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BMS11004 > BMS11004 WEEK 8 - TUESDAY > Flashcards

BMS11004 WEEK 8 - TUESDAY Flashcards

retina, phototransduction, image formations

1
Q

what is importance of vision

A

detect prey, predator, mates
communication

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2
Q

name 3 words which describe light

A

visible electromagnetic radiation

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3
Q

what is wavelength

A

distance between peaks/troughs

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4
Q

what is frequency

A

number of waves per second

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5
Q

what is amplitude

A

difference between wave peak and trough

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6
Q

how does electromagnetic light travel

A

straight lines/rays until interact with atoms/molecules

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7
Q

what 3 ways can light rays interact

A

reflection, absorption, refraction

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8
Q

describe reflection

A

hits wall, and bounces off

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9
Q

describe absorption of light ray

A

hits wall, it is absorbed by wall
photoreceptors and pigmented epithelium of retina

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10
Q

describe refraction of light ray

A

hit wall, is bend and leaves at diff angles
bends due to difference in speed of light through different media

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11
Q

explain monocular vision

A

one eye either side of head, large visual field = prey

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12
Q

explain binocular vision

A

eyes facing out front of head, allow measurements of depth perception = predator

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13
Q

what does the pupil do

A

let light inside eyes

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14
Q

what does iris do

A

contain muscles that controls amount of light entering eye

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15
Q

what does cornea do

A

glassy, transparent covering of pupil and iris that refracts light

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16
Q

what does sclera do

A

continuous with cornea, forms tough protective wall of eyeball to give it its shape

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17
Q

what does extraocular muscles do

A

move eyeball, controlled by oculomotor nerve (cranial nerve III)

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18
Q

what does optic nerve do

A

carries axon from retina to brain (cranial nerve II)

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19
Q

what does retina do

A

contain sensory receptor cells and afferent neurons

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20
Q

what does lens do

A

suspended by zonal fibres (suspensory ligaments) which are attached to ciliary muscle, enabling lens stretch

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21
Q

what is opthalmoscopes

A

shine light into eye and look at back of eye

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22
Q

what is optic disk/blind spot

A

origin of blood vessels and optic nerve, cannot sense light

23
Q

what is macula

A

close to midline of nasal retina and temporal retina, for central vision
devoid of large blood vessels to improve vision quality

24
Q

what is fovea

A

retina is thinnest here, area of highest visual acuity
when not using fovea, side area of visual field = peripheral vision

25
Q

where should light rays be focused

A

onto retina, ideally onto fovea

26
Q

where do refraction occur

A

at cornea = 80%
lens 20%

27
Q

what determines degree of refraction

A

difference in refractive indice between 2 media, and angle at whicb light hits interface between 2 medias

28
Q

outline refractive index

A

measure of speed of light within it
light moves quicker through air than cornea due to increased density of cornea

29
Q

what cause refraction by cornea

A

light arrive at cornea via air, but cornea is mainly water and light travel slower water>air due to higher density, so cause refraction

30
Q

outline focal distance

A

distance from refractive surface to convergence of parallel light rays

31
Q

if light hits cornea directly perpendicular, what happens

A

move straight through onto retina

32
Q

explain refraction of light of images for distant/close objects through the cornea

A

distant = almost parallel light ray so cornea provides sufficient refraction to focus them onto retina
closer = light ray not parallel, require additional refraction to focus them onto retina, provided by fattening of lens

33
Q

what does rounding of lens allow for focusing objects

A

increases refractive power to focus closer objects onto fovea

34
Q

explain when eye is emmetropic

A

when lens is flat and focusing on distant objects

35
Q

what is farsightedness (hyperopia)

A

eye too short and near objects focused behind retina, not enough refraction

36
Q

how can we fix farsighedness/hyperopia

A

convex glasses, make light coming from near object parallel

37
Q

explain shortsightedness/myopia

A

eye too long so distant objects focused before retina, too much refraction
sees close up but not far away

38
Q

how is myopia fixed

A

concave lense

39
Q

what muscles contract to allow lens changing

A

contraction/relaxing ciliary muscles

40
Q

how is light focused onto retina converted into neural or electrical activity

A

photons pass through ganglion or bipolar cells before reaching photoreceptors, absorbed by pigmented epithelium

41
Q

name main retinal cell

A

ganglion cells
bipolar cells
photoreceptors

42
Q

name other retinal cells

A

amacrine cells (modulate info transfer between ganglion cells, bipolar
horizontal cells (modulate info transfer between photoreceptors, bipolar)

43
Q

describe what ganglion cell do

A

output from retina

44
Q

explain what bipolar cells do

A

connect photoreceptors to ganglion cells

45
Q

explain what photoreceptors do

A

sensory transducers (rods and cones)

46
Q

outline the duplicity theory of photoreceptors

A

can’t have high sensitivity and resolution in single receptor so needs separate system for monochrome and colour = rod, cone

47
Q

outline structure of rod photoreceptors

A

greater number of disk
higher photopigment conc
1000x more sensitive to light than cones

48
Q

what type of vision does rod enable

A

enable scotopic (low light) vision = night time
low visual acuity/resolution

49
Q

explain structure of cone photoreceptors, what type of vision they allow

A

fewer disks, used during daylight (photopic), enabling colour vision
high visual acuity/res, low sensitivity

50
Q

when are rods and cones used together

A

in intermediate (mesopic) light

51
Q

does fovea contain more cones/rods, and what does this allow?

A

most of cones, no rods, allow low convergence on retinal ganglion cells so better for higher res vision

52
Q

what is convergence, sensitivity and resolution like on central retina

A

low convergence
low sensitivity
high resolution

53
Q

what is convergence, sensitivity, resolution like on peripheral retina

A

high convergence
high sensitivity
low resolution

BMS11004 (29 decks)

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