MNSR 32 - Structure of Eye and Photoreceptors

Question 1

what type of organ is the eye

Answer 1

sensory

Question 2

function of eye

Answer 2

converts light energy into electrical signals using photoreceptor cells

Question 3

name the 6 extraocular muscle that holds the eye in place

Answer 3

4 recti - superior, lateral, medial, inferior

2 oblique - inferior, superior

Question 4

how is the eye connected to the brain

Answer 4

connected to brain by optic II cranial nerve

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

Question 5

name the 2 fibrous layers of the eye

Answer 5

sclera

cornea

Question 6

sclera

Answer 6

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

Question 7

cornea

Answer 7

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

Question 8

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

Answer 8

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

Question 9

second layer of the eye

Answer 9

uvea - vascularised

Question 10

features of uvea

Answer 10

rich in blood vessels to provide oxygen and nutrients

Question 11

features and function of choroid

Answer 11

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

Question 12

function of ciliary body

Answer 12

ring shaped muscle surrounding the pupil

alter the shape of lens

Question 13

3rd layer of eye

Answer 13

sensory tunic

Question 14

2 layers in sensory tunic

Answer 14

epithelial layer - outer pigmented layer

neural layer - inner light sensitive, contains photoreceptors

Question 15

where is aqueous humour found

Answer 15

between cornea and the lens

Question 16

where is vitreous humour

Answer 16

• found in between lens and retina

Question 17

macula

Answer 17

back of the eye in the retina

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

Question 18

damage to macula can lead to ..

Answer 18

macular degeneration

Question 19

how is blindspot created?

Answer 19

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

Question 20

histology of the retina

Answer 20

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

Question 21

2 photoreceptor cells

Answer 21

rods - slender and numerous

cone - less numerous and broader body

Question 22

where are cones found in the retina?

Answer 22

in the centre

Question 23

location of rods in retina?

Answer 23

periphery

Question 24

why do we fail to see colour in dim light?

Answer 24

cones - for colour, have low sensitivity in dim light

Question 25

2 lateral interneurons and their function

Answer 25

horizontal - help w/ passing of light photoreceptor to bipolar
amacrine - - pass light from bipolar cells to ganglion cells

Question 26

histology of retina

Answer 26

go back to it in slide 12

Question 27

max scotopic vision rods

Answer 27

maximal at 507 nm - greys and silver

Question 28

max. photopic vision- cones

Answer 28

555

Question 29

are eyes fully or slowly adapted

Answer 29

slowly take 30-60 minutes to be fully adapted

Question 30

what is rhodopsin and what is its function?

Answer 30

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

Question 31

what makes rhodopsin sensitive to light

Answer 31

11 cis retinal derived from 11-trans-retinol, vitamin A

Question 32

deficiency of vitamin A can lead to…

Answer 32

A deficiency of vitamin A leads to night blindness and eventual deterioration of the outer segments of the rods

Question 33

visual cycle

Answer 33

go back to it slide 17

Question 34

what does colour vision require for good visual detail?

Answer 34

require good illumination for good visual detail - photopic vision

Question 35

fovea

Answer 35

small depression in retina contains only cones

Question 36

ratio of rods to cones of each 900,000 optic fibres

Answer 36

follows that on average 140 rods and 6 cones converge on each optic fibre

Question 37

wavelength to pick up blue red and green cones

Answer 37

blue - 400 - 530 nm
green cone - 440 - 610
red cone - 580 - 690 nm

Question 38

who introduced the colour vision theory and later expanded the theory

Answer 38

Thomas Young

Expanded later by the German physiologist von Helmholtz

Question 39

Young - Helmholtz or Trichromatic theory

Answer 39

The theory proposed that there are three different types of cone in the retina sensitive to blue, green and red light respectively

Question 40

cones to perceive the colour orange and yellow

Answer 40

red and green cones

Question 41

cones to perceive the colour white

Answer 41

all red, green and blue cones

Question 42

what muscles in the eye control horizontal movements|?

Answer 42

Horizontal movements are controlled entirely by the medial and lateral rectus muscles

Question 43

what muscles control vertical movement?

Answer 43

the superior
inferior rectus muscles,
2 oblique muscles.

Question 44

unconscious eye movement relates to what reflex

Answer 44

vestibule ocular reflex - relates to ear vestibular nerve

Question 45

how do muscles move in response to bright light?

Answer 45

pupillary sphincter contracts and reduces pupil size

Question 46

how do muscles move in response to dim light?

Answer 46

pupillary dilator contracts, increases pupil size

Question 47

what tool is used to test a a persons ability to distinguish colour and therefore detect colour blindness

Answer 47

Ishihara colour cards