Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Optometry Class OP4102 > The Retina > Flashcards

The Retina Flashcards

(101 cards)

Start Studying
1
Q

why is the optic disk a blindspot?

A

as there are no photoreceptors in that area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the macula lutea?

A

a yellow spot on the retina that’s due to an accumulation of retinal carotenoids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

give the 11 layers of the retina

A
  1. ILM: inner limiting membrane
  2. NFL: nerve fibre layer
  3. GCL: ganglion cell layer
  4. IPL: inner plexiform layer
  5. INL: inner nuclear layer
  6. OPL: outer plexiform layer
  7. ONL: outer nuclear layer
  8. OLM: outer limiting membrane
  9. is: photoreceptors innersegments
  10. os: photoreceptors outersegments
  11. RPE: retinal pigmentepithelium

If Nans Go In Iceland Or Other Outings Phone Papa Really

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the three neurones in the retina?

A
  1. ganglion cells
  2. bipolar cells
  3. photoreceptor cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the features of the internal limiting membrane?

A

-mainly composed of basement membrane formed by muller cell footplate processes
-occasionally astrocyte processes and consist of broad flat cells containing rod shaped nuclei
-ILM has the vitreous attached through fine collagen fibrils
-normally absent over the optic nerve head

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the layers of the ganglion of the ILM?

A

-Nerve fibre layer - Axons of retinal ganglion cells -(RGCs)+ a few neuroglial cells (astrocytes =astroglia and microglia)
-Ganglion Cell Layer- Retinal ganglion cell (RGC)bodies and some amacrine cell bodies Inner
-Plexiform Layer- Axons and dendrites: synapses of bipolar cells and amacrine cells with ganglion cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the layers of the bipolar layer of the ILM?

A

-inner nuclear layer: consists of the cell bodies of nueornes (amacrine, bipolar and horizontal cells) and muller cells
-outer plexiform layer: synapses of photoreceptor cells with bipolar and horizontal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the layers of the photoreceptor layer of the ILM

A

-outer nuclear layer whicnb has 8-9 layers of of densly packed nuclei and cell bodies of the rods and cones but rods have smaller nucei while cones have larger nuclei that reside just internal to the external limiting membrane
-external outer limiting membrane (not an actual membrane) - where zonula and macula adherens connect muller cells with photoreceptor inner segments that connect muller cells with

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe the features of the inner segment of a photoreceptor

A

-it extends beyond the external limiting membrane
-ER for protein and lipid synthesis, golgi for carb synthesis and protien modification
-cone inner segment, larger than in rods and contains numerous mitochondria
-rod inner segment is cylindrical and fewer mitochondria than in cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what do photoreceptor cilia consist of? what are they for? when are they dysfunctional?

A

-inner and outer segment connected by a modified cilium
-nine doublet microtubules with no central microtubules
-important in transfer of molecules
-often dysfunctional in ushers syndrome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the two parts of the photoreceptor outer segments and what do they consist of?

A

-Rod OS: stacked disks separated from the plasma membrane
-Cone OS stacked disks continuous with the plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

give four features of rod disks in the outer segment

A

-contains 600-1000 stacked disks
-connected to plasma membrane but its not continuous with it
-2 micrometers in diameter
-rhodopsin molecules are located within disc membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what two types of epithelium does the RPE consist of?

A

-simple cuboidal epithelium: a monolayer of regularly arranged hexagonal cells
-simple columnar epithelium over the fovea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is the RPE highly polarised?

A

due to the zonulae occuludentes ( tight junctions )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

whys the RPE so important?

A

provides the blood brain barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the cartenoids that comprise the macular pigment in the macula lutea?

A

carotenoids:
-meso zeaxanthin
-lutein
-zeaxanthin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the use of the macula lutea?

A

the macular pigment heightens absorption of blue light so enhances visual resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what does the central retina contain?

A

the macula which consists of
-fovea centralis
-foveola
-parafovea
-peri fovea
-optic disk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does the apical surface of the RPE contain?

A

microvilli bathed in the interphotoreceptor matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does the basal surface of the RPE contain?

A

infoldings at the basal surface that increase its surface area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

give the steps in transport, synthesis, recycling, and storage in the rpe

A
  1. Diffusion/uptake of oxygen and nutrients from blood
  2. Uptake and storage of nutrients and micronutrients (including vitamin A), and their transformations
  3. Transport of nutrients and 11-cis-retinal to photoreceptors
  4. Regulating flow of water and other molecules by tight junctions (gate and fence function); providing the blood-retina barrier
  5. Phagocytosis of tips of photoreceptor outer segments(POS)
  6. Recycling of proteins, lipids, and vitamin A from phagocytosed and degraded POS
  7. Removal of waste products to the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what happens to the oxygen conc of cone cells in the dark

A

the oxygen concentration becomes close to zero in the inner segment layer as the oxygen use is very high in the dark

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

which inner segment between cones and rods contains more mitochondria?

