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hybw > L5 Seeing things: the retina part > Flashcards

L5 Seeing things: the retina part Flashcards

1
Q

Only ___ of the human eyeball is exposed.

A

1/6

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2
Q

The eye muscles are the most ____ muscles in the human body.

A

active

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3
Q

An iris has _____ unique characteristics

A

256

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4
Q

Eyes are the _____ most _____ organ in body

A

second; complex

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5
Q

1 eye has ___ blind spot

A

one

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6
Q

The human eye only see three colours, ________

A

red, green, blue

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7
Q

Colour blindness is more common in ______

A

males

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8
Q

There are around ______ million blind people in the world, and ____% of vision problems worldwide are avoidable/ curable

A

39; 80

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9
Q

The total retina is a __________ of between ____ and ____ mm in diameter

A

circular disc; 30; 40

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10
Q

Area of the human retina is about _____ square cm

A

10

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11
Q

Sclera is a _____ & _____ tissue

A

tough; elastic

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12
Q

What does sclera do?

A

avoid the eye from expanding from the pressure

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13
Q

What does choroid do?

A

provide oxygen and nutrition to the retina

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14
Q

What does retina do?

A

Neuronal tissue that can convert light signal and send to the brain

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15
Q

How does the posterior segment maintain the round shape?

A

The gel-like fluid w/ intraocular fluid

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16
Q

What only goes out from the optic nerve, but not in?

A

Axons of output neurons

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17
Q

What goes in and out from the optic nerve head?

A

Blood vessels

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18
Q

Which part of the eye has the highest acuity vision?

A

Fovea

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19
Q

Why there is a blind spot?

A

There is an optic nerve head in our eyeball

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20
Q

Which part also provide us high acuity vision?

A

Macular

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21
Q

Which part is the thinnest place in retina?

A

Fovea

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22
Q

What is the thickness of retina?

A

200 millimetres thick

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23
Q

The ________ shows greatest variations in the center.

A

Retinal thickness

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24
Q

The retina is thinnest at the _______ and thickest at the _________

A

foveal floor; foveal rim

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25
Q

Beyond the fovea, the retina rapidly thins until the _____

A

equator

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26
Q

Outer plexiform layer is where the _________ and the ________ of the other inter neurons meet

A

axons of the photoreceptor cells; dendrites

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27
Q

Inner plexiform layer is where the ________ meet with __________

A

axons of the inner neurons; ganglion cell dendrites

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28
Q

Nerve fibre layer is where ___________, stack up and ______ and growing towards the _________, all go out

A

axons of all the ganglion cells; pointing; optic nerve head

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29
Q

________ layer -> inner ______ layer -> inner _______ layer -> outer ______ layer -> outer _______ layer

A

ganglion cell; plexiform; nuclear; plexiform; nuclear

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30
Q

The retina is composed of ______ major cell types that are arranged in _____ cellular layer (_____) separated by two ______ layers (_____)

A

five; three; GCL, INL, ONL; synaptic; IPL, OPL

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31
Q

What are the photoreceptors?

A

Cones and rods

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32
Q

Where is horizontal cell found?

A

At the border between the outer plexiform layer and the inner nuclear layer

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33
Q

Where is amacrine cell found?

A

Inner nuclear layer connect to inner plexiform layer

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34
Q

Where is ganglion cell found?

A

Ganglion cell layer

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35
Q

Which is the only output cell?

A

Ganglion cell

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36
Q

Lateral information flow is to contact ______ & _____ and modify their ________

A

bipolar cells; ganglion cells; signal transduction

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37
Q

Dendrites of horizontal cells contact with _______ & ______, to modify the signals that’s transmitted from ________ out to ________

A

photoreceptor; bipolar cells; photoreceptor; bipolar cells

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38
Q

Which layer is the outermost layer?

A

Photoreceptor cells

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39
Q

What does the photoreceptor cells do?

A

Absorb light & convert it into neuronal signal (phototransduction)

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40
Q

Neuronal signals from photoreceptor cells are passed _______ to ________, which in turn connect to ____________ in the ________ layer.

A

synaptically; bipolar cells; retinal ganglion cells; innermost

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41
Q

Bipolar neurons transmit information _______ (along the light path)

A

vertically

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42
Q

There are many lateral connections provided by __________ & _________ and they transmit information ________ (______ to light path)

A

horizontal cells; amacrine cells; sideways; perpendicular

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43
Q

Horizontal & amacrine cells mostly provide _______ and to ______ so that we can extract the most important info from what we see

A

modification; process information

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44
Q

______ are the output neurons of the retina

A

Retinal ganglion cells

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45
Q

The retina (the whole circuit) performs ____________

A

low-level visual processing

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46
Q

Retina extracts from the raw images in the left and right eyes certain _______ & ________ features and conveys them to ________

A

spatial; temporal; higher visual centers

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47
Q

What does horizontal cells do?

A

Regulate and integrate signals from photoreceptor to bipolar

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48
Q

What does amacrine cells do?

