B7.030 Visual System I

Question 1

anterior chamber of the eye

Answer 1

anterior to the pupil
cornea + fluid compartment
location where fluid exits

Question 2

posterior chamber of the eye

Answer 2

between lens and pupil

location where fluid forms

Question 3

result of fluid accumulation

Answer 3

increased intraocular pressure

Question 4

causes of fluid accumulation

Answer 4

overproduction

clogging of drainage

Question 5

sphincter muscle

Answer 5

closes pupil

under parasympathetic control

Question 6

radial muscle

Answer 6

opens pupil

under sympathetic control

Question 7

where does visual signal processing begin

Answer 7

the retina

Question 8

photoreceptors

Answer 8

transduce photons into neuronal activity
final layer of cells in back of the eye
light passes through all other cells first

Question 9

fovea

Answer 9

triangular break in the ganglion and bipolar cell layers so that light has a more direct path to photoreceptors
concentration of cones at this point
aids in visual acuity

Question 10

cell layers of the retina

Answer 10

inner: ganglion
inner plexiform layer
middle: bipolar
outer plexiform layer
outer: photoreceptors

Question 11

function of ganglion cells

Answer 11

axons form the optic nerve (CN II) which travels to the thalamus

Question 12

where are light rays refracted

Answer 12

cornea (static)

lens (dynamic)

Question 13

why are light rays refracted

Answer 13

to be more specifically focused on the retina

bent more when objects are closer

Question 14

how does the shape of the lens change when bending light

Answer 14

rounded when bending light, flat when not

Question 15

result of errors in light refraction

Answer 15

images not focused on the retina

reduced visual acuity

Question 16

hyperopic

Answer 16

far sighted
light converges behind retina
larger patch of photoreceptors activated than is necessary

Question 17

myopic

Answer 17

near sighted

light converges in front of retina

Question 18

astigmatism

Answer 18

two focal points of light convergence

Question 19

2 causes of light refraction errors

Answer 19

funky eyeball shape

inability of lens to change shape adequately

Question 20

presbyopia

Answer 20

lens hardened with age, unable to change shape

image focused behind retina

Question 21

how to correct presbyopia

Answer 21

artificially thicken the lens (glasses, contacts)

refractive lens exchange

Question 22

describe how a map of the external environment is created on the retina

Answer 22

light from a given location in space will stimulate photoreceptors in a specific location in the retina
location in space that stimulates a given photoreceptor is its receptive field

Question 23

why are images on the retina upside down

Answer 23

path that light travels to reach the retina

Question 24

binocular vision

Answer 24

both eyes can focus on the same point in space

Question 25

nasal retina

Answer 25

temporal visual field

Question 26

temporal retina

Answer 26

nasal visual field

Question 27

where is the left half of the visual world processed

Answer 27

right optic tract/ LGN/ visual cortex

Question 28

where is the right half of the visual world processed

Answer 28

left optic tract/ LGN/ visual cortex

Question 29

what happens in the optic chiasm

Answer 29

fibers from the nasal retina (temporal visual field) decussate in order to reach the contralateral side of the brain

Question 30

what is rhodopsin and how does it impact vision

Answer 30

molecules embedded in photoreceptor outer segment membrane disks composed of retinal and opsin absorbs photons on light and isomerizes, creating the active form

Question 31

metarhodopsin II

Answer 31

activated rhodopsin unstable triggers next step in visual transduction pathway eventually recycled by pigment epithelium at the back of the eye

Question 32

how is signal transduced in the photoreceptor

Answer 32

activation of rhodopsin triggers a g protein coupled pathway pathway results in closure of Na+ channels on the outer cell membrane membrane hyperpolarizes when light hits the retina

Question 33

glutamate release in the photoreceptors

Answer 33

occurs with no light depolarizing current is present aka when light is present, glutamate release is reduced

Question 34

2 types of photoreceptors

Answer 34

rods | cones

Question 35

rod system

Answer 35

operates in dim light, can detect a single photon many rods, many bipolars, one ganglion cell (low acuity) sacrifices acuity for sensitivity one type of opsin (monochromatic) found in periphery of retina

Question 36

cone system

Answer 36

operates in bright light (higher threshold for activation) few cones, one bipolar cell, one ganglion cell maximizes acuity found in high density in fovea different opsins sensitive to different wavelengths of light (color vision)

Question 37

retinal pigment epithelium

Answer 37

absorbs extra photons of light appears dark on histo supplies blood to photoreceptors

Question 38

embryologic development of the retinal layers

Answer 38

``` invagination of the optic vesicle results in 2 layers coming into apposition (pigment epithelium and neural retina) may separate (detached retina) ```

Question 39

blood supply to the retina

Answer 39

inner retinal layers are supplied by branches of the central retinal artery - blood vessels obstruct light path to the retina - hemorrhage and hyperplasia can impair visual acuity, result in visual field deficits

Question 40

why do we have conjugate eye movements

Answer 40

so that an object of interest is focused on the fovea of the retina

Question 41

3 cells in retina

Answer 41

photoreceptors bipolar cells ganglion cells

Question 42

photoreceptors

Answer 42

specialized sensory cells | transduce light into transmitter release

Question 43

bipolar cells

Answer 43

receive input from photoreceptors transfer to ganglion cells no action potential

Question 44

ganglion cell

Answer 44

output cells of the retina | axons form the optic nerve headed for LGN

Question 45

neurotransmitter release in retina

Answer 45

amount of neurotransmitter released is proportional to amount of light activating the retinal pigment dark: cells are depolarized, so more neurotransmitter release light: cells become hyperpolarized, so less neurotransmitter release

Question 46

what is the LGN

Answer 46

nucleus in the thalamus contains a map of contralateral visual field from the optic tract laminated structure w 6 layers

Question 47

where do fibers travel once they leave the LGN

Answer 47

separate into 2 bundles to reach primary visual cortex - parietal lobe fibers = inferior visual field - temporal lobe fibers (Meyer's loop) = superior visual field

Question 48

cortical representation of the fovea

Answer 48

large section | located at occipital pole

Question 49

cortical representation of the peripheral regions

Answer 49

represented more anteriorly

Question 50

upper bank of sulcus

Answer 50

inferior region of visual space

Question 51

lower bank of sulcus

Answer 51

superior region of visual space