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Cellular And Molecular > Lecture 8 - Retina And Vision > Flashcards

Lecture 8 - Retina And Vision Flashcards

1
Q

What do retina Contain?

A

Light sensitive cells

Photoreceptors, blue light sensitive RGCs

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2
Q

What else do retina Contain?

A

Neural network
Including bipolar, amacrine, horizontal cells
Output cells (retinal ganglion neurons) rhode axons form the optic nerve

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3
Q

How many major classes of neuron in the retina?

A

5

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4
Q

What does photoreceptors transduce?

A

Light

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5
Q

What makes synaptic connection onto a bipolar cells?

A

Cones

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6
Q

What are bipolar cells?

A

Special neuron in the retina

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7
Q

What connects from the photoreceptors to the retinal ganglion cells?

A

Bipolar cells

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8
Q

What is the vertical pathway?

A

Information flow through the retina

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9
Q

What layers are present on top of the retina where light strikes first?

A

Nerve fibre layer

Retinal ganglion cells

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10
Q

What must light go through to get to the light receptor cells?

A

All the neurophil

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11
Q

Where do you find almost 100% myelination?

A

Optic nerve

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12
Q

Where do nerve fibre become myelinated as they pass through the retina?

A

laminar cribosa

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13
Q

Why is axon with no myelin bad?

A

There is continuous conduction occurring in the axon

Obscures codon

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14
Q

What kind of axon are present in the visual system?

A

Myelinated and unmyelinated

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15
Q

What are horizontal cells?

A

Laterally interconnecting neurons

Cell bodies present in the inner nuclear layer of retina

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16
Q

What does horizontal cells help integrate and regulate?

A

Input from multiple photoreceptors cells

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17
Q

What does horizontal cells allow?

A

Eyes to adjust to see well under both bright and dim light conditions

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18
Q

What does horizontal cells provide?

A

Inhibitory feedback to rod and cone photoreceptor

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19
Q

What is photo pigment made from?

A

protein opsin

Derivative of vitamin A

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20
Q

What is protein opsin?

A

Encoded in our DNA

Protein that bind to light-reactive chemical to underlie vision

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21
Q

Derivative of vitamin A

A

Retinal

Exist in 2 isomers (cis/trans)

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22
Q

Several different … encoded by different genes

A

Opsins

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23
Q

Why is isomerization crucial?

A

When the retinal is in the cis form
It absorbs photons and changes into trans form
The whole complex transduces the photons that has been absorbed

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24
Q

In our light receptors called cones, how many different types of opsins present?

