The visual system

Question 1

What is the function of the retina?

Answer 1

image acquisition

Question 2

What parts of the brain are involved in visual processing and how?

Answer 2

lateral geniculate nucleus- preprocesses visual info
visual cortex- main processing of info

Question 3

What is the ventral stream?

Answer 3

processes WHAT the object is
located in inferior temporal

Question 4

What is the dorsal stream?

Answer 4

processes WHERE the spatial location is
located in posterior parietal

Question 5

What cells in the retina are inhibitory and therefore part of negative feedback?

Answer 5

amacrine and horizontal cells

Question 6

What forms the optic nerve?

Answer 6

axons of ganglion cells

Question 7

What are the first two layers of the retina and what do they do?

Answer 7

muller cells- on entire retina and are very transparent
bipolar cells- expresses glutamate which activates ganglion cells

Question 8

What is the outer plexiform layer?

Answer 8

Synapses between photoreceptors, bipolar cells and horizontal cells

Question 9

What is the inner plexiform layer?

Answer 9

contains the synapses between bipolar cells, ganglion cells and amacrine cells

Question 10

When are rods and cones active? How do they respond to light?

Answer 10

rods are active in dim light and cones are active in bright light
hyperpolarise which decreases membrane potential

Question 11

What does phosphodiesterase do and how is this related to light transduction?

Answer 11

converts cyclic GMP into GMP
when activated levels of cyclic GMP are lower which non-selectively closes channels in the membrane
stops depolarisation

Question 12

How is rhodopsin linked to phosphodiesterase?

Answer 12

rhodopsin conformation is changed by light which activates phosphodiesterase

Question 13

What is the difference between ON and OFF bipolar cells?

Answer 13

ON- depolarise in response to light and express metabotropic glutamate receptors
OFF- hyperpolarise in response to light and express ionotropic AMPA receptors

Question 14

What does center-surround organisation of bipoalr cells mean?

Answer 14

illumination of the center and the surrounding cells will lead to responses in opposite polarities
converge onto one bipolar cell so the ones in the surround will activate via horizontal cells, not directly

Question 15

What are the two major classes of ganglion cells?

Answer 15

parvocellular
magnocellular

Question 16

What are the differences between the two ganglion cell types?

Answer 16

magnocellular has a much larger dendritic tree
parvocellular can distinguish between different colours whereas magnocellular can only detect the brightness
both have center surround organisation