A

Regulate and integrate signal from bipolar to ganglion cells & modify signal transduction

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49
Q

Rods and cones differ in ______ and more importantly in _______

A

morphology; function

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50
Q

What can rod do?

A

Signal the absorption of a single photon

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51
Q

What is rod responsible for?

A

Vision under dim illustration

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52
Q

Which cell is less sensitive to light?

A

Cones

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53
Q

What is cone responsible for?

A

Vision in daylight

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54
Q

Which photoreceptor is considerably faster?

A

Cones

55
Q

Human retina contains approximately ____ rods and _____ cones

A

110 million; 6 million

56
Q

Rods and cones are NOT equally distributed, in most part of the retina, the _____ predominate, outnumbering the ____ by some of _____ to ___

A

Rods; cones; 10; 1

57
Q

Fovea only have _____ (photoreceptor)

A

Cones

58
Q

Which photoreceptors can see colour?

A

Cones

59
Q

Which photoreceptors have higher acuity?

A

Cones

60
Q

Light comes, hit one of the ____, activate _______

A

light sensing proteins; signal transduction

61
Q

Which part of the photoreceptors is the energy factory of neurons?

A

Inner segment

62
Q

How ATP is used in photoreceptors? Why?

A

To maintain its membrane potential because photoreceptors are very high energy demanding

63
Q

Why need many membrane discs?

A

On each membrane discs, there are many light sensing proteins and they are transmembrane proteins, so they need membrane surface to be inserted there

64
Q

What does the membrane disc morphology do?

A

helps to maximize the surface areas so that we can more light sensing proteins in one place

65
Q

Cats are nocturnal so they have ___ to ___ times as many ____ for viewing objects in low light as humans. They also have better _____ vision

A

6; 8; rods; peripheral

66
Q

Humans have more ____, which provides us much more ___ palette of colour and __ acuity

A

cones; vibrant; higher

67
Q

In the fovea, corresponding to the very center gaze, the ____ is shifted aside so light has a direct access to the ______

A

Proximal neurons; photoreceptors

68
Q

The cones are highly concentrated at the _____, an area of just ____. This region is responsible for our ______ vision and could be regarded as the most important square milimeter in our body

A

fovea; 1 square milimeter; high-acuity colour

69
Q

_____ does not have rods, so it is ____

A

Fovea; night blind

70
Q

There is a limit in our ______, so if looking at a device which has a higher resolution than our _______, we can’t distinguish

A

retina; retinal resolution

71
Q

In which part are the interneurons and ganglion cells that connect to the fovea are pushed away?

A

Avascular zone

72
Q

The optic nerve is a _____-free zone

A

photoreceptor

73
Q

Its intraocular portion, the optic disc is positioned approximately _____ temporal to the ____

A

15 degrees; fovea

74
Q

Why does the receptor gap does not present a conscious visual problem?

A

The binocular vision fills in the gap

75
Q

What is the portion of the electromagnetic spectrum that is visible to the human eye?

A

Visible spectrum

76
Q

Human eye wavelengths are from ____ to_____

A

400; 700nm

77
Q

Birds can see ultraviolet (____-____)

A

300-400nm

78
Q

Human have _____ vision but most mammals are _______ and they can’t see _____. some species are _____ with an extra UV opsin

A

trichromatic; dichromatic; red; tetrachromatic

79
Q

Which animal can see the most colours? and they have how many types of photoreceptor cells?

A

Mantis shrimp; 12-16

80
Q

How many times will a transmembrane protein go through the membrane?

A

7 times

81
Q

The 3 different types of cones and rods have slightly different ___ which are sensitive to different ____

A

opsins; wavelengths

82
Q

How many types of optimum protein?

A

1

83
Q

Wavelength of ___ will activate blue opsin protein

A

420

84
Q

Wavelength of ___ will activate green opsin protein

A

534

85
Q

Wavelength of ___ will activate red opsin protein

A

564

86
Q

Wavelength of ___ will activate rhodopsin

A

498

87
Q

If move away from the wavelength, can the opsins still be activated?

A

Yes, but less efficient

88
Q

People with normal vision are _____

A

Trichromat

89
Q

People who can’t see red are ____

A

Protanopia

90
Q

People who can’t see green are ____

A

Deuteranopia

91
Q

Which disease’s vision appears to be darker?

A

Protanopia

92
Q

Why red-green colourblindness is more common in male?

A

Male has one X chromosomes and red-green are on X chromosomes. If one is defected, they will be colourblind. But female has 2 X chromosomes, so it takes them to have both to be defective.

93
Q

Shining light on a photoreceptor, leads to membrane _____

A

hyperpolarisation

94
Q

What absorbs photons?

