The Senses - Vision 1 (round 1)

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42 Terms

1
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Where is the biological response from photoreceptors communicated to?

intermediate relay cells

2
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Where is the info from intermediate relay cells sent?

retinal ganglion cells

3
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What is the outermost layer of the eye?

sclera

4
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What is the intermediate layer of the eye?

choroid

5
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What is the ciliary body composed of?

muscles, ligaments, processes in a ring

6
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What is the innermost layer of the eye and what does it contain?

retina, photoreceptors

7
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What fluid fills the posterior chamber behind the lens?

vitreous humor (jelly-like)

8
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What fluid fills the anterior chamber in front of the lens?

aqueous humor (watery)

9
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Name the roles of the accessory structures of the eye

refraction, accommodation, light entry regulation, spherical aberration reduction

10
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When does refraction occur?

when the light rays meet a change in medium density

11
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Where is the most major site of refraction in the eye?

interface between air and cornea

12
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What causes common refractive errors?

when the amount of refraction from accessory structures do not match the eyeball length

13
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What causes myopia?

light rays brought into focus before they hit the retina (too much refraction)

14
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What is another name for ‘normal eye’?

emmetropic

15
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What causes hypermetropia?

light rays not in focus when they hit the retina (not enough refraction)

16
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What causes astigmatism?

corneal irregularities (horizontal & vertical light rays focus on different parts of the retina)

17
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What is accommodation?

the process of the lens adjusting its curvature to gain refractive power through contraction of ciliary muscles

18
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Why does the iris regulate light entry?

prevent photoreceptors saturation, allow maximum light capture in dim light, reduce spherical aberration

19
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What is spherical aberration?

outer parts of lens distorting image due to too much refraction

20
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What are the components of the near response?

accommodation, pupils constrict, eyes converge

21
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Why is there a blind spot?

nerve fibres leaving the eye (no photoreceptors)

22
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How many types of rods and cones are there?

1 rod, 3 cones

23
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Where are the light absorbing molecules located?

outer segment of receptors

24
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Where is the transmitter located in the photoreceptors?

end of inner segment

25
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What are the two components of the visual pigment?

chromophore 11-cis-retinal, protein opsin

26
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What is the visual pigment in rods called?

rhodopsin

27
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What allows colour vision?

cones having different opsin types to absorb light best at a different wavelength

28
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Where are cones most concentrated?

at the fovea

29
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How are rods distributed across the retina?

absent at fovea, numbers greatest beside fovea

30
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Why do we not see blind spots in our vision?

brain interpolates

31
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What type of receptors are visual pigments?

G protein coupled receptors (metabotropic)

32
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Where is the binding site for visual pigments?

chromophore 11-cis-retinal

33
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What does the molecular cascade activated by light result in?

breakdown of cyclic GMP

34
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What is the function of cGMP?

it holds open channels that allow Na+ and Ca2+ in

35
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Why is there a complex cascade system?

for amplification

36
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What does light adaptation do?

allows us to cope with constant background light by producing more cGMP

37
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Why is daytime vision dependent on cones?

rods break down cGMP faster

38
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Why do cones signal fast events and rods slow?

recovery rate is faster in cones

39
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What is the receptive field (RF)?

set of photoreceptors that RGC gets info from

40
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What are the two parts of RFs?

centre (direct), surround (indirect)

41
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Where are the smallest RFs?

fovea

42
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What do large RFs and small RFs do?

small: high visual acuity, large: signals object presence