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outer ear consists of

pinna and auditory canal

functions of outer ear

funnels sound, causes eardrum to vibrate

middle ear consists of

tiny bones (ossicles) linking eardrum to oval window

function of middle ear

increase pressure exerted in inner ear

inner ear consists of

cochlea; fluid filled structure

function of inner ear

where transduction takes place

what type of sense is hearing

wave

amplitude determines

loudness

frequency determines

pitch

hair cells

in cochlea, receptor cells for hearing located along basilar membrane

basilar membrane

membrane on the floor of the inner duct of the cochlea

how hearing works

vibration of ossicles against oval window causes waves in basilar membrane, hair cells bend causing impulse and neurotransmitters released by hair cells act upon auditory neurons

basilar membrane characteristic

flexible

tectorial membrane

runs parallel to basilar membrane inside inner duct

eardrum

separates outer ear from inner ear

oval window

membrane at the far end of middle ear, smaller area than tympanic membrane so pressure funneled

where are hair cells located

on the basilar membrane

cilia

tiny hairs that protrude from each hair cell into inner duct and abut against tectorial membrane

tectorial membrane characteristics

less flexible (doesn't move when basilar membrane moves)

conduction deafness

deafness that occurs when ossicles in the middle ear become rigid and cannot carry sounds inward from tympanic membrane to cochlea

what can people with conduction deafness hear?

vibrations that reach cochlea by routes other than middle ear

conventional hearing aid is

a device that magnifies sound pressure sufficiently for vibrations to be conducted by other bones on the face into the cochlea

what helps people with conduction deafness

a conventional hearing aid

sensorineural deafness

deafness resulting from damage to hair cells of cochlea or auditory neurons

cochlear implant is

a device that performs the transduction task normally done by the ear's hair cells by translating sounds into electrical impulses and sending impulses through wires permanently implanted into cochlea where they stimulate terminals of auditory neurons

when can cochlear implant be used

when deafness results from destruction of hair cells, not when auditory nerve has been destroyed

types of deafness

conduction deafness and sensorineural deafness

position in membrane at which wave reaches peak amplitude depends on

frequency of the tone

distance traveled by high frequency waves is

short

distance traveled by low frequency waves is

long

bekesy's hypothesis about hearing

rapid rifing in neurons that come from proximal end of membrane accompanied by little or no firing in neurons from more distal parts is interpreted as high pitched sounds; rapid firing neurons from more distal portion of membrane interpreted as lower pitched sounds

auditory masking

the ability of one sound to mask (prevent hearing of) another sound

asymmetry of auditory masking

low frequency sounds mask high frequency sounds much more easily than high frequency sounds mask low frequency sounds

pattern of hearing loss with age

sensitivity to high frequency lost to a much greater degree than low frequencys with age

why does hearing change with age?

because of wearing out of hair cells with repeated use (coding for high frequencys acted upon by all sounds, low frequency hairs only acted on by low frequency sounds)

for relatively low frequencies, percieved pitch depends on

which part of basilar membrane is maximallhy active and the timing of that activity (ie frequency of action potentials)

auditory sensory neurons send their output where

to nuclei in the brainstem which sends axons to primary auditory area of cerebral cortex

how are neurons in primary auditory cortex organized

tonotopically

tonotopically definition

high-frequency tones activate neurons on one end of cortex, low-frequency tones activate neurons on other end

what determines the general form of hte tonotopic map

heredity

what determines the specific amount of cortex that is devoted to any particular range of frequencies

experience

intraparietal sulcus

area of the parietal lobe of the cortex which receives input from the primary auditory cortex; involved with music perception and visual space perception

sound localization depends on

the time at which each sound wave reaches one ear compared to the other

how are words identified?

from patterns in change of frequency and amplitude that occur over time as the word is spoken

phonemes

individual vowel and consonant sounds that make up words

phonemic restoration

an illusion in which people hear phonemes that have been deleted from words or sentences as if they were still there

what determines which sound is heard in phonemic restoration

the surrounding phonemes and meaningful words and phrases that they produce

how do auditory neurons vary

some have higher thresholds than others; brain uses info about pattern of impulses to perceive loudness; different auditory neurons respond to different differences in time sound received

rods

very sensitive to light, not sensitive to color

cones

not as sensitive to light, involved in color vision

where are rods concentrated

on the periphery of the retina

where are cones concentrated

at the fovea

what are there more of, rods or cones?

more rods (120-125 million) than cones

photoreceptors

specialized light-detecting cells that evolved and became connected to animal's nervous system

retina

membrane lining rear interior of the eyeball; where photoreceptors located

cornea

convex transparent tissue that covers the front of the eyeball

function of cornea

helps focus light that passes through cornea

iris

immediately behind cornea; pigmented doughnut-shaped, provides color of eye

pupil

black-appearing center in the iris; hole through which light can pass into the eyeball

lens

behind the iris, adjustable

function of lens

adds to focusing process begun by cornea

how does lens shape change

becomes more spherical when focusing on objects close to eye, flatter when focusing on those farther away

transduction

process by which a stimulus from the environment generates electrical changes in neurons, done by photoreceptor cells

fovea

pinhead-size area of hte retina that is in teh most direct line of sight, specialized for high visual acuity

acuity

ability to distinguish tiny details

photochemical

a chemical that reacts to light; present on outer segment of each photoreceptor

rhodopsin

the rods' photoreceptor

how many types of cones are there

3

optic nerve

neurons that run from the back of the eye to the brain

blind spot

the place on the retina where the axons of neurons converge to form optic nerve

cone vision

aka bright light vision or photopic vision; specialized for high acuity and color perception

rod vision

aka dim-light vision or scotopic vision; specialized for sensitivity (ability to see in dim light)

dark adaptation

the graduali ncrease in sensitivity that occurs after you enter a darkened room

light adaptation

the more rapid decrease in sensitivity that occurs after you turn on a bright lamp or step out into sunlight

how does bright light make rods nonfunctional

light causes rhodopsin to break down into two inactive substances

bipolar cells

short neurons on which rods and cones form synapses

ganglion cells

longer neurons whose axons leave the eye at the bind spot to form the optic nerve

where do bipolar cells form synapses

on ganglion cells

how does convergence vary between rods and cones

rods have lots of convergence, cones have little or no convergence

place theory

pitch perceived determined by where in cochlea waves reach peak amplitude

pigments

chemicals that absorb some wavelengths and thereby prevent them from being refelcted

subtractive color mizing

the mixing of pigments; pigments create color by subtracting (absorbing) some of the light waves that would otherwise be reflected to the eye

white

no wavelengths of light absorbed, all reflected

black

all wavelengths absorbed, none reflected

additive color mixing

occurs when colored lights are mixed

three primaries law

different wavelengths of light can be used to match any color that the eye can see if they are mixed in the appropriate proportions

primaries

any three wavelengths as long as one is from the long-wave end of spectrum, one from short-wave end, and one from middle

law of complementarity

pairs of wavelengths can be found that, when added together, produce the visual sensation of white

saturated colors

colors produced by a single wavelength

unsaturated

colors that come more and more to resemble white

standard chromaticity diagram

can be used to determine color that will result from mixing three standard primaries and which pairs of wavelengths are complimentary

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