Chapter 10 Pt. 2 (Part 4)

Question 1

why can you immediately see when you move from the dark to the light, but there is a delay in being able to see when you move from the light to the dark?

Answer 1

dark to light: cis retinal is converted to trans, and the rods are bleached. rods are of no use, but the light is strong enough for cones to kick in and you immediately see in color.

light to dark: in full light, the rhodopsin in all of the disks in your rods will be photo bleached. there is not enough light to activate any of the cones.

Question 2

how is it possible that your eyes only have 3 different color photoreceptors, yet you can distinguish millions of colors?

Answer 2

draw

Question 3

less activated opsin means…

Answer 3

less activated transducin

Question 4

the point is not whether glutamate is present or absent, it’s that …. (3)

Answer 4

1. when photoreceptors release different amounts of glutamate, it causes a change in AP frequency in a photoreceptor receptive field
2. each eye constantly sends AP’s from about one million retinal ganglion cells
3. the different patterns received are interpreted as different colors that create different shapes and images in your mind

Question 5

what happens in total darkness compared to light? (2)

Answer 5

some photoreceptors are releasing lots of glutamate onto OFF

other photoreceptors are releasing lots of glutamate onto ON bipolar cells

Question 6

what happens when some photoreceptors are releasing lots of glutamate onto OFF bipolar cells (2)

Answer 6

• bipolar cells are maximally depolarizing RGC’s
• RGC’s are sending high AP frequency signals to the brain

Question 7

what happens when some photoreceptors are releasing lots of glutamate onto ON bipolar cells (2)

Answer 7

• bipolar cells are maximally hyperpolarized and not stimulating their associated RGC’s
• these RGC’s are sending very low or no AP signals to the brain

Question 8

primates have three cones vs only 2 cones for all other mammals. why is this advantageous?

Answer 8

more color means more contrast means more detail means interpret the environment better

Question 9

why do dark rooms typically use a safe light that is red?

Answer 9

we have more red cones. why do we have more red cones? easier to stimulate with high energy blue than low energy red

Question 10

what is binocular vision and what advantage does it provide?

Answer 10

each eye has distinct visual fields but they overlap. this is good for depth perception

Question 11

what would happen if there were equal numbers of each type of cone?

Answer 11

the world would be mostly blue

Question 12

what is optic crossover?

Answer 12

each eye sends info to both hemispheres, so you’re using both hemispheres to interpret what you see

L eye sees something and goes to right side of the brain which controls the right side

Question 13

what factors influence hand/eye coordination?

Answer 13

proprioception