7 Vision

Question 1

What might cause glaucoma?

Answer 1

angle closure (iris adheres to cornea blocking off reabsorption)
open angle (sclerosis of veins)

Question 2

How might glaucoma be treated?

Answer 2

maybe surgery
beta-blockers
prostaglandin analogues

Question 3

How do beta-blockers help treat glaucoma?

Answer 3

decrease production of aqueous humour

Question 4

How do prostaglandin analogues help treat glaucoma?

Answer 4

increase blood drainage

Question 5

What do horizontal and amacrine cells do?

Answer 5

modulate transmission of information and enable lateral transmission

Question 6

Where are photopigments in rods and cones?

Answer 6

intracellular discs

Question 7

What is the effect of the arrangement of discs in rods?

Answer 7

way way more
more sensitive to light
cones need higher light levels to work

Question 8

What are the 3 different types of opsins in cones?

Answer 8

I blue
II red
III green

Question 9

What happens to the proportion of cones as you reach the fovea?

Answer 9

increases, until ultimately it’s all cones

Question 10

Where is the blind spot?

Answer 10

where the optic nerve leaves the eye

Question 11

What is the significance of rod and ganglion cell arrangement?

Answer 11

many rods to 1 ganglion cell

in low light summation to ganglion cell allows response

Question 12

What is the significance of cone and ganglion cell arrangement?

Answer 12

1:1
high acuity
takes a lot to stimulate the ganglion cell

Question 13

What is inactive Rhodopsin made out of?

Answer 13

Retinal

Opsin

Question 14

What is retinal?

Answer 14

chromophore

vitA derivative

Question 15

What is Opsin?

Answer 15

GPCR

Question 16

What is the state of rods in the absence of light?

Answer 16

cGMP-gated channels open

Na+ influx causes depolarisation

Em=-30mV

causes glutamate release across synapse with bipolar cell

Question 17

What the the overall effect of light exposure on the rod?

Answer 17

hyperpolarisation

decreased glutamate release

Question 18

What happens to retinal when light hits it?

Answer 18

11cis->all-trans

Question 19

What happens to opsin under light?

Answer 19

activated

Question 20

What does active opsin do?

Answer 20

binds GTP, the G-protein then activates PDE

Question 21

What does the activation of PDE do?

Answer 21

cGMP breakdown
channel closure
hyperpolarisation

Question 22

What is the direct pathway of retinal transmission?

Answer 22

photoreceptor > bipolar cell > ganglion cell…

Question 23

What are the 2 states of bipolar cells and ganglion cells?

Answer 23

ON

OFF

Question 24

When are ON cells depolarised?

Answer 24

in light

Question 25

What happens to OFF cells in light?

Answer 25

hyperpolarisation

Question 26

What happens to ON cells in the dark?

Answer 26

glutamate released from photoreceptor

hyperpolarisation

Question 27

What happens to ON cells in the light?

Answer 27

decreased glutamate

depolarisation

Question 28

What happens to OFF cells in the dark?

Answer 28

glutamate released from photoreceptor

depolarisation

Question 29

What happens to OFF cells in light?

Answer 29

decreased glutamate

hyperpolarisation

Question 30

What accounts for the different resopnses to light from ON and OFF cells?

Answer 30

different glutamate receptors

Question 31

What is the principle of the indirect pathway?

Answer 31

each bipolar or ganglion cell has a receptive field

central part (involved direct communications from photoreceptor)
Surround part (indirect connections via horizontal/amacrine cells)