Flashcards in Auditory I, II, and III Deck (46):
Sound pressure level is equal to ___________.
20 x log([pressure]/[pressure reference])
Where P(ref) = 20 micro Pascals
We typically lose ________ frequency hearing first.
The body of the ear (that helps catch and direct sound waves) is called the __________.
The bones of the middle ear, from outside to inside, are ______________.
malleus, incus, and stapes
A static pressure difference between the middle ear and the external auditory meatus will lead to what kind of hearing loss?
Roughly 99.9% of the acoustic energy from sound is deflected by the ear. Why?
Sound "does not like" to pass from air to water due to impedance mismatch, and thus most sound ricochets off.
How is the initial attenuation of sound energy overcome?
The tympanic membrane is a fluid-filled sac with a surface area of 60 mm^2. It narrows to a point on the malleus that is 3 mm^2, thus amplifying the pressure (because pressure = force / area).
What is the size of the cochlea?
About the size of a chickpea
What are the three chambers of the cochlea?
Though it's easier to think of just the vestibuli and the tympani separated by the basilar membrane.
There are two ends of the cochlear: the base and the apex. Where does the stapes contact?
The base (at the oval window)
Describe the changes in the basilar membrane from base to apex.
The base – where the stapes vibrates – is narrower and tighter and conducts higher frequencies, while the apex is wider and "floppier" and conducts lower frequencies.
What happens at the round window when the oval window is pressed?
It presses out – like a release valve
The hole at the end of the basilar membrane is the _______________; it connects which two cavities?
helicotrema; scala vestibuli and scala tympani
Endolymph is the fluid in the ____________ (apical side of hair cells). What is its composition? What structure mediates this?
scala media; high potassium, low sodium; stria vasularis
Perilymph is the fluid in the ______________ (basilar side of hair cells). What is its composition?
scala tympani; low potassium, high sodium
The stereocilia are connected by ___________.
The stereocilia of the outer hair cells are embedded in the ___________.
What diuretic can "completely wipe out" your outer hair cells?
Furosemide – leading to a 60 dB sensorineural hearing loss
The outer hair cells function as a __________.
Each cochlea contains how many hair cells?
3,500 inner hair cells
12,500 outer hair cells
How many auditory nerve fibers connect to each ear?
Type I: 28,500 (connect to inner)
Type II: 1,500 (connect to outer)
True or false: one inner hair cell can connect to many auditory nerve fibers.
Type II nerve fibers connect to how many outer hair cells?
Lots! There are only 1,500 type II fibers, yet there are 12,500 outer hair cells!
How do hair cells react to stimulation?
They depolarize by the influx of potassium from the unique endolymph.
True or false: the area immediately surrounding the ossicles is fluid-filled.
False. This area is air-filled – which is which changes in air pressure lead to conductance loss.
The mapping of sounds onto the basilar membrane is called _____________.
High frequency hearing is lost first by noise-induced damage to the ____________.
stereociliated cells in the organ of Corti
What physical exam sign suggests conductive hearing loss?
The patient can hear the sound of a struck tuning fork better when pressed to their mastoid process (as compared to through air). Sensorineural hearing loss would present as the opposite.
What are ITDs and ILDs?
Interaural time differences and interaural level differences
Interaural level differences are only used in distinguishing ____________. ITDs are used in distinguishing ____________.
high-frequency sounds; low frequency sounds
The primary auditory cortex and secondary auditory cortex are which Brodmann areas?
41 and 42 – both of which are in the posterior section of the lateral fissure
Brodmann's areas 44 and 45 are __________.
Which part of the brain is Wernicke's area?
posterior temporal lobe (Brodmann 22)
Arthritic bone growth in the middle ear impedes the movement of the ossicles, resulting in conductive hearing loss
Sitting within the ____________ and on top of the ____________ is the organ of corti.
scala media; basilar membrane
The oval window bulges (during compression) into the scala ____________.
There are three rows of ____________ hair cells and one row of ___________.
outer; inner hair cells
There are how many hair cells per cochlea?
A collapse of the endocochlear potential (for potassium) results in _______________.
True or false: unilateral lesions to the auditory tracts rostral to the mid pons produce unilateral deafness.
False. Some axons branch bilaterally in the mid pons (after the superior olivary nucleus), so unilateral lesions will not lead to unilateral deafness.
From the inferior colliculus, fibers project mainly to the _____________.
ipsilateral medial geniculate
The medial geniculate projects fibers to the _____________.
primary auditory cortex (in the superior temporal gyrus)
The inferior colliculus brings together auditory impulses from the ____________ side of the body.
Neurons exhibit phase locking to _________ frequency sounds.
Spectral cues are only for sounds greater than __________ kHz.