21.2 NS: Retina

Question 1

Where do we get visual acuity at:
Photopic
Scotopic

light levels?

Answer 1

Photopic: fovea, cones

Scotopic: 5-15 degrees-rods

Question 2

How many cones and rods do we have?

Answer 2

Cones: 5 million
Rods: 100 million

Question 3

What are bipolar cells important for? What NTM do they release?

Answer 3

Spatial, colour vision- glutamate

Question 4

What are horizontal cells and what do they do in response to light?

Answer 4

Lateral inhibition

Hyperpolarise to light (with GABA)

Question 5

What are amacrine cells important for? Are they excitatory or inhibitory

Answer 5

Lateral inhibition (inhibitory)

Question 6

What do ganglion cells release? What types are there?

Answer 6

Release glutamate

ON, OFF, M and P cells

Question 7

What is the receptive field of a ganglion cell?

Answer 7

Area of retina that changes cell’s membrane potential with light

Question 8

What do photoreceptors do in response to light? With what NTM?

Answer 8

Light=graded changes in membrane potential, hyperpolarise (glutamate)

Question 9

What happens to photoreceptor channels in the dark?

Answer 9

cGMP gates a sodium channel=influx of Na+ ions

Question 10

What do OFF and ON bipolar cells do? They are each ~tropic

Answer 10

OFF: hyperpolarise to light (metabotropic, mGlu6)

ON: depolarise to light (ionotropic)

Aka they have different glutamate receptors

Question 11

What is the central vs. surround response in the retina?

Answer 11

Central: through pathway determines (Ph-BC-GCs)

Surround: HC input

Question 12

What occurs in melanoma associated retinopathy?

Answer 12

Antibodies to ON bipolar cells= ‘flickering lights’, water splashing over L eye