MNSR 32 - Structure of Eye and Photoreceptors Flashcards

1
Q

what type of organ is the eye

A

sensory

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2
Q

function of eye

A

converts light energy into electrical signals using photoreceptor cells

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3
Q

name the 6 extraocular muscle that holds the eye in place

A

4 recti - superior, lateral, medial, inferior

2 oblique - inferior, superior

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4
Q

how is the eye connected to the brain

A

connected to brain by optic II cranial nerve

goes from back of the eye - innervates muscle to move and focus the eye

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5
Q

name the 2 fibrous layers of the eye

A

sclera

cornea

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6
Q

sclera

A

avascular
white and opaque outer layer
gives shape and structure, strength and protection

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7
Q

cornea

A

in sclera layer at the front of the eye
transparent region
allows light in the eye
provides 2/3 of human eyes focusing power

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8
Q

are the chances of the body rejecting a cornea in a cornea transplant high? why or why not?

A

the chances of it getting rejected are low - no blood vessels

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9
Q

second layer of the eye

A

uvea - vascularised

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10
Q

features of uvea

A

rich in blood vessels to provide oxygen and nutrients

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11
Q

features and function of choroid

A

contains blood vessel - to provide oxygen and nutrients
rich in melanin
light rays won’t get detracted in the eyes

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12
Q

function of ciliary body

A

ring shaped muscle surrounding the pupil

alter the shape of lens

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13
Q

3rd layer of eye

A

sensory tunic

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14
Q

2 layers in sensory tunic

A

epithelial layer - outer pigmented layer

neural layer - inner light sensitive, contains photoreceptors

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15
Q

where is aqueous humour found

A

between cornea and the lens

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16
Q

where is vitreous humour

A
  • found in between lens and retina
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17
Q

macula

A

back of the eye in the retina

large conc of photoreceptor cells - gives high res. colour vision

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18
Q

damage to macula can lead to ..

A

macular degeneration

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19
Q

how is blindspot created?

A

optic disk in retina that is the entry point for blood vessels and nerves w/o photoreceptor cells

20
Q

histology of the retina

A

outer pigmented epithelial layer is thin and contains a lot of melanin
inner neural layer contains 3 neurons - photoreceptors, bipolar cells and ganglion cells

21
Q

2 photoreceptor cells

A

rods - slender and numerous

cone - less numerous and broader body

22
Q

where are cones found in the retina?

A

in the centre

23
Q

location of rods in retina?

24
Q

why do we fail to see colour in dim light?

A

cones - for colour, have low sensitivity in dim light

25
2 lateral interneurons and their function
horizontal - help w/ passing of light photoreceptor to bipolar amacrine - - pass light from bipolar cells to ganglion cells
26
histology of retina
go back to it in slide 12
27
max scotopic vision rods
maximal at 507 nm - greys and silver
28
max. photopic vision- cones
555
29
are eyes fully or slowly adapted
slowly take 30-60 minutes to be fully adapted
30
what is rhodopsin and what is its function?
protein opsin + cofactor 11 cis retinal photon - 11 cis retinal -> 11 trans retinol - change in conformation of membrane as cofactor leaves activates opsin sends stimulus to nerve
31
what makes rhodopsin sensitive to light
11 cis retinal derived from 11-trans-retinol, vitamin A
32
deficiency of vitamin A can lead to...
A deficiency of vitamin A leads to night blindness and eventual deterioration of the outer segments of the rods
33
visual cycle
go back to it slide 17
34
what does colour vision require for good visual detail?
require good illumination for good visual detail - photopic vision
35
fovea
small depression in retina contains only cones
36
ratio of rods to cones of each 900,000 optic fibres
follows that on average 140 rods and 6 cones converge on each optic fibre
37
wavelength to pick up blue red and green cones
blue - 400 - 530 nm green cone - 440 - 610 red cone - 580 - 690 nm
38
who introduced the colour vision theory and later expanded the theory
Thomas Young | Expanded later by the German physiologist von Helmholtz
39
Young - Helmholtz or Trichromatic theory
The theory proposed that there are three different types of cone in the retina sensitive to blue, green and red light respectively
40
cones to perceive the colour orange and yellow
red and green cones
41
cones to perceive the colour white
all red, green and blue cones
42
what muscles in the eye control horizontal movements|?
Horizontal movements are controlled entirely by the medial and lateral rectus muscles
43
what muscles control vertical movement?
the superior inferior rectus muscles, 2 oblique muscles.
44
unconscious eye movement relates to what reflex
vestibule ocular reflex - relates to ear vestibular nerve
45
how do muscles move in response to bright light?
pupillary sphincter contracts and reduces pupil size
46
how do muscles move in response to dim light?
pupillary dilator contracts, increases pupil size
47
what tool is used to test a a persons ability to distinguish colour and therefore detect colour blindness
Ishihara colour cards