A

Rhodopsin molecules in the outer segment discs

95
Q

Absorbing photons leads to ________ and further leads to _______ and _______

A

the closure of cGMP-gated channels in the plasma membrane; hyperpolarizes the membrane; reduces the rate of release of the neurotransmitter glutamate

96
Q

Light stimulation of rhodopsin in the receptor disks leads to ________ (____), which in turn activates a ___________ (___). The ________ hydrolyzes _____, reducing its concentration in the outer segment and leading to ___________

A

activation of a G-protein; transducin; phosphodiesterase; PDE; PDE; cGMP; closure of sodium channels in the outer segment membrane

97
Q

1 rhodopsin can activate ____ G Protein. signal is hence amplified ____

A

500; 500 times

98
Q

1 activated PDE can hydrolyze ____ cGMP. signal is amplified ___

A

10^5

99
Q

Retinitis Pigmentosa is an blinding disease caused by loss of ____ at first and loss of _____ secondarily in the _____

A

rods; cones; retina

100
Q

Retinitis Pigmentosa generally affected how many people in the world?

A

1 in 4000

101
Q

Retinitis Pigmentosa can be caused by mutations in any of more than ____ genes, and a lot of these genes are in the ________ pathway

A

60; phototransduction

102
Q

Retinitis Pigmentosa patients are ____ at young age, later form _____ and slowly become _____

A

night blind; tunnel vision; completely blind

103
Q

Is Retinitis Pigmentosa treatable?

A

No

104
Q

Rhodopsin absorbs light, converted from _____ in dark (____) to ______ (____)

A

bent shape; cis-retinal; straight; trans-retinal

105
Q

_______ are faster to regenerate their _______, _________ for 50%; while it takes ______ to regenerate 50% of the bleached rhodopsin

A

Cones; photopsin; 90 secs; 5 minutes

106
Q

What are the functions of retinal pigmented epithelium?

A

Prevents light refractions throughout the eyeballs; stores large quantities of vitamin A, which is a precursor of visual pigment

107
Q

What is RPE65?

A

A retinal isomerohydrolase necessary for producing 11-cis-retinal

108
Q

Leber’s congenital amaurosis is a ______ diseases with problems in the ______.

A

congenital; visual cycle

109
Q

Leber’s congenital amaurosis is an ________ diseases in about 1 in ______ people.

A

autosomal recessive; 80000

110
Q

Leber’s congenital amaurosis condition is caused by mutation of any of ____ known genes, including _____

A

18; RPE65

111
Q

Leber’s congenital amaurosis lose vision at a ______ age

A

young

112
Q

Is Leber’s congenital amaurosis treatable?

A

Yes, by gene therapy

113
Q

More than _____ nerve fibres connect each eye to the brain

A

1 million

114
Q

Can retinas be transplanted?

A

No, because don’t know how to connect 1 nerve to 1 neuron in the brain

115
Q

Retinal ganglion cells types are based on their ____ (ON& OFF cells)

A

firing property

116
Q

Retinal ganglion cells types are based on their size. Small: _____ Big:____ and what they responsible for?

A

Midget ganglion cells (colours); Parasol ganglion cells (movement)

117
Q

Receptive field of an individual sensory neuron is the particular region of the sensory space in which a stimulus will ________

A

trigger the firing of that neuron

118
Q

The receptive field of a ganglion cell in the retina of the eye is composed of input from _________

A

all of the photoreceptors which synapse with it

119
Q

ON cells = ____-center; _____-surround cells

A

on; off

120
Q

If the light intensity is suddenly increased, _______ fire more rapidly

A

on-cells

121
Q

If the light intensity is suddenly decreased, _______ fire more rapidly

A

off-cells

122
Q

OFF cells = ____-center; _____-surround cells

A

off; on

123
Q

When the neuron is not stimulated, what will the neuron do?

A

Fire at basal rate (homeostatic)

124
Q

What happens if light stays on?

A

First is fire rapidly, then get used to the signal and fire to the basal rate (protective mechanism)

125
Q

______ emphasize of moving objects and _____ in the visual input

A

Ganglion cells; temporal changes

126
Q

A moving object elicits strong firing in the RGCs near the ______ of the object’s image because these are the only regions of ________ and where the __________

A

edges; spatial contrast; light intensity changes over time

127
Q

The __/___ & ___ of an object are important info for RGCs

A

shape; outline; movement

128
Q

What is microsaccade?

A

When fixing our gaze, small automatic eye movements scan the image across the retina to prevent the world from disappearing

129
Q

What is this effect? : When one fixates on a particular point for even a short period of time, an unchanging stimulus away from the fixation point will fade away and disappear

A

Troxler effect

130
Q

The vertical excitatory pathways are modulated by ______

A

horizontal inhibitory connections

131
Q

________ begins at the ______ segment of the ______ when a pigment molecule absorbs a photon. ______ is amplified, photoreceptor cell is ______ and the glutamate release is _______

A

Phototransduction; outer; photoreceptor cell; G protein cascade; hyperpolarized; reduced

132
Q

Fine spatial resolution is maintained only in a _____ region at the _______

A

narrow; center of gaze-fovea

133
Q

Different population of ____ transmit multiple ________ of the retinal image along ____ pathways

A

RGCs; neural representations; parallel

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