2-2 auditory system Flashcards
functions of pinna
funnelilng of sound
sound localization / differentiating sounds
functions of ear canal
protects the ear drum from foreign bodies
amplifies certain frequencies
functions of middle ear
transmits sound to the cochlea
pressure equalizer
amplification of sound
impedance matching
tympanic membrane
middle ear
transmission & amplification
ossicular chain
middle ear
malleus, incus, stapes
impedance matching
sound transmission to cochlea
oval window
middle ear
transmission of sound waves
round window
middle ear
pressure release valve for cochlear fluids
eustachian tube
pressure equalizer of middle ear
needs to be diagonal in order to drain
horizontal in children
middle ear muscles
middle ear
tensor tympani, stapedius
acoustic reflex
protects inner ear from loud noises
functions of inner ear
hearing & balance
tonotopic organization of cochlea
apex = lower frequencies
base = higher frequencies
scala vestibuli
uppermost chamber of cochlea
filled w/ perilymph
scala media
middle chamber of cochlea
filled w/ endolymph
scala tympani
bottom chamber of cochlea
filled w/ perilymph
perilymph
low K+
high Na+
endolymph
high K+
low Na+
organ of corti
located in the scala media
rests on top of basilar membrane
includes stereocilia (hair cells)
organ of corti function
converting mechanical vibrations or sound waves into electrical signals
basilar membrane
tonotopic organization
frequency depends on stiffness & mass of an object
becomes bigger in diameter as it goes toward apex
mass dominant bm
apex end
BM is wider, more flexible, greater mass
lower frequenvies
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
- mechanoelectrical transduction
sound waves cause the stereocilia to move
opening of MET channels in IHC membrane
- receptor potential
the opening of transduction channels allows positively charged ions (K+) to enter the hair cell
- neurotransmitter release
in inner hair cells, the receptor potential triggers the release of neurotransmitters at the synapses w/ auditory nerve fibers
- 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