A

cone inner segment and hence it has a larger inner segment than rods because in the dark, the cones have a high oxygen consumption so theres a constant need to receive oxygen and nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

give the cation channels in the outer segment of photoreceptors

A

-Na/ K, Ca exchanger
-cGMP - gated channel due to influx of Na+ and Ca+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
give the cation channels in the inner segment of photoreceptors
-potassium channels -ATP dependent Na-K pumps responsible for the constant circulation of ions in the dark
26
what are omega 3 lipids for in rod disks? what is it called?
-provides high fluidity to the lipid membrane as deficiency causes impairment of learning and memory -docosahexaenoate (DHA)
27
what's the difference in length between rod and cone cells?
rods have long outer segments that reach the RPE while cones have a shorter outer segment so send microvilli to encompass the cone outer segments
28
what happens in the phagocytosis of photoreceptor outer segments by the RPE in three steps
1. disc shedding 2. phagocytosis 3. lysosomal degradation
29
in a sequence, how does the RPE have a role in providing 11-cis-retinal the chromophore of visual pigments? (retina 2 for relevence)
1. uptake of vitamin A ( all trans retinol) from the blood 2. uptake of vitamin a from the interphotoreceptor matrix 3. intracellular transport of retinoids by the cellular retinoid binding protein and the cellular retinal binidng protein 4. esterification of vitamin A with fatty acids by lecithin retinol acetyl transferase to form retinyl esters 5. storage of retinyl esters 6. synthesis of 11-cis retinal to form all trans retinyl esters 7. transport of 11-cis-retinal to photoreceptor outer segments
30
why does the fundus appear as the darker area in the fovea?
due to increased melanin in the RPE
31
where is melanin synthesised?
in the protein matrix of melanosomes
32
which optic layer doesn't disappear in the optic disk?
the nerve fibre layer
33
what does the fovea mainly consist of and what is the ratio of photoreceptors, bipolar and ganglion cells and why is it that?
Mainly cones with specialised architecture that resembles rods, 1:1:1 and this is to enhance the resolution of spatial and temporal simulation
34
what is the maximal retinal thickness?
349+- 17 micrometers
35
compare the number of cones and rod
rods: 78-125 million/ retina cones: 5.6-6.8 million/retina
36
what part of the retina is the density of cones highest?
in the fovea
37
in what part of the retina is the density of cones the least?
temporal periphery side
38
what is the parafovea?
a 0.5mm ring surrounding the fovea and has the largest density of ganglion and bipolar cells
39
what is the perifovea?
a 1.5mm ring surrounding the parafovea with less ganglion cells than the parafovea
40
what is the peripheral retina?
a mostly single cell layer of ganglion cells outside the macula
41
Give a brief sequence of phototransduction in photoreceptor neurons in 3 steps
1. absorption of a photon 2. hyperpolarisation of plasma membrane 3. release of the neurotransmitter of glutamate is inhibited
42
watch the khan academy video on phototransduction in photoreceptors
ok
43
give the sequence of events in the phototransduction cascade
1. visual pigment is activated - rhodopsin in rods 2. activation of transducin 3. activation of phosphodiesterase (PDE) 4. degredation of cGMP to GMP 5. closure of cCMP gated channels 6. Na+ decreases and Ca2+ decreases -plasma membrane is hyperpolarised
44
how is the yield of photoactivation of rhodopsin very high?
every 2 out of 3 absorbed photons leads to photoactivation of rhodopsin
45
what are rods and cones in terms of day and night vision?
rods: scotopic - night cones: photopic - day
46
in the phototransduction cascade at the end, how does the release of glutamate get inhibited?
1. hyperpolarization of plasma membrane spreads to the synaptic terminal 2. voltage-dependent Ca2+ channels in the synaptic terminal close 3. the influx of Ca2+ is decreased 4. this inhibits glutamate as Ca2+ is needed for fusion of neurotransmitter-carrying vesicles with the plasma membrane
47
what are the 4 types of bipolar cells and what do they do?
-rod bipolars: connect up to 50 rods, connect ~4 ganglion cells -S-cone cells -Midget bipolars: join one cone with one ganglion cell, foveal -diffuse bipolars: widespread synaptic connections (up to 7 cones) and many ganglion cells, excitatory or inhibitory, hyperpolarising or depolarising
48
What are horizontal cells?
synaptic connections with photoreceptors that hyperpolarize in response to light and release the inhibitory neurotransmitter GABA to provide feedback to cones in gap junctions
49
what are the three different types of horizontal cells and what do they connect to from each side?
