06c: Peripheral Auditory System

Question 1

Perceived loudness of sound reflects (X).

Answer 1

X = amplitude of pressure fluctuations

Question 2

The Sound Pressure Level (SPL) is defined as:

Answer 2

20*log(P/Po)

Question 3

SPL has which units?

Answer 3

dB

Question 4

If the pressure of a sound wave is 100 times greater than reference level, the intensity would have which value?

Answer 4

SPL = 20*log(100) = 40 dB

Question 5

For every increase in pressure by one order of magnitude, the intensity we perceive is increased by:

Answer 5

20 dB

Question 6

Perceived pitch of sound reflects (X).

Answer 6

X = frequency

Question 7

Frequency units.

Answer 7

Hz

Question 8

Explain reason for “impedance mismatch” in (X) system?

Answer 8

X = auditory;

Air is less dense than inner ear fluid, so most E from incoming sound wave would be reflected back upon reaching interface

Question 9

The (X) system overcomes “impedance mismatch” because (Y) is (Z) times greater than:

Answer 9

X = auditory;
Y = ear drum/tympanic membrane
Z = 20

Oval window/footplate of Stapes

Question 10

Since the tympanic membrane’s surface area is so much larger than (X), the (Y) is amplified correspondingly.

Answer 10

X = oval window
Y = force per unit area

Question 11

The orientation and movement of middle ossicles bones provides (X) advantage factor of (Y).

Answer 11

X = mechanical;
Y = 1.5

Question 12

T/F: sound arriving at inner ear through the skull passes the middle ear.

Answer 12

False

Question 13

Ossicles are present in (external/middle/internal) ear. List them, from lateral to medial.

Answer 13

Middle

1. Malleus
2. Incus
3. Stapes

Question 14

(X) is the site for transducing sound waves into neural impulses

Answer 14

X = cochlea

Question 15

Cochlea composed of (X) number of (perpendicular/parallel) canals. List them, from top to bottom.

Answer 15

X = 3
Parallel;

1. Scala vestibuli
2. Scala media
3. Scala tympani

Question 16

Which canals in cochlea contain perilymph, which is high in (X) ion?

Answer 16

Scala vestibuli and tympani

X = Na

Question 17

Which canals in cochlea contain endolymph, which is high in (X) ion?

Answer 17

Scala media

X = K

Question 18

Which canals in cochlea in contact with round window?

Answer 18

Scala tympani

Question 19

Which canals in cochlea in contact with oval window?

Answer 19

Scala vestibuli

Question 20

(Round/oval) window found at base of cochlea.

Answer 20

Both

Question 21

Reissner’s membrane separates:

Answer 21

Scala vestibuli from scala media

Question 22

Basilar membrane separates:

Answer 22

Scala media from scala tympani

Question 23

Name the structure at (base/apex) of cochlea that connects (X) and (Y) canals.

Answer 23

Apex;
X = scala vestibuli
Y = scala tympani

Helicotrema

Question 24

(X) is the name of the sensory epithelium of the auditory system. It sits on top of (Y).

Answer 24

X = organ of corti
Y = basilar membrane

Question 25

Base of HCs in auditory system are implanted in (X). Tips protrude into (Y).

Answer 25

``` X = organ of corti Y = tectorial membrane ```

Question 26

HCs in auditory system composed of:

Answer 26

Stereocilia only

Question 27

Auditory system: depolarization when stereocilia bend toward (X).

Answer 27

X = tallest stereocilia

Question 28

(X) membrane in inner ear is the one that vibrates in response to sound waves.

Answer 28

X = basilar

Question 29

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).

Answer 29

Endolymph; X = scala media High; Y = +100 mV

Question 30

Sound intensity is encoded in which way(s)?

Answer 30

1. Firing rate | 2. Number of HCs (and afferent fibers) responding

Question 31

Sound pitch is encoded in which way(s)?

Answer 31

Location of basilar membrane that is vibrating (between apex and base)

Question 32

Sound with high (X) will vibrate (apex/base) of (Y) membrane.

Answer 32

X = frequency; Base; Y = basilar

Question 33

Resonator theory is that which describes how (X) is encoded.

Answer 33

X = sound pitch/frequency

Question 34

Each auditory afferent nerve has a preferred (X) that it's most sensitive to.

Answer 34

X = sound frequency

Question 35

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.

Answer 35

Increase; | X = threshold of loudness (dB)

Question 36

Auditory nerve fibers have a (more/less/equally) selective response to frequency of sound compared to the basilar membrane.

Answer 36

More selective (second filter)

Question 37

"Second filter" tuning mechanism in auditory nerve fibers may be due to which phenomena?

Answer 37

1. Lateral inhibition | 2. Mechanical and electrical resonance

Question 38

(X) ion entering and depolarizing auditory hair cell from (perilymph/endolymph) is due to (chemical/electrical) gradient.

Answer 38

X = K | Endolymph; electrical

Question 39

(X) ion leaving and repolarizing hair cell goes into (perilymph/endolymph) due to (chemical/electrical) gradient.

Answer 39

X = K Perilymph; Chemical

Question 40

When HC is depolarized, due primarily to (X) ion (leaving/entering), which other key ion (leaves/enters) HC and helps in repolarization process.

Answer 40

X = K Entering; Ca enters

Question 41

"Ringing" or electrical resonance in hair cells is dependent on which factor(s)?

Answer 41

1. Density of K and Ca channels in hair cell | 2. Kinetics of calcium-gated K channels

Question 42

HC toward apex of membrane will have (higher/lower) density of K/Ca channels with (faster/slower) calcium-gated K channels.

Answer 42

Lower; slower

Question 43

(Inner/outer) HCs provide most, (X)%, of input to auditory nerve.

Answer 43

Inner; | X = over 95

Question 44

(Inner/outer) HCs change shape to mechanically (dampen/amplify) (X).

Answer 44

Outer; Amplify; X = oscillatory movement of basilar membrane

Question 45

In tinnitus, there's uncontrolled (X) of (Y), producing an actual measurable sound emitted by tympanic membrane.

Answer 45

``` X = cyclical contraction Y = outer HCs ```