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BAB > L07: Vision > Flashcards

L07: Vision Flashcards

1
Q

What is the order of structures that light passes through in the eye

A 
Cornea 
Iris
Lens
Retina 
Fovea
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2
Q

What is the fovea

A

Specialised part of the retina

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3
Q

What role does the fovea have in the eye

A

Focus the image in detail

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4
Q

What is the space behind the lens filled with

A

Vitreous humor

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5
Q

What is the space in form of the lends filled with

A

Aqueous humus

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6
Q

How is the lens attached to the outer edges of the eyeball

A

Via zonule fibres

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7
Q

What is the zonule fibres attached to

A

Ciliary muscle

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8
Q

What happens to the shape of the lens when the ciliary muscles contract

A

Flattens

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9
Q

Where is the aqueous humor located

A

In front of the lens

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10
Q

What is the role of the aqueous humor

A

Provide nutrients for the cells of the cornea

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11
Q

Why does the cornea need nutrients from the aqueous humor

A

It doesn’t not have a blood supply hence the reason it is transparent

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12
Q

What is the chamber behind the iris known as

A

Posterior chamber

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13
Q

What is the chamber called that is in front of the iris but behind cornea

A

Anterior chamber

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14
Q

When aqueous humor is produced which chamber does it get secreted into

A

Posterior chamber

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15
Q

How is the aqueous humor flow into the anterior chamber

A

It gets reabsorbed from the posterior chamber cells

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16
Q

Therefore overall where is aqueous humor located

A

Posterior and anterior chamber that are part fo a compartment

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17
Q

What happens when the pressure inside the compartment that contains aqueous humour increases

A

Glaucoma

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18
Q

What can happen if glaucoma is left untreated

A

Increased pressure can block the eye and cut off blood flow to the retina

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19
Q

What are the 2 causes of glaucoma

A

Angel closure

Open angle

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20
Q

What is angle closure

A

When the iris adheres to the cornea so you block the sire where aqueous humor is reabsorbed into the anterior chamber

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21
Q

What is open angle

A

Where angle of reabsorption is not blocked and it is caused by sclerosis of the veins in the angle which slows the reabsorption

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22
Q

What is the treatment of glaucoma

A

Surgery
Beta blockers
Prostaglandins blockers

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23
Q

What is the role of beta blockers for treatment

A

Reduces the production of aqueous humor

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24
Q

What is the role of prostaglandin analogues

A

Increase blood drainage by vasodilation the vessels

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25
Q

What are the cell types found in the retina

A 
Photoreceptors 
Bipolar 
Horizontal 
Amacrine 
Ganglion cells
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26
Q

Do photoreceptors or bipolar cell generate AP

A

No

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27
Q

Which cells in the retina generate AP

A

Ganglion cells

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28
Q

What is the role of horizontal and amacrine cells

A

Modulate transmission of info and enable lateral transmission for indirect pathway

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29
Q

Where does the ganglion cell axons join

A

At the optic disc to form optic nerve

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30
Q

What does the optic nerve do

A

Leave the eye and go to the brain

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31
Q

What is the main role of photo receptors

A

Detect light

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32
Q

What are the 2 types of photoreceptors

A

Rods

Cones

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33
Q

How many segments to photoreceptors have in their structure

A

Outer segment
Inner segment
Synaptic terminals

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34
Q

What does the outer segment of photoreceptors contain

A

Photopigments

35
Q

What does the inner segment of the photoreceptors contain

A

Nucleus

36
Q

What does the synaptic terminals of photoreceptors synapse with

A

Bipolar cells

37
Q

In terms of the photoreceptors structure which segment differs between rods and cones

A

Outer segment with photopigments

38
Q

How many photopigments does rods have

A

1 type of photopigments

39
Q

What is the one type of photopigments in rods known as

A

Rhodopsin

40
Q

Where are rhodopsin located

A

In the intracellular disk of outer segments

41
Q

What is the density of rhodopsin like in the outer segment of rods

A

High

42
Q

If there are high density of rhodopsin what is the sensitivity to light like

A

High sensitivity

43
Q

How many photopigment types does cones haves

A

3 types

44
Q

What are the types of photpigments in cones based on

A

Colours of light that they respond to

45
Q

What are the 3 colours of light that photopigments of cones detect

A

Red light
Green light
Blue light

46
Q

Where in the outer segment are photopigments of cones found

A

In folding surface membrane

47
Q

What is the density of photopigments in cones like

A

Low density

48
Q

If there are low density of photopigments in cones what does it mean to generate an electrical signal

