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NSB > 17. Retinal Function and Visual Perception > Flashcards

17. Retinal Function and Visual Perception Flashcards

1
Q

What range of electromagnetic wave length is visible to the eye?

A

400-750 nm

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2
Q

What does length of an electromagnetic wave correspond to?

A

Colour

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3
Q

What does amplitude of an electromagnetic wave correspond to?

A

Brightness

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4
Q

What effect does a closer light source have on the focal distance?

A

Longer focal distance

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5
Q

What is accommodation?

A

Lens alters focal length

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6
Q

What are the functions of the pupil?

A

Control light entering eye

Depth of focus

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7
Q

How does the pupil control depth of focus?

A

Constriction cuts out peripheral light

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8
Q

What is the effect of sympathetics on the pupil?

A

Contract radial muscle of iris

Cause dilation

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9
Q

What is the effect of parasympathetics on the pupil?

A

Contract circular muscle of iris

Cause constriction

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10
Q

What is used to test for visual acuity?

A

Snellen chart

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11
Q

What is visual acuity?

A

Ability to distinguish between 2 nearby points

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12
Q

What does each part of 20/20 stand for?

A

First 20 is distance in feet from Snellen chart

Second is size of the smallest letter read

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13
Q

What are the 3 cell types in the retina?

A

Photoreceptors
Bipolar
Ganglion

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14
Q

What do rods detect?

A

Light intensity

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15
Q

Why is visual acuity low in rods?

A

Many rods converge to the same ganglion

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16
Q

What do cones detect?

A

Colour

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17
Q

What is the equation for photon energy?

A

hv (planck constant x frequency)

hc/ λ (planck constant x speed of light/ wavelength)

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18
Q

Which cells are non-image forming photoreceptors?

A

Retinal Ganglion Cells

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19
Q

What do Retinal Ganglion cells control?

A

Circadian rhythm

20
Q

What light-sensitive pigement is used by retinal ganglion cells?

A

Melanopsin

21
Q

What is the name for loss of photoreceptor cells?

A

Macular degeneration

22
Q

What is found in the outer segment of cones?

A

Discs: specialised receptor region

23
Q

What is found in the inner segment of cones?

A

Mitochondria and other organelles

24
Q

What is phototransduction?

A

Converting light to an electrical signal

25
Q

What pigment is used in rods?

A

Rhodopsin

26
Q

What is rhodopsin composed of?

A

Retinal and opsin

27
Q

What neurotransmitter is released by rods?

A

Glutamate

28
Q

What is meant by the dark current?

A

Na+ enters causing depolarisation

K+ leaves causing repolarisation

29
Q

What happens once light hits rhodopsin?

A

11-cis retinal converted to 11-trans retinal

30
Q

What does 11-trans retinal activate?

A

Transducin

31
Q

What does transducin activate?

A

Phosphodiesterase

32
Q

What is the function of phosphodiesterase?

A

Cleave cGMP to GMP

Low cGMP closes Na+ channels: hyperpolarisation

33
Q

What are the 3 types of cones?

A

Blue (short)
Green (medium)
Red (long)

34
Q

What are the percentage population of each type of cone?

A

Short: 16%
Medium: 10&
Long: 74%

35
Q

What is colour blindness?

A 
Inherited absence of one or more class of colour pigment
L and M cones are x-linked
36
Q

What is it called when someone lacks red cones?

A

Protanope

37
Q

What is it called when someone lacks green cones?

A

Deuteranope

38
Q

What is it called when someone lacks blue cones?

A

Tritanope

39
Q

How do photoreceptors adapt to the dark?

A

Light is insufficient to activate cones

Wait for regeneration of rod rhodopsin (20-30 mins)

40
Q

What is night vision called?

A

Scotopic vision

41
Q

How do photoreceptors adapt to strong light?

A

Pigment in rods bleaches

Brain switches to cone-only info processing

42
Q

Which fibres of the optic nerve decussate?

A

Nasal

Temporal don’t

43
Q

Where in the eyes is the left visual field taken in from?

A

Right side of each eye

44
Q

Where is visually detected movement processed?

A

Parietal lobe

45
Q

Where is perception of shape and colour processed?

A

Temporal lobe

NSB (22 decks)

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