Auditory I, II, and III Flashcards
Sound pressure level is equal to ___________.
20 x log([pressure]/[pressure reference])
Where P(ref) = 20 micro Pascals
We typically lose ________ frequency hearing first.
high
The body of the ear (that helps catch and direct sound waves) is called the __________.
pinna
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?
Conductance
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?
Scala vestibuli
Scala media
Scala tympani
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 ___________.
tip links
The stereocilia of the outer hair cells are embedded in the ___________.
tectorial membrane
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 __________.
cochlear amplifier
Each cochlea contains how many hair cells?
16,000
3,500 inner hair cells
12,500 outer hair cells
How many auditory nerve fibers connect to each ear?
30,000
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.
True
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.
