5 - Vision Flashcards
What does wavelength show
colour
short wavelength: violet, blue
longer wavelength: red, orange
What does amplitude show
brightness
high amplitude: very bright
low amplitude: dim
What does purity show
saturation
high purity/completely saturated: vibrant colours
low purity/desaturated: dull colours
Describe the visual pathway of the eye ball
- cornea
- pupil
- lens
- vitreous humor
- retina
What does the iris do
controls the amount of light that enters the eye
What does the pupil do
allows light through
low light: large pupil (dilate)
lots of light: small pupil (constrict)
What does the cornea do
focuses light
transparent, curved outermost region
What does the lens do
final “fine-tuning” focusing
What does the sclera do
white region covered by a tough membrane
What is the vitreous humor
clear jelly like substnace in main chamber of the eye
What is the retina
neural tissue
What is accomodatino
when the lens changes shape
close focus: rounder lens
far focus: elongated lens
Describe the cells/layers that light goes through in the retina
- ganglia cells
- relays signal to the brain - bipolar cells and amacrine cells
- processes signal further and passes on to - photoreceptor layer
- detext light and pass info to the next layer
Describe the photoreceptor cells
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
What is the retinal pigment epithelium
rpe
provides nutrients to photoreceptors
what are horizantal and amacrine cells
allow cells in the retina to communicate to each other
some amount of visual processing done in retina before signal sent to the brain
What is the blind spot
optic disc
area where optic nerves exit the retina
no photoreceptors there
brain makes up what we’re missing
where is there a smaller and more precise receptive filed
center of retina (fovea)
Where is there a larger and coarser receptive field
in the periphery of retina
What are the streams of the primary visual cortex (V1)
ventral stream: “what” pathway
- colour and form
- temporal lobe
dorsal stream: “where” pathway
- depth and motion
- parietal lobe
What is topographic organization
neighbouring regions in the retina correspond to neighbouring regions in the visual cortex
which cells combine into which cells
photoreceptors –> ganglion cells –> LGN cells –> visual cortext cells (V1 cells)
Describe the evolution of the eye
- light sensitive patch –> presence or absence of light
- curved “cup” eye –> direction of light
- pinhole eye –> can resolve detail of image by changing light in the eye
- crude lens –> lens and cornea and spherical shape –> relatively solid, shape changes very little
- adjustable lens –> flexible and allows for accommodation –> can focus at varying distances
What is cumulative selection
an evolutionary process whereby new adaptations are layered upon old adaptations
What are the factors affecting variance across species
- geographic location
- where their food comes from
- movement, shape and colour of prey
What are the eye types
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)
What are the functions of the eye
Which eye shape increases the functions
- resolution: acuity
- clarity and sharpness - sensitivity: ability to get enough light
- spotting a far star at night (night vision)
bigger eyes = increase acuity and sensitivity
Hoe do human/hawk eyes differ from cat/horse/owl eyes and deep sea animal eyes
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
What are laterally directed eyes
wide total view
2 separate fields of view
poor depth perception
- prey animals continually scan environment for predators
What are front-facing eyes
predators
narrow total view
essentially single field view
excellent depth percetion
TF vision is the most developped system in fetuses
False
- a lot of additional work that has to be done b/f fully functional
What happens at the second prenatal month
eyes formed
what happens at the 6th prenatal month
fetus reacts to light
random firing of retinal cells
Describe the eyes of a newborn
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)
Describe the eye at 3 months
almost adult-like focusing
Describe the eye at 11 years
visual brain area development complete
When is visual acuity fully developed
1 year
