06c: Peripheral Auditory System Flashcards
Perceived loudness of sound reflects (X).
X = amplitude of pressure fluctuations
The Sound Pressure Level (SPL) is defined as:
20*log(P/Po)
SPL has which units?
dB
If the pressure of a sound wave is 100 times greater than reference level, the intensity would have which value?
SPL = 20*log(100) = 40 dB
For every increase in pressure by one order of magnitude, the intensity we perceive is increased by:
20 dB
Perceived pitch of sound reflects (X).
X = frequency
Frequency units.
Hz
Explain reason for “impedance mismatch” in (X) system?
X = auditory;
Air is less dense than inner ear fluid, so most E from incoming sound wave would be reflected back upon reaching interface
The (X) system overcomes “impedance mismatch” because (Y) is (Z) times greater than:
X = auditory; Y = ear drum/tympanic membrane Z = 20
Oval window/footplate of Stapes
Since the tympanic membrane’s surface area is so much larger than (X), the (Y) is amplified correspondingly.
X = oval window Y = force per unit area
The orientation and movement of middle ossicles bones provides (X) advantage factor of (Y).
X = mechanical; Y = 1.5
T/F: sound arriving at inner ear through the skull passes the middle ear.
False
Ossicles are present in (external/middle/internal) ear. List them, from lateral to medial.
Middle
- Malleus
- Incus
- Stapes
(X) is the site for transducing sound waves into neural impulses
X = cochlea
Cochlea composed of (X) number of (perpendicular/parallel) canals. List them, from top to bottom.
X = 3
Parallel;
- Scala vestibuli
- Scala media
- Scala tympani
Which canals in cochlea contain perilymph, which is high in (X) ion?
Scala vestibuli and tympani
X = Na
Which canals in cochlea contain endolymph, which is high in (X) ion?
Scala media
X = K
Which canals in cochlea in contact with round window?
Scala tympani
Which canals in cochlea in contact with oval window?
Scala vestibuli
(Round/oval) window found at base of cochlea.
Both
Reissner’s membrane separates:
Scala vestibuli from scala media
Basilar membrane separates:
Scala media from scala tympani
Name the structure at (base/apex) of cochlea that connects (X) and (Y) canals.
Apex;
X = scala vestibuli
Y = scala tympani
Helicotrema
(X) is the name of the sensory epithelium of the auditory system. It sits on top of (Y).
X = organ of corti Y = basilar membrane
Base of HCs in auditory system are implanted in (X). Tips protrude into (Y).
X = organ of corti Y = tectorial membrane
HCs in auditory system composed of:
Stereocilia only
Auditory system: depolarization when stereocilia bend toward (X).
X = tallest stereocilia
(X) membrane in inner ear is the one that vibrates in response to sound waves.
X = basilar
Stereocilia of HCs in auditory system are bathing in (peri/endo)lymph of (X) canal, which is (high/low) in K and has standing potential of (Y).
Endolymph;
X = scala media
High;
Y = +100 mV
Sound intensity is encoded in which way(s)?
- Firing rate
2. Number of HCs (and afferent fibers) responding
Sound pitch is encoded in which way(s)?
Location of basilar membrane that is vibrating (between apex and base)
Sound with high (X) will vibrate (apex/base) of (Y) membrane.
X = frequency;
Base;
Y = basilar
Resonator theory is that which describes how (X) is encoded.
X = sound pitch/frequency
Each auditory afferent nerve has a preferred (X) that it’s most sensitive to.
X = sound frequency
As a sound deviates further from an auditory nerve’s preferred frequency, there’s an (increase/decrease) in (X) at which the nerve can detect the sound.
Increase;
X = threshold of loudness (dB)
Auditory nerve fibers have a (more/less/equally) selective response to frequency of sound compared to the basilar membrane.
More selective (second filter)
“Second filter” tuning mechanism in auditory nerve fibers may be due to which phenomena?
- Lateral inhibition
2. Mechanical and electrical resonance
(X) ion entering and depolarizing auditory hair cell from (perilymph/endolymph) is due to (chemical/electrical) gradient.
X = K
Endolymph; electrical
(X) ion leaving and repolarizing hair cell goes into (perilymph/endolymph) due to (chemical/electrical) gradient.
X = K
Perilymph;
Chemical
When HC is depolarized, due primarily to (X) ion (leaving/entering), which other key ion (leaves/enters) HC and helps in repolarization process.
X = K
Entering;
Ca enters
“Ringing” or electrical resonance in hair cells is dependent on which factor(s)?
- Density of K and Ca channels in hair cell
2. Kinetics of calcium-gated K channels
HC toward apex of membrane will have (higher/lower) density of K/Ca channels with (faster/slower) calcium-gated K channels.
Lower; slower
(Inner/outer) HCs provide most, (X)%, of input to auditory nerve.
Inner;
X = over 95
(Inner/outer) HCs change shape to mechanically (dampen/amplify) (X).
Outer;
Amplify;
X = oscillatory movement of basilar membrane
In tinnitus, there’s uncontrolled (X) of (Y), producing an actual measurable sound emitted by tympanic membrane.
X = cyclical contraction Y = outer HCs
