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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
What are the cell types found in the retina
``` Photoreceptors Bipolar Horizontal Amacrine Ganglion cells ```
26
Do photoreceptors or bipolar cell generate AP
No
27
Which cells in the retina generate AP
Ganglion cells
28
What is the role of horizontal and amacrine cells
Modulate transmission of info and enable lateral transmission for indirect pathway
29
Where does the ganglion cell axons join
At the optic disc to form optic nerve
30
What does the optic nerve do
Leave the eye and go to the brain
31
What is the main role of photo receptors
Detect light
32
What are the 2 types of photoreceptors
Rods | Cones
33
How many segments to photoreceptors have in their structure
Outer segment Inner segment Synaptic terminals
34
What does the outer segment of photoreceptors contain
Photopigments
35
What does the inner segment of the photoreceptors contain
Nucleus
36
What does the synaptic terminals of photoreceptors synapse with
Bipolar cells
37
In terms of the photoreceptors structure which segment differs between rods and cones
Outer segment with photopigments
38
How many photopigments does rods have
1 type of photopigments
39
What is the one type of photopigments in rods known as
Rhodopsin
40
Where are rhodopsin located
In the intracellular disk of outer segments
41
What is the density of rhodopsin like in the outer segment of rods
High
42
If there are high density of rhodopsin what is the sensitivity to light like
High sensitivity
43
How many photopigment types does cones haves
3 types
44
What are the types of photpigments in cones based on
Colours of light that they respond to
45
What are the 3 colours of light that photopigments of cones detect
Red light Green light Blue light
46
Where in the outer segment are photopigments of cones found
In folding surface membrane
47
What is the density of photopigments in cones like
Low density
48
If there are low density of photopigments in cones what does it mean to generate an electrical signal
We need a higher light level due to lower sensitivity to light
49
What time of the day of photopigments in cones involved
Seeing colour during day time and not at night
50
What is the blind sport
The point where the optic nerve leaved the eye at the optic disc
51
Where are the the most proportion of cones located
The closer you get to the fovea
52
Why does the peripheral retina have high sensitivity to light
Has lots of rods | Many Rods are connect via bipolar cells to 1 ganglion cells
53
What does it mean if rods are connected via bipolar cell to 1 ganglion cells
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
What is the macula
Central part of the retina
55
What is the fovea
Where you have cones
56
What are the cones connected to in the Forvea
1 cone is connected to 1 ganglion cell
57
What does it mean if 1 cone connects to 1 ganglion cell
There is high detail because 1 ganglion is relieve info from 1 cone
58
What time of the day is the activity of rods more
In the dark
59
What is the activity in the dark for rods like
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
What happens to the rods when there is light
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
What are the 2 pathway a signal is sent form the photoreceptors to the ganglion cell
Direct pathway | Indirect pathway
62
What cells the direct pathway involve
Photoreceptors Bipolar cells Ganglions cells
63
What happens to the photoreceptors in the direct pathway in light
Hyperpolarise (rods and cones)
64
What does electrical response that you get depend on
On bipolar cells and ganglion cells | Off bipolar cells and ganglion cells
65
What happens to on bipolar and ganglion cells in repsonse to light
Depolarise
66
What happens to the off bipolar cells and ganglion cells in repsonse to light
Hyperpolarise
67
For on bipolar cells and ganglion cells what happens to the glutamate released by photoreceptors in the light
Decrease to cause depolarisation in on cells
68
What happens to the glutamate from photoreceptors to off bipolar and ganglions cells in the light
Glutamate decreases to cause hyperpolarization
69
Why do we get a decrease of glutamate from photoreceptors in light
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
What causes glutamate to cause depolarisation of hyperpolarization in on/off cells
Differnt glumate receptors on off/on cells
71
What are the 2 parts of receptive filed
Central part | Surround part
72
What cell connections does the central part involve
Direct connection with photoreceptors
73
What connection does the surround part involve
Indirect connections with horizontal or amacrine cells
74
What pathway is the central part involved in
Direct pathway
75
What pathway is the surround part involved in
Indirect pathway
76
When light hits the surround part how does signals reach the bipolar or ganglion cells
Via the indirect pathway that involves horizontal or amacrine cells
77
What is the impact of the indirect pathway
To produce the opposite electrical response in bipolar and ganglion cells
78
In the indirect pathway if the bipolar cells is on what is the overall response
Hyperpolarization of on bipolar cells becuase the indirect pathway causes the opposite response
79
Which part of the receptive filed dominates
The central part i.e the direct pathway
80
Where does the optic nerve join at to becomes the optic tract
Optic chiasm
81
What side of the hemifield does the right optic tract take info from
Left hemifield
82
What side of the hemifield does the left optic tract take the infor from
Right hemifield
83
If there is a transaction fo the left optic tract what side of the hemifield is lost completely
Right hemifield
84
If there is a transection of the optic chiasm which side of the hemifield is lost completely
Left and right sides of hemifield

BAB (21 decks)

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