5 - Vision

Question 1

What does wavelength show

Answer 1

colour

short wavelength: violet, blue

longer wavelength: red, orange

Question 2

What does amplitude show

Answer 2

brightness

high amplitude: very bright
low amplitude: dim

Question 3

What does purity show

Answer 3

saturation

high purity/completely saturated: vibrant colours
low purity/desaturated: dull colours

Question 4

Describe the visual pathway of the eye ball

Answer 4

1. cornea
2. pupil
3. lens
4. vitreous humor
5. retina

Question 5

What does the iris do

Answer 5

controls the amount of light that enters the eye

Question 6

What does the pupil do

Answer 6

allows light through

low light: large pupil (dilate)
lots of light: small pupil (constrict)

Question 7

What does the cornea do

Answer 7

focuses light

transparent, curved outermost region

Question 8

What does the lens do

Answer 8

final “fine-tuning” focusing

Question 9

What does the sclera do

Answer 9

white region covered by a tough membrane

Question 10

What is the vitreous humor

Answer 10

clear jelly like substnace in main chamber of the eye

Question 11

What is the retina

Answer 11

neural tissue

Question 12

What is accomodatino

Answer 12

when the lens changes shape

close focus: rounder lens
far focus: elongated lens

Question 13

Describe the cells/layers that light goes through in the retina

Answer 13

3. ganglia cells
   - relays signal to the brain
4. bipolar cells and amacrine cells
   - processes signal further and passes on to
5. photoreceptor layer
   - detext light and pass info to the next layer

Question 14

Describe the photoreceptor cells

Answer 14

rods
- low light vision (b/c contains rhodopsin)
- 125 million
- night vision
- poor visual acuity
- concentrated in periphery
- no colour

cones
- high light vision (b/c contains iodopsin)
- 6 million
- day vision
- good visual acuity
- concentrated in fovea
- colour
- smaller receptive fields

Question 15

What is the retinal pigment epithelium

Answer 15

rpe
provides nutrients to photoreceptors

Question 16

what are horizantal and amacrine cells

Answer 16

allow cells in the retina to communicate to each other

some amount of visual processing done in retina before signal sent to the brain

Question 17

What is the blind spot

Answer 17

optic disc

area where optic nerves exit the retina

no photoreceptors there

brain makes up what we’re missing

Question 18

where is there a smaller and more precise receptive filed

Answer 18

center of retina (fovea)

Question 19

Where is there a larger and coarser receptive field

Answer 19

in the periphery of retina

Question 20

What are the streams of the primary visual cortex (V1)

Answer 20

ventral stream: “what” pathway
- colour and form
- temporal lobe

dorsal stream: “where” pathway
- depth and motion
- parietal lobe

Question 21

What is topographic organization

Answer 21

neighbouring regions in the retina correspond to neighbouring regions in the visual cortex

Question 22

which cells combine into which cells

Answer 22

photoreceptors –> ganglion cells –> LGN cells –> visual cortext cells (V1 cells)

Question 23

Describe the evolution of the eye

Answer 23

1. light sensitive patch –> presence or absence of light
2. curved “cup” eye –> direction of light
3. pinhole eye –> can resolve detail of image by changing light in the eye
4. crude lens –> lens and cornea and spherical shape –> relatively solid, shape changes very little
5. adjustable lens –> flexible and allows for accommodation –> can focus at varying distances

Question 24

What is cumulative selection

Answer 24

an evolutionary process whereby new adaptations are layered upon old adaptations

Question 25

What are the factors affecting variance across species

Answer 25

- geographic location - where their food comes from - movement, shape and colour of prey

Question 26

What are the eye types

Answer 26

simple eyes - eyeball, lens, retina * crude lens and accommodating lens compound eyes - detect movement at close distances - retina, lens and ommatidium (each point in a slightly different direction to gather the light that lays directly in front of it)

Question 27

What are the functions of the eye Which eye shape increases the functions

Answer 27

1. resolution: acuity - clarity and sharpness 2. sensitivity: ability to get enough light - spotting a far star at night (night vision) bigger eyes = increase acuity and sensitivity

Question 28

Hoe do human/hawk eyes differ from cat/horse/owl eyes and deep sea animal eyes

Answer 28

humans/hawks: - acuity = excellent - low-light vision = poor cat/horse/owl: - acuity = poor - low-light vision = excellent deep sea animals: - acuity = excellent - low-light vision = excellent

Question 29

What are laterally directed eyes

Answer 29

wide total view 2 separate fields of view poor depth perception - prey animals continually scan environment for predators

Question 30

What are front-facing eyes

Answer 30

predators narrow total view essentially single field view excellent depth percetion

Question 31

TF vision is the most developped system in fetuses

Answer 31

False - a lot of additional work that has to be done b/f fully functional

Question 32

What happens at the second prenatal month

Answer 32

eyes formed

Question 33

what happens at the 6th prenatal month

Answer 33

fetus reacts to light random firing of retinal cells

Question 34

Describe the eyes of a newborn

Answer 34

weak lens muscle (limits how well they can focus) inconsistent pupil rxn (can't react properly to changes in light --> blurry images) low cell density cells are immature (especially fovea --> matures at 4 years)

Question 35

Describe the eye at 3 months

Answer 35

almost adult-like focusing

Question 36

Describe the eye at 11 years

Answer 36

visual brain area development complete

Question 37

When is visual acuity fully developed

Answer 37

1 year