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Hugh's MD1 Neuro > Vision > Flashcards

Flashcards in Vision Deck (49):
1

Which work at night, cones or rods?

Rods

1

What is melanoma associated retinopathy?

A rare complication of melanoma

Antibodies produced against ON bipolar cells 

3

What level of vision is considered legal blindness?

6/60

4

Which work during the day, cones or rods?

Cones

4

Which muscle dilates the pupils?

Dilator papillae

5

What happens to optic nerve fibres at the optic chiasm?

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

5

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

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

6

Which neurotransmitter do ganglion cells release?

Glutamate

6

Where does the optical radiations communicate between?

Lateral geniculate nucleus of the thalamus and visual cortex

7

Most ganglion cells send afferent information to which brain area?

Lateral geniculate nucleus of the thalamus

8

What is special about intriniscally photosensitive ganglion cells ipGCs?

They don't have connection with photoreceptor cells

They have their own photoreceptor protein called melanopsin

9

Do ON bipolar cells depolarise or hyperpolarise?

Depolarise

11

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

8 minutes off centre

11

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

6

Parvocellular and Magnocellular

12

Do OFF bipolar cells hyperpolarise or depolarise?

Hyperpolarise

12

What type of damage usually results in macula sparring?

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

12

How are melanopsin cells involved in circadian rhythms?

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

14

Why is vision best at the centre?

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

14

How do ganglion cells respond to light?

They depolarise

- Increasing their firing of action potentials

15

Where is the optic chiasm located?

Above the turkish saddle of the body of the sphenoid bone

16

What do horizontal cells do?

Receive signals from photoreceptors and send inhibitory GABA responses = hyperpolarise

17

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

2,3,5

 

19

What is visual acuity?

The ability to resolve fine detail

20

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

Optic chiasm

Pathology in the pituitary gland and internal carotid

21

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

Vertical: Photoreceptor > Bipolar cells > Ganglion cells

Horizontal: Horizontal cells and Amacrine cells

22

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

M

10%

23

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

P

80%

24

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

12/6

25

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

Behind the chiasm

26

How does cGMP interact with Na channels?

cGMP keeps Na channels open causing constant depolarisation

27

How are vision fields arranged topographically on the visual cortex?

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

What is the receptor field of a ganglion?

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

31

What does 6/12 mean?

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

32

How are melanopsin ganglion cells involved in the papillary reflex?

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

33

Which ganglion cells are very large?

M

34

Are there more cones or rods?

Rods - 95:5

35

How do photoreceptors response to light?

Light causes a conformational change in a protein

Rods: rhodopsin

Cones: cone-opsins

37

What structural feature is exceptional about amacrine cells?

They have no axons

38

Explain the phototransduction pathway

Light hit the photoreceptor >

Conformational change in protein eg rhodopsin > 

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

Hyperpolarisation

39

How many types of bipolar cells do cone cells have?

9

40

What is the density of rods at the fovea?

0

42

What are the two types of bipolar cells?

ON and OFF cells

43

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

Through horizontal cells that release inhibitory GABA signal

44

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

Eye or its optic nerve

45

What signal do amacrine cells release?

Inhibitory

46

Which of the retinal cells fire action potentials?

Ganglion cells only

47

How does pupil size effect vision?

The smaller the aperture - the better vision

48

What level of vision is required to drive?

6/12

49

The right visual field is view by which hemisphere?

The left