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Foundations of Neuroscience > Vision > Flashcards

Vision Flashcards

1
Q

Where is the vitreous humour?

A

Behind the lens

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2
Q

What is the vitreous humour?

A

Jelly like substance

Necessary for structural stability

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3
Q

Where is aqueous humour?

A

Behind the cornea

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4
Q

What does the aqueous humour do?

A

Deliver nutrients to the cornea

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5
Q

Where is aqueous humour made?

A

Posterior chamber (behind the iris)

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6
Q

Where is aqueous humour reabsorbed?

A

Anterior chamber

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7
Q

Where does refraction occur?

A

Cornea

Lens

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8
Q

What is accommodation?

A

Adjusting the thickness of the lens

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9
Q

What controls the thickness of the lens?

A

The ciliary muscles

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10
Q

What connects the lens to the ciliary muscle?

A

Zonule fibres

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11
Q

How does the lens thicken?

A

Ciliary muscle constricts
Zonule fibres relax
Lens has natural elasticity

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12
Q

When does the lens thicken or thin?

A

Near objects = thin

Far objects = thicken

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13
Q

How does the lens thin?

A

Ciliary muscle relaxes
Zonule fibres tense
Lens thinned

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14
Q

What nervous system controls the muscles of the eye?

A

The autonomic nervous system

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15
Q

Besides the ciliary muscle, where else are there muscles in the eye?

A

Around the pupil

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16
Q

Name the two types of photoreceptor

A

Rods

Cones

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17
Q

What connects the cells of the retina?

A

Chemical synapses

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18
Q

What generates action potentials in the eye?

A

Ganglion cells

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19
Q

What allows lateral transmission?

A

Horizontal cells

Amacrine cells

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20
Q

Name the three structural parts of photoreceptors

A

Outer segment
Inner segment
Synaptic terminals

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21
Q

Where are photopigments located?

A

Outer segment

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22
Q

What is the name of the photopigment in rods?

A

Rhodopsin

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23
Q

What are photopigments specific to?

A

Wavelength of light

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24
Q

Where is rhodopsin found?

A

Intracellular disks

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25
Q

How sensitive are rods? Why?

A

Very
High density of intracellular disks
High levels of rhodopsin
High surface area

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26
Q

How many photopigments are there in cones?

A

3

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27
Q

What are the three photopigments in cones?

A

Red opsin
Blue opsin
Green opsin

28
Q

Where are the opsins found?

A

Infoldings of surface membrane

29
Q

How sensitive are cones? Why?

A

Not very
Low surface area
Low levels of opsins

30
Q

Which photoreceptor is responsible for colour vision?

A

Cones

31
Q

What is the blind spot?

A

Where neurones enter the fovea and there are no photoreceptors

32
Q

Explain the distribution of cones and rods across the retina

A 
Fovea = all cones
Periphery = majority rods
33
Q

Is the periphery sensitive?

A

Very
High number of rods
Rods are very sensitive
A lot of convergence of rods to ganglion cells

34
Q

What is low visual acuity? Why is there low visual acuity at the periphery?

A

Low clarity of vision

Convergence of rods means detail is lost

35
Q

What is the macula?

A

The centre of the retina

36
Q

How sensitive is the fovea?

A

Not very
Low sensitivity of cones
1 cone: 1 gangion cell

37
Q

What happens to other cells in the fovea?

A

Lateral displacement

Allows as much light as possible to reach photoreceptors

38
Q

What is high acuity? Why is there high acuity at the fovea?

A

High clarity of vision
1 cone: 1 ganglion
Many separate signals
Detail not lost

39
Q

What is rhodopsin made up of?

A

Retinal (chromophore)

Opsin (G protein coupled receptor)

40
Q

In the dark, what is happening in a rod cell?

A

Rhodopsin is inactive
cyclicGMP-gated cation channels are open
Na+ enters the rod cell

41
Q

What is the flow of Na+ called?

A

The dark current

42
Q

What is the resting membrane potential of a rod cell in the dark?

A

-30mV

43
Q

Is the cell depolarised in the dark?

A

Yes

44
Q

What happens at the synapse in the dark?

A

Glutamate is released

45
Q

When light hits a rod cell, what absorbs the light?

A

Retinal

46
Q

What conformation change happens to retinal?

A

Changes from 11-cis to all-trans

47
Q

What does the change in retinal trigger?

A

Opsin is activated

48
Q

What happens once optin is activated?

A

GTP binds to the G-protein

49
Q

What does the G-protein activate?

A

Phosphodiesterase

50
Q

What does phosphodiesterase do?

A

Breaks down cyclicGMP

Channel closes

51
Q

Why does the cell hyperpolarise?

A

The Na+ channels close

Leak channels for K+ remain open

52
Q

What happens at the synapse in the light?

A

Glutamate release stops

53
Q

What is the route of transmission through the retina?

A

Photoreceptor
Bipolar cell
Ganglion cell

54
Q

What do photoreceptors do in the light?

A

Hyperpolarise

55
Q

What are the two classifications of bipolar cells?

A

On

Off

56
Q

What do on bipolar cells do in the light and in the dark?

A

Depolarised by light
In the dark the glutamate from the photoreceptor hyperpolarises them
In the light the lack of glutamate depolarises them

57
Q

What do off bipolar cells do in the light and in the dark?

A

Hyperpolarised by light
In the dark, glutamate depolarises them
In the light, lack of glutamate hyperpolarises them

58
Q

What causes opposite actions of bipolar cells?

A

The receptors they possess

59
Q

Name the two classes of ganglion cell

A

On and off

60
Q

For both ganglion cells and bipolar cells. Summarise on and off

A 
On = depolarised by light
Off = hyperpolarised by light
61
Q

What is the receptive field?

A

The region of the retina that influences a bipolar or ganglion cell

62
Q

What are the two divisions of the receptive field?

A

Central part

Surround part

63
Q

What is in the central part?

A

Direct connections from photoreceptors

64
Q

What is the surround part?

A

Lateral transmission of information via either horizontal or amacrine cells

65
Q

What happens when light is present in the surround field?

A

The opposite electrical response in bipolar and ganglion cells

66
Q

Why is the input of the surround field necessary?

A

Helps create contrast in image

Foundations of Neuroscience (15 decks)

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