A

3

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25
What are the 3 receptors in the retina that are responsible for the perception of colour?
One receptor is sensitive to colour green Another blue Another red
26
What is the most common form of colour blindness?
The loss of ability to see green
27
What is trichromatic vision?
Sensitive to three of the colours Have perception of three primary colours Normal human vision
28
What happens when L is missing?
Unable to distinguish red from green
29
What is Rhodoxin sensitive to?
Low levels of light
30
What is Ishihara plate?
A classic device for testing colour blindness
31
What is a photomultiplier tube?
A photo emissive device in which the absorption of a photon results in the emission of an electron Sensitive to the arrival of photons As are retinal photoreceptors
32
What does photoreception allow?
Large amplification
33
What do we see in the output of retina?
Eigengrau ‘intrinsic light’ | See a foggy grey
34
What is the retina sensitive to?
Both light and dark
35
Which one has more activity in the retina?
Dark
36
What is a good stimuli for activating the human visual system?
Checker boards
37
What makes the 3 light sensitive system?
Rods Cones RGC blue light sensitive neurons
38
What is cones?
Evolutionarily older photoreceptors
39
What can Rods not able to respond to?
Light intensity fluctuations of 12Hz
40
What is present across the surface of retina?
Blood vessels
41
What does the neuron network and the photoreceptors require?
Oxygen
42
What is the optic cup?
White | Cup-like area in the centre of the optic disc
43
What is the optic disc?
The point in the eye where the optic nerve leaves the retina
44
What is the Fovea?
Located in the macula of the retina that provides the clearest vision of all Highest number of photoreceptors High density of cones High acuity and colour vision
45
What does retinal plan and light intensity fluctuation processing show?
basic vertical transfer of the information flow in the retina
46
What is light intensity fluctuation broken down into?
Separate frequency channels by the membrane properties of bipolar cells
47
What is band-pass filtering?
All information passes to RGCs via the bipolar cells
48
What can RGCs do?
Keep fluctuation frequency information separate and parallel Or recombine before sending to brain
49
What are vertebrate retinas dominated by?
rods
50
How many types of cones does FISH have?
4
51
What did primates re-evolve?
Trichromatic vision
52
What are cones
Not wavelength selective | Selective to white light over whole of visual spectrum
53
What are retinal ganglion cells?
1. On-centre, off-surround | 2. Off-centre, on-surround
54
What does retinal ganglion cells require?
Inhibitory horizontal and amacrine neurons
55
What does lateral inhibition highlight?
Intensity boundaries
56
What does Mach bands do?
Optical illusion Exaggerates the contrast between edges of the slightly differing shades of grey Triggers the edge-detection in the human visual system Illusion brought about by lateral inhibition
57
What did Herring postulate?
There was a light system and dark system | The balance between these antagonistic system gives us perceived light intensity
58
What is on-centre?
RGC responds to light
59
What is off-centre?
RGC responds when the light is switched off
60
What does retina have several types of?
RGC in an array covering entire field
61
What does the idea of antagonistic system impact?
Colour vision | Sensitivity to motion
62
What is how colours perceived based on?
Opponent colour theory
63
When does retinal ganglion cell give an output?
When you have a blue light shining on the centre of the surrounding inhibitory field
64
What is the blue cone doing?
Exciting the RGCs
65
What is the red and green cone doing?
Inhibiting
66
What may retinal ganglion cell sensitive to?
Yellow light | Receiving information from blue photoreceptor which is inhibitory
67
Retinal ganglion cells (yellow)
received information from red and green cones which are excitatory
68
What does the opponent colour theory suggest?
Colour perception is controlled by the activity of 2 opponent system: Blue-yellow mechanism Red-green mechanism
69
Surround inhibition
The network predicts what will be found in the centre of the field, and only when the illumination at the centre differs from what is predicted is a signal generated
70
What is reducing redundancy?
Sending only interesting or important information to the brain
71
What is the first relay point for visual information heading towards the cortex?
Retina | LGN nucleus
72
Where is the information passed to next?
``` Brodmann area 17 Striate Cortex (V1) ```
73
What does V1 have?
Neurons that are tuned to bars and edges moving or orientated in the correct way
74
Where does information from those cells (V1) go to?
Area 18 and 19 (V2 and V3)
75
What did Hubel and Wiesel (1962) study?
The effects of edges in the visual world and how edges were processed
76
What is orientation tubing a measure of?
How a cell is firing rate depends on the orientation of a stimulus
77
Why does amacrine cells have very long axons?
Bring information from a distant site on retina to our retinal ganglion cells where comparisons can be made It compares what is going on in the centre of vision with what is going on in the background
78
What is motion blindness?
Medical condition where a person cannot see objects that are moving even though they can see the objects that do not move Related to nerves
79
What is Melanopsin?
Retinal ganglion cells which are sensitive to blue light | Connect to SCN neuron
80
What 2 neurotransmitters do Melanopsin use?
Glutamate | Pituitary adenylate cyclase activating peptide (PACAP)
81
What does neurotransmitters affect?
The firing behaviour of SCN neuron
82
What happens when SCN neuron is excited by RGC?
An increase in calcium inside the SCN neuron Kinase activation CREB phosphorylation
83
What is CREB?
A protein that is activated by phosphorylation | Activates protein expression (gene expression)
84
What is E-box?
A region of DNA that is controlling whether this gene is going to be expressed
85
What is CRE?
Camp response element
86
What is PER expression?
Controls the expression of other proteins including that of C-B
87
SCN neuronal activity changes
Electrically silent at night Firing during the day Achieved through rhythmic changes in ion channel expression and phosphorylation

Cellular And Molecular (9 decks)

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