Module 14 - mammalian eye

Question 1

What does amplitude and wavelength show respectively

Answer 1

intensity of light and colour of light

Question 2

what nm range is visible light

Answer 2

380-750 nm

Question 3

diff between cornea and lens in terms of refractive power

Answer 3

cornea is 42D
And lens is 12D
But lens can adjust its shape unlike the cornea

Question 4

Fun toon of aqueous and vitreous humours

Answer 4

fluid filled areas
Allow light through and keep structure of eye

Question 5

What 2 things hold lens in place

Answer 5

zonule fibres
Ciliary musxlea

Question 6

What type of lens needed when looking at something far and close respecfively

Answer 6

Flat and fat

Question 7

Name of short and long sightedness

Answer 7

myopia
Hyperopia

Question 8

What type of lens corrects myopia and hyperopia

Answer 8

myopia = concavw
Hyperopia = convex

Question 9

what does light path have to cross first to get to rods and cones

Answer 9

retinal ganglion cells
amacrine cells (lateral)
bipolar cells
horizontal cells (also lateral)
then gets to cones and rods
(remember information pathway back to brain is the opposite way)

Question 10

what does the retinal pigment epithelium do

Answer 10

layer at very back behind rods and cones
- makes pupil look black
-recycles retinaldehyde
- helps rods and cones deal with oxidative stress

Question 11

where is max visual acuity

Answer 11

fovea
where most cones are
this is blind at night

Question 12

what is opsin

Answer 12

GPCR w/ 7 TM domains
5 diff types (3 cones, a rod type, and melanopsin)

Question 13

what is opsin bound to

Answer 13

retinal (cis when it’s dark, trans when light)

Question 14

cGMP effect on vision

Answer 14

DARK - cGMP present in photoreceptor
opens Na+ channels = depolarised
glutamate released
LIGHT - cGMP broken down to GMP
Na+ channels closed = hyperpolarised
no glutamate released

Question 15

what molecule needs to be activated for cGMP to be broken down

Answer 15

phosphodiesterase

Question 16

phototransduction

Answer 16

Light = cis retinal —> trans retinal
GDP to GTP in transducin
Gprotein dissociates from rhodopsin
and activates PDE
causing cGMP to GMP

Question 17

how many cones do humans have

Answer 17

3 cones - trichromats
RGB
allow colour perception

Question 18

how many cones in most aquatic animals

Answer 18

1
monochromats

Question 19

examples of dichromat animals

Answer 19

dog
reptile
mice
kitty
hors

Question 20

what type of animals cones have most complicated visual system

Answer 20

mantis shrimp
12-16 cone types
use it for communication

Question 21

why men more likely to be colour blind

Answer 21

red and green opsin on X chromosome
and they only have 1
(mostly red green colour blindness)

Question 22

how can some women be tertrachromats

Answer 22

might have 2 red alleles, 1 on each X chrom
usually 1 should get inactivated, but sometimes doesnt and so higher capacity to discriminate colours

Question 23

what chromosome is blue opsin on

Answer 23

chrom 7

Question 24

what are the 2 types of bipolar cells

Answer 24

OFF = bipolar cell is hyperpolarised
ON = bipolar cell is depolarised
(both respond to photoreceptor being hyper or de polarised)

Question 25

functions of horizontal cells

Answer 25

adapting eye to light intensity
spatial and colour processing

Question 26

functions of amacrine cells

Answer 26

directional motion
modulate light adaptation
and therefore circadian rythm
and sensitivity of night vision

Question 27

function of retinal ganglion cells

Answer 27

colour, motion, shape processing
fire APs after recieivng signals from bipolar cells

Question 28

what are ipRGC

Answer 28

they are phtosensitive cuz they have melanopsin
so can detect light intensity

Question 29

function of melanopsin

Answer 29

detects light intensity
- circadian rhythms
- pupil size
-body temp

Question 30

what part of retina crosses to other side of brain, and what part stays on same side of brain

Answer 30

nasal retina - crosses over
temporal retina - stays on same side

Question 31

part of breain that are primary target of retinal gnaglion cells

Answer 31

lateral geniculate nucleus (LGN)

Question 32

where is primary visual cortex

Answer 32

occipital lobe
(aka V1)

Question 33

how does orietnation selectivity work in V1

Answer 33

APs fired differ depending on orientation of visual stimuli