Ch 9: the eye

Question 1

conjunctiva

Answer 1

mucous membrane that covers front of eyes and lines inside of eyelids

Question 2

three eye layers

Answer 2

fibrous, vascular, retinal

Question 3

sclera

Answer 3

white layer of dense connective tissue

Question 4

cornea

Answer 4

transparent coat that covers the iris

Question 5

choroid

Answer 5

highly vascularized internal lining of sclera

Question 6

ciliary body

Answer 6

anterior vascular layer

Question 7

iris

Answer 7

colored portion of eye

Question 8

pupil

Answer 8

hole in center of iris

Question 9

dilation

Answer 9

regulated by sympathetic neurons

Question 10

constriction

Answer 10

regulated by parasympathetic neurons

Question 11

macula lutea

Answer 11

yellow spot at retinal posterior

Question 12

fovea centralis

Answer 12

contains only cones; highest resolution

Question 13

optic disc

Answer 13

exit site of optic nerve (blind spot)

Question 14

vitreous humor

Answer 14

fills space between retina and lens

Question 15

diopter

Answer 15

reciprocal focal distance; measure of refractive power

Question 16

accomodation

Answer 16

ability to change refractive power of lens

Question 17

visual field

Answer 17

total amount of space that can be viewed by the retina when the eye is fixed straight ahead

Question 18

visual acuity

Answer 18

ability to distinguish two nearby points

Question 19

horizontal cells

Answer 19

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

Question 20

amacrine cells

Answer 20

receive input from bipolar cells and project to ganglion cells, bipolar cells, or other amacrine cells

Question 21

rods

Answer 21

• 92 million/retina
• 1000 times more sensitive than cones
• vision in dim light
• black and white vision

Question 22

cones

Answer 22

• 5 million/retina
• vision in bright light
• color vision

Question 23

central vision

Answer 23

• greater resolution in daylight
• blind in dim light
• better in discriminating colors

Question 24

peripheral vision

Answer 24

more sensitive in dim light

Question 25

photopigments

Answer 25

- opsin portion: 7 transmembrane GPCRs - retinal portion: light absorbing area

Question 26

phototransduction

Answer 26

conversion of light energy to membrane potential

Question 27

phototransduction (dark)

Answer 27

- outer segments of the rod are depolarized in the dark - guanylyl cyclase produces cGMP - cGMP opens Na+ channels, causing Na+ inflow (depolarization) - ca2+ remain open - ca2+ influx triggers glutamate release - glutamate causes inhibition of postsynaptic potential

Question 28

phototransduction (light)

Answer 28

- light causes conformational change of cis-retinal to trans-retinal - trans-retinal separates from opsin - transducin is activated - transducin activates cGMP phosphodiesterase, degrades cGMP - cGMP-gated Na+ channels close, causing hyperpolarization - Ca2+ channels close, decreasing Ca2+ influx - glutamate release is shut off - bipolar cells are activated and stimulate ganglion cells

Question 29

_________ cells receive input

Answer 29

bipolar

Question 30

_________ cells fire APs

Answer 30

ganglion

Question 31

direct input pathway

Answer 31

light → photoreceptors → bipolar cells

Question 32

indirect input pathway

Answer 32

light → photoreceptor cells → horizontal cells → bipolar cells

Question 33

receptive field

Answer 33

provides direct input

Question 34

receptive surround

Answer 34

provides indirect input

Question 35

M-type cells

Answer 35

- 5% - conduct APs more rapidly

Question 36

P-type cells

Answer 36

90%

Question 37

nonM-nonP-type cells

Answer 37

5%

Question 38

ipRGCs

Answer 38

- use melanopsin as photopigment - depolarize to light - involved in circadian rhythms

Question 39

in the eye, the ______ and lens refract light rays to focus them on the retina.

Answer 39

cornea

Question 40

the sympathetic nervous system stimulates contraction of _______ muscles and ______ the pupil's size.

Answer 40

dilator pupillae; increases

Question 41

the parasympathetic nervous system stimulates contraction of _______ muscles and ______ the pupil's size.

Answer 41

sphincter pupillae; decreases

Question 42

sequence of visual information transfer in the retina

Answer 42

photoreceptors → bipolar cells → ganglion cells

Question 43

which part of the photoreceptors contains photopigments?

Answer 43

outer segment (discs and folds)

Question 44

light stimulus _______ glutamate release from photoreceptors and induces _______ of ON bipolar cells.

Answer 44

decreases; depolarization

Question 45

light stimulus _______ glutamate release from photoreceptors and induces _______ of OFF bipolar cells.

Answer 45

decreases; hyperpolarization