eye Flashcards
(35 cards)
anatomy of the eye
Light enters through pupil
Passes through lens
Lens inverts and reverses image
Lense focuses light
Light strikes photoreceptors (rods and cones) in the retina
Optic nerve carries stimulus to brain
the FOVEA
a diver in the back of the eye.
two cell layers- ganglion and bipolar cells
cones are directly stimulated
no blood vessles in front of these receptors
GOOD FOR WHAT YOU ARE FOCUSED ON. peripherial everything is blurry. CONTAINS ALL CONES, NO RODS.
Ganglion cells axons from the optic nerve which sends impulses out of eye.
RECEPTIVE FIELDS
Each ganglion cell responds to light from a specific area of the visual field
Receptive fields have an “ON” area and “OFF” area
When light strikes the “ON” area, that ganglion cell fires faster (excitation)
When light strikes the “OFF” area, that ganglion cell fires slower (inhibition)
Allows for precise location of light source
WHAT IS COLOR
To humans, color is the brain’s interpretation of electromagnetic radiation with wavelengths between 400 and 700 nanometers. Other animals are capable of perceiving shorter (UV) or longer (infrared) wavelengths.
TWO THEORIES OF COLOR VISION
Trichromatic Theory
Opponent Process Theory
TRICHROMATIC THEORY
we have three sets of rods, suggests that different shades result from relative rates of activity from three different cones.
short- blue
medium- green
long- red
Respond maximally to a specific wavelength.
At cone layer. Back region!
negative afterimage
if you stare at one color long enough, then take it away, you will see the opposite color.
White will activate all cells so we perceive the opposite color because the first cells are tired.
OPPONENT PROCESS THEORY
PAIRED OPPOSITES (opposition to colors opposing each other)
we perceive color in terms of paired opposites (red v green, yellow v blue, black v white)
excitation of bipolar cell, where they converge.
one bipolar cell produces one color, whereas the inhibition of the same cell produces the opposite color.
At bipolar/ ganglion level of retina.
Explains negative afterimage.
NEGATIVE AFTERIMAGE
After prolonged increase/decrease in firing, a ganglion cell undergoes an opposing “rebound effect”
White light activates all cone types equally
Ganglion cells that were previously inhibited fire faster than normal
Opposite color is perceived
3 TYPES OF COLOR BLINDNESS
Monochromatism
Dichromatism
Achromatopsia
Monochromatism
Only one cone type
True color blindness
Only see shades of light and dark
born with this type of cone
Dichromatism
4 TYPES
two types of cones, but cant perceive certain colors.
*Protanopia – lack L (red) cone
*Deuteranopia – Lack M (green) cone
*
Protanopes & deuteranopes
confuse red & green
*Tritanopia – Lack S (blue) cone
Sees only reds and greens
Confuse yellows, grays, blues
Not as common
Achromatopsia
Cortical color blindness
TWO TYPES OF DISORDERS
VISUAL AGNOSIA
MOTION BLINDNESS
VISUAL AGNOSIA
Can see and detect movement, but cannot identify objects by sight
Can identify objects by touch
Damage to “what” pathway
Agnosia Video
MOTION BLINDNESS
Difficulty judging distance of moving objects and speed of movement
Damage to “where” pathway
ACOUSTIC ENERGY
BOUNCES OFF SURFACES/ CAN BE ABSORBED
VIBRATIONS
CAUSE MOLECULES TO CONDENSE/RAREFY (PULL APART) AND TRAVEL AWAY FROM OBJECT (HAIR RECEPTORS IN INNER EAR ARE STIMULATED)
3 types of stimulus
pitch
loudness
timbre
pitch
FREQUENCY of air molecules condensing and compressing
measured in (Hz) Hertz
must be at least 30-20,000Hz to hear
loudness
INTENSITY of a sound
Timbre
“color of music”/ complexity of a sound.
a sound may have the same pitch and loudness, but you can tell the difference because the timbre differs. ex: piano and sax playing at the same time.
vision
how we interpret the environment around us.
our brain interprets the world based on stimuli from our environment, based on sensory organs
how vision works
light is directed into the pupil, the muscle bands around detect the amount of light allowing to enter. (when your eyes dilate it lets in more light, such as at night)
image will be flipped upside down and focused on back of retina, on the FOVEA.
ganglion cells send axons out optic nerve
crosses at optic chasm then sent to occipital
