Lecture 6 mono sensory vision: photoreceptors

Question 1

when a threshold for an action potential is reached, a cell becomes ______, causing a change in membrane potential and _______ of neurotransmitter.

Answer 1

depolarized, release

Question 2

What is the threshold for a photoreceptor action potential?

a) 1000nm/mm2
b) 1000 quanta packets/photoreceptor
c) generally lower than the threshold for a bipolar cell action potential
d) generally higher than the threshold for a bipolar cell action potential
e) none of the above

Answer 2

trick question! photoreceptors to not have action potentials, they do however have a difference in membrane potential, the photoreceptor becomes hyperpolarized. These are slow GRADED POTENTIALS.

Question 3

a photoreceptor _______ in response to light

a) hyperpolarizes
b) depolarizes

Answer 3

a) hyperpolarizes

Question 4

Horizontal cells ______ in response to light

a) hyperpolarize
b) depolarize

Answer 4

a) hyperpolarize, they always follow what the photoreceptor does

Question 5

_______ cells are the first cells to give an action potential

Answer 5

amacrine, then ganglion cells are the 2nd in line to give an action potential

Question 6

name the 3 cells in the retina that display graded potentials rather than action potentials

Answer 6

photoreceptor, horizontal cells, and bipolar cells

Question 7

of all the cells in the retina, which has the smallest receptive field? and largest?

Answer 7

a photoreceptor has the smallest and horizontal cells have the largest.

Question 8

true or false: photoreceptors and horizontal cells do NOT have on/off receptive fields

Answer 8

true, they have mono-sensitive receptive fields

Question 9

true or false: On/off receptive fields are responsible for allowing “contrast” to be part of our visual experience

Answer 9

true, for example; between text and background, and between different colors