ELM 7.1

Question 1

The component of the eye that produces the greatest refraction is the:

Answer 1

cornea

the cornea accounts for about 2/3 of the refractive power of the eye - large degree of refraction produced by the cornea is because light enters it from a gaseous phase

Question 2

A visual protein is composed of one molecule each of

Answer 2

opsin and retinal

the visual proteins are members of the retinylidene protein family
in vertebrates, the members of this family are the G protein coupled receptors
the retinal can be regarded as a light activated agonist of the receptor - when it is struck by light of the correct wavelength, the retinal undergoes an isomerisation from cis to trans form (in vertebrates)
the wavelength of light that the retinal is sensitive to depends on the exact amino acid sequence of the opsin protein that is present

Question 3

To which group of proteins does rhodopsin belong?

Answer 3

g protein coupled receptors
rhodopsin is a member of the g protein coupled receptor superfamily - 7 transmembrane domains

Question 4

mice with inactive melanopsin genes would have disturbances in their

Answer 4

circadian rhythm
melanopsin the visual pigment present in photosensitive ganglion cells

these cells are involved in the pupillary reflex and in entrainment of circadian rhythms to light and dark periods - not invovled in vision

Question 5

the primary visual cortex is located in which lobe?

Answer 5

occipital

Question 6

the sequence of events that occurs following light exposure of a vertebrate rod/cone photoreceptor is: (opsin activation, closure of cGMP-gated chennels, depolarization/hyperpolarization)

Answer 6

opsin activation, closure of cGMP-gated channels, hyperpolarization

Question 7

light may be described both as an _______ and as a bunch of _____

Answer 7

electromagnetic wave
photons

Question 8

large amplitude means ___ light

Answer 8

bright

Question 9

myopia

Answer 9

short-sightedness

Question 10

hyperopia

Answer 10

far-sightedness

Question 11

What kind of lens do you need for myopia?

Answer 11

concave

Question 12

what kind of lens do you need for hyperopia?

Answer 12

convex lens

Question 13

what order from outside to in
rods
horizontal cells
cones
amacrine cells
bipolar cells
retinal ganglion cells

Answer 13

rods
cones
horizontal cells
biopolar cells
amacrine cells
retinal ganglion cells

Question 14

glutamatergic excitatory neurons

Answer 14

rods
cones
bipolar cells
retinal ganglion cells

Question 15

RPE

Answer 15

pigmented layer at the back of the retina

Question 16

what is RPE essential for?

Answer 16

recycling of retinaldehyde, thus maintaining function of rods and cones
helps rods and cones to cope with oxidative stress

Question 17

most cones are in the _____ where we have max _____. this area is blind at ______

Answer 17

fovea
visual activity
night

Question 18

what is the role of rods

Answer 18

night vision and peripheral vision

Question 19

which are more sensitive - rods or cones?

Answer 19

rods - 1000 times more sensitivie

Question 20

describe opsin

Answer 20

GPCR with 7 transmembrane domains
different opsins in 3 types of cones, rods, and melanopsin RGCs (5 opsins)

Question 21

retinal (_____ for every opsin) describe

Answer 21

same
vitamin A derivative
absorbs light and changes conformation (bleaching)

Question 22

in the dark, photorecptors are ______ when _____ are open

Answer 22

depolarized
sodium channels

Question 23

in the light, _______ close, leading membrane ______

Answer 23

sodium ion channels
hyperpolarization

Question 24

when the membrane is depolarized, there is _____ release

Answer 24

glutamate

Question 25

_____ absorbs light and changes conformation. this results in the ______ of sodium channels and _______

Answer 25

retinal
closure
hyperpolarization

Question 26

what is the order of these things ?
1 photon of light
2 activation of transducin
3 reduction in cGMP
4 closure of sodium channels
5 conformational change in rhodopsin molecule
6 activation of phosphodiesterase

Answer 26

1, 5, 2, 6, 3, 4

Question 27

describe horizontal cells (3)

Answer 27

light intensity adaptation
spatial processing
colour processing (opponency)

Question 28

describe amacrine cells (4)

Answer 28

• directional motion
• modulate light adaptation
• modulate circadian rhythm
• sensitivity of night vision

Question 29

describe retinal ganglion cells RGC (3)

Answer 29

• further process colour, motion, and shapes
• the ONLY output cells, fire action potentials
• some RGCs (intrinsically photosensitive retinal ganglion cells) can detect light via melanopsin

Question 30

melanopsin doesn’t contribute to image formation, but affects: (3)

Answer 30

• circadian rhythms
• pupil size
• body temp