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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
Q

What are the 3 receptors in the retina that are responsible for the perception of colour?

A

One receptor is sensitive to colour green
Another blue
Another red

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26
Q

What is the most common form of colour blindness?

A

The loss of ability to see green

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27
Q

What is trichromatic vision?

A

Sensitive to three of the colours
Have perception of three primary colours
Normal human vision

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28
Q

What happens when L is missing?

A

Unable to distinguish red from green

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29
Q

What is Rhodoxin sensitive to?

A

Low levels of light

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30
Q

What is Ishihara plate?

A

A classic device for testing colour blindness

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31
Q

What is a photomultiplier tube?

A

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

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32
Q

What does photoreception allow?

A

Large amplification

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33
Q

What do we see in the output of retina?

A

Eigengrau ‘intrinsic light’

See a foggy grey

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34
Q

What is the retina sensitive to?

A

Both light and dark

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35
Q

Which one has more activity in the retina?

A

Dark

36
Q

What is a good stimuli for activating the human visual system?

A

Checker boards

37
Q

What makes the 3 light sensitive system?

A

Rods
Cones
RGC blue light sensitive neurons

38
Q

What is cones?

A

Evolutionarily older photoreceptors

39
Q

What can Rods not able to respond to?

A

Light intensity fluctuations of 12Hz

40
Q

What is present across the surface of retina?

A

Blood vessels

41
Q

What does the neuron network and the photoreceptors require?

A

Oxygen

42
Q

What is the optic cup?

A

White

Cup-like area in the centre of the optic disc

43
Q

What is the optic disc?

A

The point in the eye where the optic nerve leaves the retina

44
Q

What is the Fovea?

A

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
Q

What does retinal plan and light intensity fluctuation processing show?

A

basic vertical transfer of the information flow in the retina

46
Q

What is light intensity fluctuation broken down into?

A

Separate frequency channels by the membrane properties of bipolar cells

47
Q

What is band-pass filtering?

A

All information passes to RGCs via the bipolar cells

48
Q

What can RGCs do?

A

Keep fluctuation frequency information separate and parallel
Or recombine before sending to brain

49
Q

What are vertebrate retinas dominated by?

A

rods

50
Q

How many types of cones does FISH have?

A

4

51
Q

What did primates re-evolve?

A

Trichromatic vision

52
Q

What are cones

A

Not wavelength selective

Selective to white light over whole of visual spectrum

53
Q

What are retinal ganglion cells?

A
  1. On-centre, off-surround

2. Off-centre, on-surround

54
Q

What does retinal ganglion cells require?

A

Inhibitory horizontal and amacrine neurons

55
Q

What does lateral inhibition highlight?

A

Intensity boundaries

56
Q

What does Mach bands do?

A

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
Q

What did Herring postulate?

A

There was a light system and dark system

The balance between these antagonistic system gives us perceived light intensity

58
Q

What is on-centre?

A

RGC responds to light

59
Q

What is off-centre?

A

RGC responds when the light is switched off

60
Q

What does retina have several types of?

A

RGC in an array covering entire field

61
Q

What does the idea of antagonistic system impact?

A

Colour vision

Sensitivity to motion

62
Q

What is how colours perceived based on?

A

Opponent colour theory

63
Q

When does retinal ganglion cell give an output?

A

When you have a blue light shining on the centre of the surrounding inhibitory field

64
Q

What is the blue cone doing?

A

Exciting the RGCs

65
Q

What is the red and green cone doing?

A

Inhibiting

66
Q

What may retinal ganglion cell sensitive to?

A

Yellow light

Receiving information from blue photoreceptor which is inhibitory

67
Q

Retinal ganglion cells (yellow)

A

received information from red and green cones which are excitatory

68
Q

What does the opponent colour theory suggest?

A

Colour perception is controlled by the activity of 2 opponent system:
Blue-yellow mechanism
Red-green mechanism

69
Q

Surround inhibition

A

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
Q

What is reducing redundancy?

A

Sending only interesting or important information to the brain

71
Q

What is the first relay point for visual information heading towards the cortex?

A

Retina

LGN nucleus

72
Q

Where is the information passed to next?

A 
Brodmann area 17 
Striate Cortex (V1)
73
Q

What does V1 have?

A

Neurons that are tuned to bars and edges moving or orientated in the correct way

74
Q

Where does information from those cells (V1) go to?

A

Area 18 and 19 (V2 and V3)

75
Q

What did Hubel and Wiesel (1962) study?

A

The effects of edges in the visual world and how edges were processed

76
Q

What is orientation tubing a measure of?

A

How a cell is firing rate depends on the orientation of a stimulus

77
Q

Why does amacrine cells have very long axons?

A

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
Q

What is motion blindness?

A

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
Q

What is Melanopsin?

A

Retinal ganglion cells which are sensitive to blue light

Connect to SCN neuron

80
Q

What 2 neurotransmitters do Melanopsin use?

A

Glutamate

Pituitary adenylate cyclase activating peptide (PACAP)

81
Q

What does neurotransmitters affect?

A

The firing behaviour of SCN neuron

82
Q

What happens when SCN neuron is excited by RGC?

A

An increase in calcium inside the SCN neuron
Kinase activation
CREB phosphorylation

83
Q

What is CREB?

A

A protein that is activated by phosphorylation

Activates protein expression (gene expression)

84
Q

What is E-box?

A

A region of DNA that is controlling whether this gene is going to be expressed

85
Q

What is CRE?

A

Camp response element

86
Q

What is PER expression?

A

Controls the expression of other proteins including that of C-B

87
Q

SCN neuronal activity changes

A

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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