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Hugh's MD1 Neuro > Vision > Flashcards

Vision Flashcards

1
Q

Which work at night, cones or rods?

A

Rods

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1
Q

What is melanoma associated retinopathy?

A

A rare complication of melanoma

Antibodies produced against ON bipolar cells

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3
Q

What level of vision is considered legal blindness?

A

6/60

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4
Q

Which work during the day, cones or rods?

A

Cones

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4
Q

Which muscle dilates the pupils?

A

Dilator papillae

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5
Q

What happens to optic nerve fibres at the optic chiasm?

A

Fibres on the nasal aspect of the retina (that receive light from the temporal visual field) cross and head to the contralateral side of the occipital lobe

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5
Q

How are melanopsin cells involved in light sensitivity found in migraines?

A

They project to the posterior thalamic nucleus which is also where pain signals from the meninges (thought to be cause of migraines) are received

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6
Q

Which neurotransmitter do ganglion cells release?

A

Glutamate

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6
Q

Where does the optical radiations communicate between?

A

Lateral geniculate nucleus of the thalamus and visual cortex

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7
Q

Most ganglion cells send afferent information to which brain area?

A

Lateral geniculate nucleus of the thalamus

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8
Q

What is special about intriniscally photosensitive ganglion cells ipGCs?

A

They don’t have connection with photoreceptor cells

They have their own photoreceptor protein called melanopsin

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9
Q

Do ON bipolar cells depolarise or hyperpolarise?

A

Depolarise

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11
Q

At night or in low light, where is vision best?

A

8 minutes off centre

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11
Q

How many layers does the lateral geniculate nucleus of the thalamus have? What are they called?

A

6

Parvocellular and Magnocellular

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12
Q

Do OFF bipolar cells hyperpolarise or depolarise?

A

Hyperpolarise

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12
Q

What type of damage usually results in macula sparring?

A

Vascular - the cortical area for the macula in most posterior of occipital lobe where there is extra arterial supply

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12
Q

How are melanopsin cells involved in circadian rhythms?

A

They sense light and project to the suprachiasmatic nucleus which an important driver for circadian rhythms

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14
Q

Why is vision best at the centre?

A

That is where the fovea is and has the highest density of cones

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14
Q

How do ganglion cells respond to light?

A

They depolarise

  • Increasing their firing of action potentials
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15
Q

Where is the optic chiasm located?

A

Above the turkish saddle of the body of the sphenoid bone

16
Q

What do horizontal cells do?

A

Receive signals from photoreceptors and send inhibitory GABA responses = hyperpolarise

17
Q

Which layers of the lateral geniculate nucleus do the right eye input onto?

A

2,3,5

19
Q

What is visual acuity?

A

The ability to resolve fine detail

20
Q

Bitemporal vision loss is due to damage where? What is common causes?

A

Optic chiasm

Pathology in the pituitary gland and internal carotid

21
Q

What cells are in the vertical pathway of neuronal transmission and which cells interact horizontally?

A

Vertical: Photoreceptor > Bipolar cells > Ganglion cells

Horizontal: Horizontal cells and Amacrine cells

22
Q

Which ganglion cells do motion? And what percentage of the total number do they make up?

A

M

10%

23
Q

Which ganglion cells do colour and acuity and what percentage of the total number do they make up?

A

P

80%

24
Q

Which is better than average vision 6/12 or 12/6

A

12/6

25
Q

If vision is affected on the same side in both fields, where is the lesion?

A

Behind the chiasm

26
Q

How does cGMP interact with Na channels?

A

cGMP keeps Na channels open causing constant depolarisation

27
Q

How are vision fields arranged topographically on the visual cortex?

A

Centre of field on the outer region of the cortex

More lateral aspects of the field inputs to the inner aspect of the cortexs

29
Q

What is the receptor field of a ganglion?

A

The area that when light is incident on will change it’s membrane potential

31
Q

What does 6/12 mean?

A

A person with that vision must be 6m away from something a person with normal vision can see 12m away

32
Q

How are melanopsin ganglion cells involved in the papillary reflex?

A

They receive the light > relay the signal to the pretectal nucleus > which sends efferent to the Edinger Westphal > dilation of pupils

33
Q

Which ganglion cells are very large?

A

M

34
Q

Are there more cones or rods?

A

Rods - 95:5

35
Q

How do photoreceptors response to light?

A

Light causes a conformational change in a protein

Rods: rhodopsin

Cones: cone-opsins

37
Q

What structural feature is exceptional about amacrine cells?

A

They have no axons

38
Q

Explain the phototransduction pathway

A

Light hit the photoreceptor >

Conformational change in protein eg rhodopsin >

Initiation of cascade Rh > transducin > phosphodiesterase > cGMP broken down > Na channels close >

Hyperpolarisation

39
Q

How many types of bipolar cells do cone cells have?

A

9

40
Q

What is the density of rods at the fovea?

A

0

42
Q

What are the two types of bipolar cells?

A

ON and OFF cells

43
Q

How are signals from surrounding photoreceptors integrated into the central response?

A

Through horizontal cells that release inhibitory GABA signal

44
Q

If vision is affected in one eye only, where is the lesion?

A

Eye or its optic nerve

45
Q

What signal do amacrine cells release?

A

Inhibitory

46
Q

Which of the retinal cells fire action potentials?

A

Ganglion cells only

47
Q

How does pupil size effect vision?

A

The smaller the aperture - the better vision

48
Q

What level of vision is required to drive?

A

6/12

49
Q

The right visual field is view by which hemisphere?

A

The left

Hugh's MD1 Neuro (41 decks)

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