Physiology of Retina and Vision

Question 1

what 4 things must happen in order to see an object

Answer 1

1. pattern of object must call on vision receptors (rods and cones in retina)
2. the amount of light entering the eye must be regulated
3. the energy waves of photons of light must be transduced to electrical signals
4. the brain must receive and interpret the signals

Question 2

what is the direct (vertical) pathway for signal transmission in the eye

Answer 2

photoreceptors — bipolar cells — ganglion cells

Question 3

what are the lateral connections in the retina which influence signal processing

Answer 3

horizontal cells

amacrine cells

Question 4

what do horizontal cells do

Answer 4

receive input from photoreceptors and project to other photoreceptors and bipolar cells

Question 5

what do amacrine cells do

Answer 5

relieve input from bipolar cells and project to ganglion cells, other amacrine cells and other bipolar cells

Question 6

what does a photoreceptor cell do

Answer 6

converts electromagnetic radiation into neural signals (transduction)

Question 7

what are the 4 main regions of photoreceptors

Answer 7

outer segment (cone/rod bit)
inner segment
cell body
synaptic terminator

Question 8

what are the 2 types of photoreceptor

Answer 8

rods and cones

Question 9

what happens to the resting membrane potential of photoreceptors on light exposure (it is usually depolarised but more polarised than normal)

Answer 9

it hyper polarises (becomes even more negative)

Question 10

what happens when photoreceptors depolarise

Answer 10

the rest of transmitter release is reduce, and the decrease in Na+ with light and lack of signals enables the brain to perceive objects in the visual field

less glutamate is release