audition Flashcards
why do we have a middle ear?***
to increase the pressure of ear to get the water molecules moving at equal level as the sound changes in the air
as the stapes move in due _______ in fluid pressure the basilar membrane bulges _________
increase in fluid pressure, the basilar membrane bulges down
high frequency stimulates what part of the cochlea?
the base because it’s the most stiff area
low frequency stimulates what part of the cochlea?
the apex and thus it moves from apex to base and moves along the entire basilar membrane
the trajectory of sound travel is affected by?
the frequency of the sound NOT the increase in sound pressure
for the frequency of a sound on a particular hair cell if the match of frequency is supplied by the stimulus then the displacement required is at a __________ because you give a matching frequency. but if you depart from that matching frequency you must __________ the sound pressure level to cause a just threshold response.
at a minimum
must increase the sound pressure
sound is
frequency
perception of sound is
pitch
change in air pressure is
an auditory stimulus
what is the biggest cause of deafness
hair cell death
what does the amplitude of a sound wave represent?
the magnitude of pressure change , the greater the amplitude the greater the physical magnitude of sound
which part of the ear is filled with an aqueous medium?
the inner ear
a 40 dB change means what in terms of the amount that sound must be increased to hear it?
must be increased by 100 fold to hear it and i.e. it is significant hearing loss
is the force at the oval window the same as the force applied to the tympanic membrane?
no oval window force exceeds tympanic membrane force by 1.3 x
what is tympanometry?
a clinical technique that measures the impedance of he middle ear.
what is impedance?
convert low pressure, high displacement vibrations into high pressure of the air into, low displacement vibrations suitable for driving cochlear fluids
the middle ear transfers the incoming vibration from the comparatively large, low impedance tympanic membrane to the much smaller, high impedance oval window.
how does tympanometry work?
a microphone is placed in the ear and the amount of sound that is absorbed through the middle ear or is reflected from the middle ear is measured at the microphone
what is the normal value in tympanometry? and what could a value above that indicate?
3 dB, > that could indicate wax build up or otitis media ( middle ear infection)
bone and soft tissue have an impedance close to ______. therefore w/o a tympanic membrane or middle ear ossicles, sound can be transmitted through bones and soft tissue of the head to the ________
water
cochlea
the analysis of different frequencies depends on the way different frequencies affect a membrane in the cochlea called the
basilar membrane
there is more deflection at which end of the basilar membrane?
the apex ( think of bending a long stick or a short stick )
each frequency of sound has a max deflection and then?
dissipates really quickly in the basilar membrane
the character of the traveling of the wave is reflected in the :
pattern of discharges transmitted by the primary auditory neurons
auditory receptors arranged in an orderly manner along the basilar membrane are stimulated how and by what?
stimulated mechanically by the displacements of the traveling wave
how can you increase the excitation of any auditory nerve fiber by?
presenting a sound wave frequency with a peak traveling wave displacement nearer the position of that fiber’s receptor cell
what can you say about the character of the peak displacement traveling wave?
it is very narrow only the width of a few hair cells
the organ corti houses the?
auditory receptors
the organ corti rests upon the
basilar membrane
displacement of the basilar membrane will cause
movement of the auditory cell receptors
the basiar membrne operates relative to the what membrane
tectorial membrane
pushing the basilar membrane and the tectorial membrane up will
put a shearing force on the cilia in one direction while pushing them down will place a shearing force in the opposite direction
what happens when cilia are sheared in a certain direction
the hair cells depolarize and the discharge rate of the neuron increases over it’s spontaneous level.
how does the length of the hair cells at the apex compare to that of the those at the base?
the ones at the apex are more than twice as long as the ones at the base.
what is the role of the central auditory system?
to interpret the discharge patterns of auditory nerve fibers in order to produce the perception of sound
how many cochlear nuclei are there?
3
full range of frequencies transduced by the cochlea is represented in each of the 3 nuclei in what manner?
higher frequencies are represented dorsally and low frequencies are represented ventrally in each nucleus
in the primary auditory cortex how is the sound organized?
high frequency is more rostral and low frequency is more caudal
Is the auditory cortex involved in pitch?
not involved in pitch per se but is involved in the analysis of PATTERNS OF PITCH ( i.e. a series of different frequencies)