HI- The dendritic arbour connects with S,M and L cones and the axonal arbour connects with rods HII- the dendritic arbour connects to S cone and the axonal arbours connect with S, M and L cones HII -the dendritic arbour connects with L and M cones and the axonal arbour connects with L and M cones
50
give three types of amacrine cells
starburst, dopaminergic and A1
51
what do amacrine cells receive from and where do they send messages to?
receive from bipolar cells and other amacrine cells and they send messages to bipolar cells, amacrine cells and ganglion cells
52
at least how many types of retinal ganglion cells are there?
at least 25 different types
53
where are most of the cell bodies of amacrine cells present?
the nuclear cell layer
54
what are the 4 retinal ganglion cells?
-parasol -midget -blue-yellow -biplexiform
55
what type are the majority of RGCs and what do they receive from?
midget RGCs as they make up 70% of RGCs in the retina and they recieve from midget bipolars
56
what % of RGCs do parasol make up and what do they receive from?
8-10% and they receive from diffuse bipolars
57
what are photosensitive RGCs?
a small subset of RGCs that express melanopsin and are responsible for photoentrainment and pupillary light reflex
58
what are the characteristics of RGCs axons in the nerve fibre layer of the retina?
-connected to the optic disk -unmyelinated -eneveloped by extensions of muller cells and astrocytes
59
how is visual prosthesis possible? What does it do?
the ordered arrangement of axons and retinal ganglion cells as an electrode can directly stimulate the axons at the end of the optic disk and so can help restore vision in patients with total visual loss due to retinitis pigmentosa as well as AMD
60
what are the three types of cones and their corresponding colours and what are each of their wavelengths they are best responsive to?
- S cones: blue - 437nm -M cones: green - 533nm -L cones: red - 564nm
61
what colour are red cones most responsive to and how are they different to the other cones?
yellow light and unlike others they maintain their responsiveness to light for longer and hence do still respond well to red light
62
for S cones, where is their density lowest, where do they reach max density and what percentage of the total cone population do they make up elsewhere
-lowest density in the foveal pit at 3-5% -reach max density in the foveal slope at 15% -8%
63
why does perception of blue light reduce as you age?
as a result of the macular pigment that covers the fovea as well as the low density of S cones on the fovea.
64
why does the perception of colour change in age?
As the crystalline lens yellows
65
How is phototransduction de-activated?
1. deactivation of visual pigment of rhodopsin 2. deactivation of transducin 3. deactivation of phosphodiesterase 4. synthesis cGMP increasing it's conc again 5. cGMP-gated channels reopen 6. cytoplasmic conc. of Ca2+ increases again 7. translocation of arresting and transducin 8. recovery of all visual pigments through the retinoid cycle 9. recovery of the maximal gains of the amplification
66
How is rhodopsin deactivated?
1. GTP-ase activity of activated rhodopsin by rhodopsin kinase 2. binding of arrestin to disable metarhodopsin II from activating transducins
67
How is phosphodiesterase (PDE) deactivated? what happens next?
1. GTP-ase transducin alpha bound to gamma PDE converts GTP into GDP 2. this causes transducin alpha bound GDP to dissociate from PDE and hence deactivating it cGMP molecules are then synthesised by guanylate cyclase activated by GC activating protein and this then converts GTP nucleotides into cyclic GMP by formation of phosphodiester bonds. cGMP gated channels are re-opned due to increased affinity for cGMP and increased concentration of cGMP
68
what is the concentration of Ca2+ like during the deactivation of phototransduction?
low because this makes it easier for PDE to dissociate from transducin GDP
69
By how much does light intensity change in the environment that our vision functions?
in the environment where light intensity changes by over 11 orders of magnitude due how photoreceptors have adapted to ambient light
70
how does adaption of photoreceptors to ambient light affect photosensitivity? Why is this?
By causing photosensitivity to decrease which is approximately in inverse proportion to the intensity of the ambient light. This is due to a decreased gain in amplification
71
What are the amplification steps in the phototransduction cascade for light adaptation?
1. light absorption closes cGMP gated channels 2. internal Ca2+ decreases 3. cGMP production increases and channel affinity increases 4. some of the closed channels re-open 5. photocurrent decreases towards the baseline
72
what is dark adaptation?
the recovery of all visual pigments and the maximal sensitivity of photoreceptors in the dark
73
what mechanism is required for dark adaptation?
termination of the phototransduction cascade
74
what do opsins do?
