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Disease, diagnostics and therapeutics > Vision > Flashcards

Vision Flashcards

1
Q

the eye is design to

A

focus light on specialised nerve endings that translate light wave and photons into pictures our brink an understand

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2
Q

light which reaches photoreceptors of the retina

A

and sends signals via the visual pathways tot he usual cortex in the occipital lobes

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3
Q

human visible light wave lengths

A

400>550nm

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4
Q

what makes up the ouster fibrous layer of the eye

A

cornea, conjunctiva and sclera

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5
Q

middle vascular layer

A

iris, ciliary body and chorois

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6
Q

inner neural layer

A

retain and single layer of retinal pigmented epithelium

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7
Q

the lens

A

focuses light waves onto the retina and specifically the fovea

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8
Q

iris

A

is a circular structure with a central opening - the pupil

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9
Q

what divides the internal space into an anterior chamber in the front of the iris and a posterior chamber between the iris and the lens

A

iris

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10
Q

posterior and anterior chambers

A

contain aqueous humour secreted by ciliary body

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11
Q

vitreous humour

A

fills the main cavity of the eye behind the lens and helps maintain the shape of the eye

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12
Q

central retinal artery

A

provides nutrients and oxygen for the retina

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13
Q

central retinal vein

A

take away oxygen poor blood to be oxygenated

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14
Q

tetina

A

light sensitive part f the ye containing photoreceptors

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15
Q

fovea

A

is the most light sensitive part of the eye- most colour snesiitve

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16
Q

optic nerve

A

where photoreceptors of the retina send signal via the visual pathways to the visual cortex i the occipital lobe

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17
Q

optic nerve is famous as being

A

a blind spot- no photoreceptors

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18
Q

the retina contains

A

the neuronal tissue of the eye

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19
Q

5 types of neurones in the retina

A

rods, cones, amacrine, horizontal, bipolar cells

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20
Q

the fovea only contains

A

cones- an area which provides high visual acuity

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21
Q

rods are

A 
Monochromatic vision
Low intensity light
Single photon
Equally distributed throughout the retina
rhodopsin as visual pigment
22
Q

cones

A 
Colour vision
High light threshold
Higher acuity
Hundreds of photons
Clustered in the macula lutea 
Within the macula lutea is a clustered pit called the fovea, which only contains cones
Highest visual acuity is found here
23
Q

photoreceptors are locate

A

at the back of the retina

24
Q

order of neurones in the retina

A

photoreceptor synapses with bipolar cell with synapses with ganglion cell

25
Q

ganglion cells and bipolar cells are neurones where

A

signals from rods and cones are integrated

26
Q

rhodopsin

A

rods

27
Q

iodopsin

A

cones

- colour blindness results from defects in cone opsins

28
Q

phototransduction occurs via which G protein

A

Gt

29
Q

what does absorption of light do to colour pigments

A

isomerise them

-starting a cascade of chemical reactant

30
Q

photo transduction in rods

A

1) in the dark Sodium (ad calcium) ion influx though cGMP- controlled cation channels which depolarised the rod cells to about -40mV
2) when photon is absorbed by 11-cis retinal it is isomers to all trans retinal (photoisomerisation)
3) rhodopsin is activates and bind to a GTP-bound protein called transducin
4) The GTP-bound alpha submit of transducer dissociates and activates a phosphodiesterase with hydrolyses cGMP- 5’-CMP
5) this closes the cation channels causes hyperpolarisation

31
Q

when photoreceptors aren’t stimulated by light

A

depolarisation

- open cGMP channels

32
Q

when photoreceptors are stimulated by light

A

hyperpolarisation

-cGMP channels closed

33
Q

Bipolar cells connect photoreceptors to

A

ganglionic cells

34
Q

ganglionic cells

A

nerves leave the eye at the optic disk dn become the optic nerve

35
Q

horizontal cells

A

revive input from multiple photoreceptor cells

- regulated activity of photoreceptor cells and makes adjustments to signals sent to bipolar cells

36
Q

amacrine cells

A

receive signals form bipolar cells

-regulate and integrate bipolar and ganglionic cells

37
Q

which is the transmitter of the visual pathway

A

glutamate- the main excitatory nt in the brain

38
Q

phototransduction pathway

A

1) light travels through layers of transparent neurones- ganglion, amacrine, bipolar and horizontal
2) and is absorbed by the rods and cones a the back of the retina
30 visual information process through several layers of neurones
4) and finally converges on ganglion cells,which send their axons to the brain

39
Q

smaller receptive fields

A

e. g. 1 ganglion per photoreceptor

- lots of detail

40
Q

large receptive filed

A

e. g. 3 cones synapse with 1 ganglion
- summarises info from 3 cones
- less detail

41
Q

when photoreceptors are not stimulated by light

A

constant state of depolarisation

-constnat release of Glu

42
Q

when the centre of the cone is stimulated by light

A

the photoreceptor becomes activates

-stimulation result in hyper polarisation due to national channels being close– > less glutamate produced

43
Q

on centre cells

A

Glu is inhibitory

1) decrease in Glu release from cone due to hyper polarisation caused by light stimulation
2) due to less Glu inhibition, there is increased depolarisation of the bipolar cells
3) therefore the bipolar cells will release more Glu
4) glu is always excitatory for ganglionic cells
5) therefore INCREASE IN FIRING RATE

44
Q

off centre cells

A

Glu is excitatory

1) less Glu due to hyper polarisation of cone
2) therefore bipolar cell become hyper polarised
3) decrease in Glu release form bipolar cells
4) decreased firing rate of off-metre ganglionic cells

45
Q

direct pathway in darkness- on centre

A

Increase in glutamate is inhibitory
Therefore increase in MetabotropicGluReceptor
Therefore hyperpolarisation
Decrease in Glu release
Therefore ganglionic cell synapsing with it are less likely to reach threshold
Action potential is less likely.

46
Q

direct pathway in darkness - off centre

A

Excited by Glu
Therefore becomes more depolarized
Ganglion which synapses with cell is more likely to reach threshold
Increase in likelyhood of AP

47
Q

APs are less likely in

A

positive centre

48
Q

APs are more likely in

A

negative centre- tells us it is dark

49
Q

Direct pathway light- On-centre

A

Decrease in glutamate is excitatory
Therefore decrease in MetabotropicGluReceptor
Therefore more depolarization
Increase in Glu release
Therefore ganglionic cell synapsing with it are more likely to reach threshold
Action potential is more likely.

50
Q

Direct pathway light- Off-centre

A

Inhibited by decreased Glu
Therefore becomes more hyperpolarized and releases less Glu
Ganglion which synapses with cell is less likely to reach threshold
decrease in likelihood of AP

51
Q

indirect pathway no light

A

horizontal and amacrine cells release GABA- inhibitory- contributing to telling us it is dark

52
Q

indirect with light

A

Horizontal and amacrine cells release less GABA

Disease, diagnostics and therapeutics (53 decks)

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