2-2 auditory system Flashcards by elise beckman

functions of pinna

funnelilng of sound

sound localization / differentiating sounds

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functions of ear canal

protects the ear drum from foreign bodies

amplifies certain frequencies

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functions of middle ear

transmits sound to the cochlea

pressure equalizer

amplification of sound

impedance matching

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tympanic membrane

middle ear

transmission & amplification

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ossicular chain

middle ear

malleus, incus, stapes

impedance matching
sound transmission to cochlea

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oval window

middle ear

transmission of sound waves

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round window

middle ear

pressure release valve for cochlear fluids

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eustachian tube

pressure equalizer of middle ear

needs to be diagonal in order to drain
horizontal in children

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middle ear muscles

middle ear

tensor tympani, stapedius

acoustic reflex
protects inner ear from loud noises

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functions of inner ear

hearing & balance

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tonotopic organization of cochlea

apex = lower frequencies

base = higher frequencies

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scala vestibuli

uppermost chamber of cochlea

filled w/ perilymph

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scala media

middle chamber of cochlea

filled w/ endolymph

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scala tympani

bottom chamber of cochlea

filled w/ perilymph

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perilymph

low K+
high Na+

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endolymph

high K+
low Na+

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organ of corti

located in the scala media

rests on top of basilar membrane

includes stereocilia (hair cells)

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organ of corti function

converting mechanical vibrations or sound waves into electrical signals

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basilar membrane

tonotopic organization

frequency depends on stiffness & mass of an object

becomes bigger in diameter as it goes toward apex

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mass dominant bm

apex end

BM is wider, more flexible, greater mass

lower frequenvies

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stiffness dominant bm

basal end

bm narrower, stiffer, lower mass

higher frequencies

outer hair cells

straight, thin, 3 rows

send info to the brain through bm as it vibrates

actin present - can change its length

efferent = 85-85%
afferent = 5-15%

inner hair cells

curved, thick, single row

determine which frequencies are present

sensory - sending more specific info to brain

afferent = 85-90%
efferent = 5-15%

are hair cells polarized or nonpolarized

highly polarized

excess of negative or positive charged ions outside of cell

1. mechanoelectrical transduction

sound waves cause the stereocilia to move opening of MET channels in IHC membrane

2. receptor potential

the opening of transduction channels allows positively charged ions (K+) to enter the hair cell

3. neurotransmitter release

in inner hair cells, the receptor potential triggers the release of neurotransmitters at the synapses w/ auditory nerve fibers

4. action potential

the release of neurotransmitters at the synapses between inner hair cells & auditory nerve fibers initiates action potentials in the nerve fibers

summary of cochlear events - air mechanisms

stapes pushes on oval window perilymph moves in the scala vestibuli

summary of cochlear events - fluid mechanisms

fluid pushes on the round window endolymph moves in the scala media OHCs move basilar membrane moves

summary of cochlear events - electrical & chemical mechanisms

ion channels in IHCs open neurotransmitters released auditory nerve (AN) fibers get stimulated

info coded by cochlea

frequency intensity timing

frequency

pitch of sound how often nerve is firing

intensity

energy carried by the sound how many neurons are firing

timing

when the firing is occurring

firing rate

of action potentials or electrical impulses generated by a neuron over a period of time of spikes / second

firing rate threshold

level at which the firing rate is greater than the spontaneous rate

frequency encoding - place theory

frequency info from which AN fibers are firing where they came from on the basilar membrane

frequency encoding - temporal theory

freq info form timing of neural firing higher freq - the neuron will skip stimulus cycles groups of neurons compensate for missing spikes

CANS

central auditory nervous system

cochlear nucleus

CANS 1st synapse from the brainstem

superior olivary complex

CANS inputs from both ears converge

inferior colliculus

CANS integration & routing of signals, pitch discrimination

lateral lemniscus

CANS carries info about sound from the cochlear nucleus to various brainstem nuclei

medial geniculate body

further specialization can detect more specific features

auditory cortex

further specialization assists w/ plasticity

interaural time difference

crucial cue using tome to differentiate between the left & right ear low frequencies

ineraural level difference

crucial cue using intensity to differentiate between the left & right ear

spectral cues

provide info about the direction of a sound source, especially in vertical plane

neural plasticity

the ability of the nervous system to change its activity in response to intrinsic or extrinsic stimuli by reorganizing its structure, functions, or connections

wernickes area

superior temporal gyrus language processing & production