Visual System

Question 1

optic disk

• produces
• exit of…

Answer 1

produced blind spot

exit of optic nerve

Question 2

macula lutea

-contains

Answer 2

central fovea (pit)

Question 3

components of retina

Answer 3

optic disc

macula lutea

Question 4

cell layers of retina

Answer 4

pigment cell layer
layer of rods and cones
ganglion cell layer

Question 5

retina: pigment cell layer
- derived from
- attaches retina to…
- absorbs…

Answer 5

derives from choroid
attaches to eyeball
absorbs stray light

Question 6

rods

• location
• function

Answer 6

periphery of retina
function
-low light vision
-perception of movement

Question 7

cones

-location

Answer 7

central retina

Question 8

what is the name for the structure that contains only cones that is the area of maximum visual acuity, color, and brightness discrimination

Answer 8

fovea

Question 9

retina: ganglion cell layer
- _____ of these cells form the _____
- _____ are described for ganglion cells

Answer 9

myelinated axons of these cells form the optic nerve

receptive fields are described for ganglion cells

Question 10

in the normal eye, a _____ image of the object is focused on the retina

Answer 10

inverted

Question 11

light is refracted by the…

-which parts inverts the image?

Answer 11

cornea
aqueous humor
lens (where image is inverted)
vitreous humor

Question 12

lens

• function
• how does this occur?
• -what is this called

Answer 12

changes the refractive power of the eye
accomplished by changing the shape fo the lens
-called accommodation

Question 13

how does the lens shape change for

• close viewing
• distant viewing

Answer 13

rounder for close viewing

flatter for distant viewing

Question 14

accommodation

-to view a near object, the lens must _____ its refractive power by becoming _____

Answer 14

increase by becoming more convex (rounder)

Question 15

at rest, how is the lens held in a relatively flat shape?

Answer 15

suspensory fibers that connect it to the ciliary muscle

Question 16

how does the ciliary muscle react to accommodate for near vision?
-when this happens, what property of the lens allows it to contract into a more spherical shape

Answer 16

ciliary muscle contracts, reducing the tension on the suspensory fibers
its natural elasticity

Question 17

ciliary muscle controlled by what type of nerve fibers

Answer 17

parasympathetic nerve fibers

Question 18

emmetropia

-what is it

Answer 18

naturally occurring condition where the image of an object is focused on the retinal surface

Question 19

what are some refractive abnormalities

Answer 19

hypermetropia
myopia
presbyopia

Question 20

hypermetropia

• another name
• what happens

Answer 20

far-sightedness

focal point falls behind the retinal surface

Question 21

myopia

• another name
• what happens

Answer 21

near-sightedness

falls in front of the retina

Question 22

presbyopia

• what is it
• what is a common external accommodation for this?

Answer 22

loss of lens elasticity noted with age
corrective prescriptions may then include a part of the lens that corrects vision for distance and a part that corrects for near vision = bifocals

Question 23

rods

• excitation threshold level
• used in _____ conditions
• rod acuity is _____

Answer 23

low excitation threshold
used in dim conditions
rod acuity is poor (doesn’t matter, because when light is low, you can’t see small objects anyways)

Question 24

cones

• excitation threshold level
• used in _____ conditions
• acuity is…

Answer 24

high excitation level
used in high light conditions
acuity is high

Question 25

which provide color vision: rods or cones

Answer 25

cones

Question 26

ability to distinguish color vision is due to presence of...

Answer 26

three separate cone populations, each of which is maximally sensitive to a different wavelength of light

Question 27

what are the difference cone populations responsible for color vision?

Answer 27

blue green red

Question 28

color blindness | -results from...

Answer 28

absence of one or more of the cone populations

Question 29

what is the rest of the retina doing that is not responsible for sensing light?

Answer 29

neural coding of visual signals

Question 30

generator potentials - originate... - transmitted to... - altered by...

Answer 30

originate in receptors transmitted to bipolar cells altered by other cells in the retina

Question 31

generator potential pathway can be visualized as... | -what are they?

Answer 31

two separate systems - vertical system - horizontal system

Question 32

how do signals pass in the vertical system?

Answer 32

from receptors to bipolar cells to ganglion cells

Question 33

what happens in the horizontal system?

Answer 33

horizontal and amacrine cells provide lateral interactions (lateral inhibition) between the different vertical system components

Question 34

ganglion cellc | -function

Answer 34

final stage of retinal processing | transmit information to subcortical visual centers in the brain

Question 35

optic nerve is formed by what types of cells

Answer 35

axons of ganglion cells

Question 36

receptive field of a ganglion definition

Answer 36

area in visual space (or the corresponding area of retinal surface) which, upon illumination, influence the signaling of that neuron -remember on-center and off-surround

Question 37

ganglion cells can be categorized on the basis of their...

Answer 37

response duration | morphology

Question 38

"sustained" ganglion cells - characteristic - typically correspond with what size ganglion cells

Answer 38

respond as long as the stimulus remains within the receptive field small ganglion cells (P-cells)

Question 39

"transient" ganglion cells - characteristic - typically correspond with what size ganglion cells

Answer 39

respond only when the light is turned on or off | correspond with large ganglion cells (M-cells)

Question 40

M-cells | -primarily concerned with...

Answer 40

signaling changes in the scene being viewed | -includes movement, changes in light and dark contrast, and basic form analysis

Question 41

P-cells | -primary function

Answer 41

provide information about fine detail (high resolution analysis of image) and color

Question 42

what is a visual field

Answer 42

the part of space that is being viewed

Question 43

signals transmitted through the central visual pathways are divided into...

Answer 43

primary and secondary pathways

Question 44

explain the concept of hemifields within the visual field | -this is accomplished at the level of the...

Answer 44

visual field can be divided by a vertical line at the fixation point into a left and right hemifield each half of the brain receives information only from the opposite (contralateral) hemifield this separation is accomplished at the level of the optic chiasm

Question 45

relation bewteen binocularity and homonymity

Answer 45

images of the visual world are composed of information from the two eyes (binocular) which are merged to form a single image (homonymity)

Question 46

homonymous | -this term, as it applies to visual fields, describes...

Answer 46

both eyes viewing the same or corresponding visual fields

Question 47

which part of the brain is perceiving the contralateral half of the visual field -what is this called?

Answer 47

primary visual cortex | called contralateral homonymous perception

Question 48

everything caudal to the optic chiasm is carrying only...

Answer 48

contralateral homonymous sensation

Question 49

hemianopia - also called... - what is it

Answer 49

also called hemianopsia | loss of visual perception of half of the entire visual field

Question 50

heteronymous | -as it applies to visual fields, what does it describe

Answer 50

describes individual eye viewing different visual fields

Question 51

if each eye is only able to see the ipsilateral temporal visual field and not the nasal visual fields, the deficit would be classified as - give both names - which is preferred

Answer 51

binasal heteronymous hemianopia | binasal hemianopia is preferred