they activate the phototransduction cascade without chromophore so photoreceptors in the dark behave as if they were exposed to background light
75
what is Stargrdt's disease caused by and what does it lead to?
caused by dysfunction in ABCR protein leading to accumulation of toxic all-trans-retinal causing RPE dysfunction and photoreceptor death
75
what is the interphotoreceptor matrix (IPM) composed of?
-enzymes responsible for IPM turnover for example MMPs and TIMPs which are tissue inhibitors of MMPs -proteoglycans -glycoproteins -GAGs -IRBP (interphotoreceptor retinoid binding protein)
76
what cells is the IPM specific to?
rods and cones
77
what are the steps in the retinoid cycle?
first of all, vitamin A (all-trans -retinol) is taken up from the blood and this then gets taken up from the interphotoreceptor matric 1. transport by cellular retinoid binding protein (CRBP) 2. esterification by lecithin retinol acyl transferase (LRAT) with fatty acids 3. human stores of retinyl esters in the RPE are enough to regenerate 2.5 mol eq of rhodopsin 4. isomer hydrolase isomerises and hydrolyses all-trans-retinyl esters to 11-cis-retinol 5. oxidation of 11-cis-retinol to 11-cis-retinal by 11-cis-retinol dehydrogenase 6. transport of 11 cis retinal by cellular retinal binding protein (CRALBP)
78
what is leber's congenital amaurosis and what is it caused by?
rapid loss of vision in childhood or young adulthood due to loss of photoreceptors , caused as a result of the dysfunctional protein RPE65 which leads to the inability of synthesis of 11-cis-retinal
79
how can LCA be treated with gene therapy?
by delivering RPE65 with adeno associated virus AAV2 as the vector using an RPE specific promoter to restrict the expression of the RPE transgene only to the RPE cell layer
80
how can LCA be treated pharmacologically?
supplementation with 9-cis-retinal to enable synthesis of visual pigments
81
how long does cone and rod pigment to regenerate?
-cone pigment takes 10 minutes -rod pigment takes 20-30 minutes
82
why do cones regenerate visual pigment faster than rods?
because muller cells synthesize 11-cis-retinol from all-trans-retinol. only cones can convert 11-cis-retinol to 11-cis-retinal
83
what pigments are responsible for the fovea and its surrounding area to appear yellow?
-lutein -caroteinoid -xanthophyll -macular pigment
84
what connects photoreceptor inner segment with outer segment?
a modified cilium
85
What happens to the circulating ion current in photoreceptors in response to absorption of light?
its value increases and its absolute value decreases
86
what is the plasma membrane potential of photoreceptors in the dark?
About -35mV
87
compare the maximum sensitivity for scotopic and photopic vision
they are the same
88
what neurotransmitter is released from photoreceptors in the dark?
glutamate
89
what happens to bipolar cells in synaptic contact with a hyperpolarized cone?
some depolarize while others hyperpolarise
90
what cells in the retina are specialised for setting our circadian clock and pupillary light reflex but not visual perception?
ganglion cells expressing an opsin based pigment
91
give 4 reasons for the high concentration of docosahexanoate in the retina
-to facilitate changes of conformation of transmembrane receptor proteins -to allow activation of rhodopsin -to facilitate regeneration of visual pigment -to increase fluidity of the disk membrane
92
How is info about the absorption of photons in the retina passed on to the brain via ganglion cell axons?
via changes in frequency of generation of action potentials by the ganglion cells
93
what is an approximate concentration of calcium ions in the cytoplasm of rods adapted to saturated light?
60nmol/L
94
what is the concentration of calcium in the rod cytoplasm in dark?
600nM
95
what is the role of rhodopsin kinase in deactivation of phototransduction?
phosphorylation of metarhodopsin II
96
what is the function of muller cells in recovery of the dark-adapted state of photoreceptors?
they convert all-trans-retinol to 11-cis-retinol to facilitate generation of visual pigments in cones
97
what is the limiting step in regeneration of high sensitivity of photoreceptors in the healthy human eye in the dark?
synthesis of 11-cis-retinal for regeneration of rhodopsin
98
How long does it take the retina to recover the highest sensitivity to light after exposure to bright light bleaching more than 90% of rhodopsin?
more than half an hour
99
give 4 events responsible for adaptation of photoreceptors to the dark
-influx of calcium to photoreceptor inner segments -termination of phototransduction cascade -regeneration of visual pigemnts -synthesis of 11-cis-retinal
100
what is the role of RPE65 protein in synthesis of 11-cis-retinal
it is responsible for the isomeration and hydrolysis of all-trans-retinyl esters

Optometry Class OP4102 (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions