chapter 5 part2: the visual system Flashcards
what is electromagnetic energy?
fluctuating electrical and magnetic waves
wave length of visible light
400-700nm (ROYGBIV)
how can someone alter their visible spectrum of light?
change their diet drastically
sclera
white in the eye
iris
coloured by pigments
(melanin = brown, lipochrome = yellow brown)
- muscle controls how much light
- equivalent to camera shutter
limbal ring
- darker around eye in youth
- site of stem cells
- border of cornea and sclera
what is the limbal ring also known as?
the limbus
the limbus is a common site for. the occurrence of
corneal epithelial neoplasm
what does the limbus contain?
fribovascular ridges
aka
palisades of Vogt
Pupil
hole through which light enters
closing of pupil
(closing)
in response to light, pupillary reflex
- opens also in response to objects approaching fast
dilation of pupil
(opening)
arousal / sexual
processing complex information (even math)
increases sex appeal
cornea
curved, transparent, bends incoming light, focus incoming visual image to back
what does the cornea cover?
the iris and pupil
where does the lens focus/ bend light onto?
the back of the eye
when the lens is fat, how far is the object?
it is near
when the lens is flat and skinny, how far is the object/
far
Myopia (nearsightedness) affects on cornea, eyes, lens
cornea is too steep
eyes too long
lens focuses image in front of rear of the eye.
Hyperophia (farsighted)
cornea too flat
eye too short
lens does not thicken
Presbyopia
lens loses flexibility
eyeball becomes shorter
this comes with age.
two kinds of photoreceptors
rods and cones
where are rods and cones found in the eye?
outermost layer of the retina.
which are more abundant in the typical human eye, rods or cones?
rods
what are rods insensitive to?
red light
the photoreceptors, rods, are responsible for…..
basic shapes and forms
dark adaptation
peripheral vision (not in fovea)
the photoreceptors, cones, are responsible for….
colour vision
sensitivity to detail
Cones require more light than rods. Which colours are they more sensitive too?
Green, yellow
Where the cones highest in density?
fovea
site of visual transduction
retina
What are light receptor cells comprised of?
bipolar and ganglion cells
bipolar convergence
True or false: some scientists believe that the retina is actually part of the brain.
True, however this is heavily debated.
The fovea is a central part of the …..
the retina.
sharpness, fine detail
photopigments
difference in light perception comes from chemical changes post light exposure
photopigments come from
rhodopsin in rods
what vitamin affects photopigments
vitamin a
what kind of cells is the optic never comprised of?
bundled retinal ganglion cells
point at which the optic nerves cross
optic chiasm
where do most optic nerves go through?
the LGN V1 (cortex) , part of thalamus
some nerves go through superior colliculus
what causes a blind spot in your eye?
this is where your optic nerve is formed (ganglion cells)
trichromatic theory of colour
young and hemoltz
- vision sensitive to 3 primary colours since we have 3 types of cones (blue, green, red)
Colour blindness and the types
- monochromats (no colour)
- dichromats (2 types of cones, only see red and green. Can’t distinguish reds, this is what dog and cats have)
- more common in males because it’s linked to x genes.
opponent processing theory
the theory that afterimage hapens because cones for colour get saturated, give off signal for opposite colour as a result.
hubel and wiesel
- studied cats and similar vision in humans
- mapped V1// found that cells respond best to lines of particular orientations.
v1 cells
- respond to simple features of environment (build perception of visual world)
- simple cells (responds to vertical lines of preferred position)
complex cells
respond to oriented bar over range of positions
- some only respond to oriented bars in motion
feature detection
- use minimal patterns to detect object features
- complex cells do this (detect lines and edges)
- found in temporal lobes/ parietal lobe)
gestalt principles
how we perceive whole objects rather than parts
- governed by 6 main principles
6 main principles of gestalt (kohler and kafka)
proximity - close to eachother looking likea whole
similarity - comprise a whole more than dissimlar
continuity- perceived as whole even if blocked
closure - fill in whats missing when partial info present
figure and ground- focal point against background.
symmetry - whole rather than parts
