on polarit of their response to light
69
Axons of ON cone bipolar cells synapse with what
Dendrites of ganglion cells in sublamina B
70
Axons of OFF cone bipolar cells synapse where
With dendrite of OFF ganglion cells in sublamina A
71
What NT is released from cone bipolar cells
Glutamate
72
Describe amacrine cells
Nuclei are found in innermost layer of the INL and sometimes GCL 40-50 types
73
What is the function of amacrine cells
Modify signals in IPL
74
What is the morphology of amacrine cells
Do not have axons | Have a single process that has branches and exhibits characteristics of both dendrites an axons
75
What do amacrine cell processes synapse with
Processes of other amacrine cells,bipolar cells, interplexiform cells, retinal ganglion cells in IPL
76
What are the 4 categories of the amacrine cells
``` Narrow field (30-150 nm) Small field (150-300 nm) Medium field (300-500 nm) Wide field (300-500 nm) ```
77
What do amacrine cells detect
``` Glycine Dopamine Serotonin ACh NO Somatostatin Substance P Glucagon GABA Etc. ```
78
What is the most widely studied amacrine cell
A2
79
Describe A2 amacrine cells
Convey rod signal to retinal ganglion cells | Because rods have no direct contact with retinal ganglion cells
80
Wiring
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
What are interplexiform cells
Interspersed with amacrine cells in innermost layer of INL Send process to OPL and IPL Carry feedback signals between the 2 layers
82
What NT is released from interplexiform cells
GABA | Dopamine
83
What are the 3 types of glial cells
Muller Astrocytes Microglia
84
What are Muller cells | What are some functions
Radial glial cells Provide structural support Regulate K and glutamate concentrations, Make and store glycogen, proliferate in pathology
85
Describe the morphology of Muller cells
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
What are astrocytes
Found in RNFL and RGCL Star shaped Surround and provide support to vasculature and axons in RNFL
87
What are microglia
Found in small numbers in RNFL | Mobile phagocytes
88
Look at slide 63
Yes
89
How many retinal ganglion cells are in the retinal ganglion layer
1.2-2.2 million
90
What do the axons of the retinal ganglia cells form
The retinal nerve fiber layer
91
What neurotransmitter is released from the retinal ganglion cells
Glutamate
92
How are retinal ganglion cells classifed
By the layer of lateral geniculate body Parvocellular Magnocellular
93
Describe P cells
80% | Single dendrite projects into IPL ad synapses with a midget cone bipolar cells
94
All info conveyed to a P cell is from
A single cone photoreceptor
95
What do P cells allow for
Info related to color and high resolution
96
Describe M cells
10% Dendrites of M cells arborize in the IPL Have wide dendritic fields that allow them to cover the entire retina
97
What do M cells respond to
Moving or changing stimuli in the environment
98
What is the retinal fiber layer composed of
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
What is the ILM
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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