A

We need a higher light level due to lower sensitivity to light

49
Q

What time of the day of photopigments in cones involved

A

Seeing colour during day time and not at night

50
Q

What is the blind sport

A

The point where the optic nerve leaved the eye at the optic disc

51
Q

Where are the the most proportion of cones located

A

The closer you get to the fovea

52
Q

Why does the peripheral retina have high sensitivity to light

A

Has lots of rods

Many Rods are connect via bipolar cells to 1 ganglion cells

53
Q

What does it mean if rods are connected via bipolar cell to 1 ganglion cells

A

It the light is low and a signal is small in the RODS because it is connected to 1 ganglion cells the sum total of signal from the rods will be enough to produce a signal

54
Q

What is the macula

A

Central part of the retina

55
Q

What is the fovea

A

Where you have cones

56
Q

What are the cones connected to in the Forvea

A

1 cone is connected to 1 ganglion cell

57
Q

What does it mean if 1 cone connects to 1 ganglion cell

A

There is high detail because 1 ganglion is relieve info from 1 cone

58
Q

What time of the day is the activity of rods more

A

In the dark

59
Q

What is the activity in the dark for rods like

A

1) rhodopsin is inactive in the dark because there is no light
2) on the rod cell membrane there are cyclic GMP- gated cation channels
3) in the dark when there is a lot of cyclic GMP, it binds to cyclic GMP gates cation channels that open
4) this causes sodium influx when the cyclic GMP gated cation channel open
5) sodium influx causes depolarisation = dark current
6) membrane potential becomes -30mv
7) at -30mv the photoreceptors that have the synaptic terminal connecting with bipolar cells causes the release of glutamate at the synapse
8) bipolar cells receive a synaptic signal in the absence of a signal in the dark

60
Q

What happens to the rods when there is light

A

1) retinal (component of rhodopsin) absorbs light and undergoes changes in structure
2) this activates the opsin (GCPRs -component of rhodopsin)
3) opsin acitvates G protein when GTP binds to it
4) G protein acitvates PDE
5) PDE breaks cyclic CGMP
6) breakage of cyclic CGMP causes a closure of cyclic CGMP channels
7) this stops sodium influx
8) resting hyperpolarisation
9) hyperpolaristion causes a decrease in release of glutamate at the synapse with bipolar cells

61
Q

What are the 2 pathway a signal is sent form the photoreceptors to the ganglion cell

A

Direct pathway

Indirect pathway

62
Q

What cells the direct pathway involve

A

Photoreceptors
Bipolar cells
Ganglions cells

63
Q

What happens to the photoreceptors in the direct pathway in light

A

Hyperpolarise (rods and cones)

64
Q

What does electrical response that you get depend on

A

On bipolar cells and ganglion cells

Off bipolar cells and ganglion cells

65
Q

What happens to on bipolar and ganglion cells in repsonse to light

A

Depolarise

66
Q

What happens to the off bipolar cells and ganglion cells in repsonse to light

A

Hyperpolarise

67
Q

For on bipolar cells and ganglion cells what happens to the glutamate released by photoreceptors in the light

A

Decrease to cause depolarisation in on cells

68
Q

What happens to the glutamate from photoreceptors to off bipolar and ganglions cells in the light

A

Glutamate decreases to cause hyperpolarization

69
Q

Why do we get a decrease of glutamate from photoreceptors in light

A

Remember opsin and retinal are activated that causes PDE to break cyclic GMP so sodium influx decreases and hyperpolarization occurs to cause decrease in glumate in light

70
Q

What causes glutamate to cause depolarisation of hyperpolarization in on/off cells

A

Differnt glumate receptors on off/on cells

71
Q

What are the 2 parts of receptive filed

A

Central part

Surround part

72
Q

What cell connections does the central part involve

A

Direct connection with photoreceptors

73
Q

What connection does the surround part involve

A

Indirect connections with horizontal or amacrine cells

74
Q

What pathway is the central part involved in

A

Direct pathway

75
Q

What pathway is the surround part involved in

A

Indirect pathway

76
Q

When light hits the surround part how does signals reach the bipolar or ganglion cells

A

Via the indirect pathway that involves horizontal or amacrine cells

77
Q

What is the impact of the indirect pathway

A

To produce the opposite electrical response in bipolar and ganglion cells

78
Q

In the indirect pathway if the bipolar cells is on what is the overall response

A

Hyperpolarization of on bipolar cells becuase the indirect pathway causes the opposite response

79
Q

Which part of the receptive filed dominates

A

The central part i.e the direct pathway

80
Q

Where does the optic nerve join at to becomes the optic tract

A

Optic chiasm

81
Q

What side of the hemifield does the right optic tract take info from

A

Left hemifield

82
Q

What side of the hemifield does the left optic tract take the infor from

A

Right hemifield

83
Q

If there is a transaction fo the left optic tract what side of the hemifield is lost completely

A

Right hemifield

84
Q

If there is a transection of the optic chiasm which side of the hemifield is lost completely

A

Left and right sides of hemifield

BAB (21 decks)

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