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Module 202 Neuroscience & behaviour > T2 L10 Physiology of vision > Flashcards

T2 L10 Physiology of vision Flashcards

1
Q

How is focus varied?

A

Changing shape & power of the lens

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2
Q

What does the ray bending?

A

Cornea does 2/3

Lens does other 1/3 & allows focus to vary (accommodation)

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3
Q

What is hypermetropia?

A

Long sightedness

Eyeball is too short or lens system too weak

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4
Q

How is hypermetropia corrected?

A

Converging lens

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5
Q

What is myopia?

A

Short sightedness

Eyeball is too long or lens system too strong

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6
Q

How is myopia corrected?

A

Add diverging lens

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7
Q

What is the refractive power of a lens measured in?

A

Dioptres
Reciprocal of focal length in metres
2D spectacle has focal length of 0.5m

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8
Q

What is the consequence of vertebrate retina evolving back to front?

A

Ganglion cells & blood vessels are in light path to photoreceptors except in fovea

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9
Q

What are the 3 direct processing layers?

A

Receptors
Bipolar cells
Ganglion cells

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10
Q

What are the 2 transverse processing layers?

A

Horizontal cells

Amacrine cells

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11
Q

What happens when a proton hits rhodopsin molecule?

A

Retinal flips from 11 cis to all trans

Leads to biochemical events resulting from the electrical change (hyper polarisation) in the cell membrane

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12
Q

What do ganglion cells respond strongly & weakly to?

A

Weakly to changes in overall light intensity

Strongly to local contrast i.e. light on a dark background or dark on a light background

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13
Q

What is the basic response pattern?

A

Either on centre or off centre
On cells are stimulated by stimulus in centre & inhibited by stimulus in surrounding
Off cells are inhibited by stimulus in centre & stimulated by stimulus in surrounding

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14
Q

What is the sensitivity of red cones?

A

560nm

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15
Q

What is the sensitivity of green cones?

A

530nm

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16
Q

What is the sensitivity of blue cones?

A

420nm

17
Q

What is the sensitivity of rods?

A

500nm

18
Q

What is the most frequent type of cone?

A

Red cone then green cone then blue cone

19
Q

What is the spacing between cones?

A

2.5 micrometers which corresponds to angle of 0.5 minutes of arc

20
Q

What is colour blindness?

A

Loss or modification of one of the 3 pigments

21
Q

What genes are on the X chromosome?

A

Genes for red & green pigment

22
Q

What chromosome is the gene for blue pigment?

A

Chromosome 7

23
Q

What is central achromatopsia?

A

Rarer kind of colour blindness

Caused by damage to cortical colour processing areas (V4)

24
Q

Where do optic tracts relay?

A

In lateral geniculate nucleus of thalamus

A part goes to superior colliculus in midbrain

25
Q

Where does the output of the lateral geniculate nucleus go to?

A

Striate cortex in occipital lobe (V1)

26
Q

Describe columnar organisation in primary visual cortex

A

Outer dominance column
Smaller orientational columns
Colour blobs

27
Q

Describe smaller orientational columns

A

Orientation of optimal stimuli various systemically across surface

28
Q

Describe colour blobs

A

Colour information kept separate from orientation

Passed on to other regions e.g. V4

29
Q

What are some causes of partial visual loss?

A

Left eye blindness
Homonymous hemianopia
Bitemporal hemianopia
Scotoma

30
Q

What are the causes of scotoma?

A

Retinal damage
Lesions in visual cortex
Pressure from tumours restricting optic nerve, chasm, optic tract or optic radiation

31
Q

Where does the dorsal stream go and what is it for?

A

From occipital to parietal cortex
Location
Motion
Action

32
Q

Where does ventral stream go and what is it for?

A

From occipital to temporal cortex
Object & face identity
Conscious perception

33
Q

What is visual agnosia?

A

Person can see but can’t recognise or interpret visual information due to disorder in parietal lobes

34
Q

What is visual ataxia?

A

Person can’t describe but can’t act

35
Q

What is prosopagnosia?

A

Inability to recognise familial faces

Associated with damage to specific parts of temporal lobe such as fusiform gyrus on underside of lobe

36
Q

What causes blindsight?

A

Destruction of striate cortex leading to blindness in part o visual field corresponding to damaged area
Individuals not aware of stimuli within blind field but if forced to guess they can perform some discrimination tasks & point accurately to locations of stimuli (blindsight phenomena)

37
Q

What is the vestibulo-occular reflex?

A

Stabilises gaze by countering movement of head

38
Q

What is optokinetic reflex?

A

Stabilises image of moving object on retina

39
Q

What is pupillary reflex?

A

If one eyes is illuminated, both will contract as both pretectal & Edinger Westphal nuclei receive signals from both eyes

Module 202 Neuroscience & behaviour (39 decks)

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