8.4 Vision

Question 1

3 layers of the eye

Answer 1

1. outer fibrous (cornea and sclera)
2. middle vascular (choroid, iris, ciliary body)
3. inner neural (retina)

Question 2

importance of the aqueous humor

Answer 2

necessary for providing nutrients to the lens and cornea

creates refractive power for the eye

Question 3

aqueous humor is produced by

Answer 3

ciliary body

Question 4

what is the total refractive power of the eye? (lens+cornea)

Answer 4

59 Diopters (D=1/meter)

Question 5

refractive power of the cornea?

Answer 5

42 Diopters

Question 6

refractive power of the lens?

Answer 6

17 Diopters

Question 7

light rays from distant objects are

Answer 7

nearly parallel

so we dont need a lot of refraction

Question 8

what happens to the ciliary muscles/lens/ligaments when you are looking at a distanced object?

Answer 8

ciliary muscles relax
ligamentss tense
lens is flat

Question 9

ciliary muscle is under _________ control

Answer 9

Parasympathetic

Question 10

describe what Muller cells are

Answer 10

long glial cells that stretch almost the entire length of the retina

Question 11

function of Muller cells?

Answer 11

• regulating K+ levels in the extracellular enviroment
• NT uptake
• glycogen storage for energy
• electrical insulation
• protection for neurns

Question 12

what is the importance of the pigmented layer of the Retina?

Answer 12

• absorbs extra light
• allows transport of vitamin A, Cl- and water
• converts all-trans-retinal to 11-cis-retinal for delivery to the photoreceptors

Question 13

layers of the retina

Answer 13

1. pigmented
2. photoreceptors
3. outer limiting
4. outer nuclear
5. outer plexiform
6. inner nuclear
7. inner plexiform
8. ggl
9. nerve fibers
10. inner limiting

Question 14

Rods are responsible for

Answer 14

detect light

Question 15

why are Rods extremely sensitive to light?

Answer 15

they have high amount of Rhodopsin

Question 16

why Rods have low acuity?

Answer 16

many Rods synaps on a single bipolar cell

Question 17

where can we find Rods?

Answer 17

peripheral part of the retina

Question 18

Cones are responsible for

Answer 18

color vision

Question 19

why Cones have high acuity?

Answer 19

only a few Cones synaps on a bipolar cell

Question 20

where can we find Cones?

Answer 20

primarly located in the macula with the fovea having the highest density of cones

Question 21

where is the point of highest visual acuity and why?

Answer 21

fovea

one Cone synapses with one bipolar cell

Question 22

why do Rods have low acuity?

Answer 22

many rods synaps on one bipolar cell

Question 23

what is tne main location of Rods?

Answer 23

primarly in the peripheral parts of the retina

Question 24

why cones are less sensitive to light?

Answer 24

less rhodopsin -> several hundreds photons are needed in order to activate it

Question 25

what are the types of cones?

Answer 25

red green blue

Question 26

what happens when light hits the rodes?

Answer 26

it hyperpolarize the cell due to closure of Na+ Channels

Question 27

what happens when light hits Rhodopsin?

Answer 27

11-cis-retinal -> all-trans-retinal

Question 28

what happens after we generate all-trans-retinal?

Answer 28

series of steps with Opsin to lead to the creation of MetaRhodopsin II

Question 29

what is the job of MetaRhodopsin II?

Answer 29

activates Transducin

Question 30

what is the job of Transducin?

Answer 30

stimulated Phosphodiesterase

Question 31

what is the job of Phosphodiesterase?

Answer 31

breaks down cGMP -> 5'GMP

Question 32

what happens when levels of cGMP goees down?

Answer 32

there is no more cGMP to activate the cGMP dependant Na+ and Ca++ Channels -> Hyperpolarization will occur

Question 33

what will the decrease Glu release do to Ionotropic Receptors?

Answer 33

decreased excitatory Glu response -> Hyperpolarization of bipolar and horizontal cells -> Inhibition

Question 34

what will the decrease Glu release do to Metabotropic Receptors?

Answer 34

decreased Inhibatory Glu response -> Depolarization of bipolar and horizontal cells -> Excitation