Vision

Question 1

Where is vitreous humour

Answer 1

Behind the lens

Question 2

Where is aqueous humour

Answer 2

In front of the lens

Question 3

Flow of aqueous humour

Answer 3

Produced in the posterior chamber which is behind the iris and flows through the pupil to be absorbed in the anterior chamber
This humour is to nourish the cornea as it is avascular to prevent reduction in the visual field

Question 4

Causes and treatments of glaucoma

Answer 4

2 types
Angle closure where the iris and cornea become attached blocking the reabsorption of the fluid
Open angle - where the reabsorption is prevented by the thickening of the venous vessels
Treatment
Closed angle surgery
Open angle beta blockers stop secretion and prostaglandins to promote drainage

Question 5

What is the direct pathway of light

Answer 5

Photoreceptor -> bipolar -> ganglion

Light has to pass through the other cells before it reaches the photoreceptor at the back of the retina

Question 6

What is the indirect pathway

Answer 6

Where the amacrine and horizontal cells modulate the transmission of light

Question 7

Types of photoreceptor

Answer 7

Rods

Cones

Question 8

What photopigment do rods contain

Answer 8

Rhodopsin on inner cell disks

Question 9

Pigment of cones

Answer 9

Opsins - green red and blue

Found in the infolding of the surface membrane

Question 10

What does the fovea contain

Answer 10

Cones

Question 11

What does the peripheral retina contain most -

Answer 11

Rods

Question 12

What are rods most sensitive to and what are they most useful for

Answer 12

Light

Night vision

Question 13

Cones most sensitive to and what are they most useful for

Answer 13

Colour vision without light colour cannot be distinguished

Question 14

Rod to ganglion ratio and the cone to ganglion ratio

Answer 14

Rod ratio is many to one this means that it has low visual acuity but high sensitivity to light of one rod is not as activated by light as the other the the ganglion cell can be activated anyway

Cone to ganglion ratio is 1:1
This means high visual acuity but low sensitivity

Question 15

What happens at the rods on the dark

Answer 15

Rhodopsin is not activated G protein is inactivate -bound to GDP
This means that PDE is inactive so cannot converts cGMP to GMP which means the cGMP gated cation channel is still active so the cell depolarises
This means there is glutamate release and can synapse with a bipolar cell

Question 16

What happens to rods in the dark

Answer 16

Rods absorb the light changes from 11-cis. -> all trans
This activates the G protein which then becomes bound to GTP this activates PDE this then converts cGMP to GMP so the cGMP gated channels can no longer open so the cell hyperpolarises

Question 17

What do bipolar ON cells do

Answer 17

In the dark: glutamate causes he
Hyperpolarisation
In the light : lack of glutamate causes causing depolarisation

Question 18

What do bipolar OFF cells do

Answer 18

In the dark they depolarise -> glutamate

In the light they hyperpolarise -> Dec glutamate

Question 19

Transection at optic tract

Answer 19

Homonymous hemianopia

Question 20

Transection at optic nerve

Answer 20

Blindness in one eyes

Question 21

Transection at optic chiasm

Answer 21

Bitemporal hemianopia