Auditory I, II, and III Flashcards Preview

MS2 - Nervous System > Auditory I, II, and III > Flashcards

Flashcards in Auditory I, II, and III Deck (46):
1

Sound pressure level is equal to ___________.

20 x log([pressure]/[pressure reference])

Where P(ref) = 20 micro Pascals

2

We typically lose ________ frequency hearing first.

high

3

The body of the ear (that helps catch and direct sound waves) is called the __________.

pinna

4

The bones of the middle ear, from outside to inside, are ______________.

malleus, incus, and stapes

5

A static pressure difference between the middle ear and the external auditory meatus will lead to what kind of hearing loss?

Conductance

6

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.

7

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).

8

What is the size of the cochlea?

About the size of a chickpea

9

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.

10

There are two ends of the cochlear: the base and the apex. Where does the stapes contact?

The base (at the oval window)

11

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.

12

What happens at the round window when the oval window is pressed?

It presses out – like a release valve

13

The hole at the end of the basilar membrane is the _______________; it connects which two cavities?

helicotrema; scala vestibuli and scala tympani

14

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

15

Perilymph is the fluid in the ______________ (basilar side of hair cells). What is its composition?

scala tympani; low potassium, high sodium

16

The stereocilia are connected by ___________.

tip links

17

The stereocilia of the outer hair cells are embedded in the ___________.

tectorial membrane

18

What diuretic can "completely wipe out" your outer hair cells?

Furosemide – leading to a 60 dB sensorineural hearing loss

19

The outer hair cells function as a __________.

cochlear amplifier

20

Each cochlea contains how many hair cells?

16,000

3,500 inner hair cells
12,500 outer hair cells

21

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)

22

True or false: one inner hair cell can connect to many auditory nerve fibers.

True

23

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!

24

How do hair cells react to stimulation?

They depolarize by the influx of potassium from the unique endolymph.

25

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.

26

The mapping of sounds onto the basilar membrane is called _____________.

tonotopy

27

High frequency hearing is lost first by noise-induced damage to the ____________.

stereociliated cells in the organ of Corti

28

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.

29

What are ITDs and ILDs?

Interaural time differences and interaural level differences

30

Interaural level differences are only used in distinguishing ____________. ITDs are used in distinguishing ____________.

high-frequency sounds; low frequency sounds

31

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

32

Brodmann's areas 44 and 45 are __________.

Broca's area

33

Which part of the brain is Wernicke's area?

posterior temporal lobe (Brodmann 22)

34

Describe otosclerosis.

Arthritic bone growth in the middle ear impedes the movement of the ossicles, resulting in conductive hearing loss

35

Sitting within the ____________ and on top of the ____________ is the organ of corti.

scala media; basilar membrane

36

The oval window bulges (during compression) into the scala ____________.

vestibuli

37

There are three rows of ____________ hair cells and one row of ___________.

outer; inner hair cells

38

There are how many hair cells per cochlea?

16,000

39

A collapse of the endocochlear potential (for potassium) results in _______________.

sensorineural deafness

40

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.

41

From the inferior colliculus, fibers project mainly to the _____________.

ipsilateral medial geniculate

42

The medial geniculate projects fibers to the _____________.

primary auditory cortex (in the superior temporal gyrus)

43

The inferior colliculus brings together auditory impulses from the ____________ side of the body.

contralateral

44

Neurons exhibit phase locking to _________ frequency sounds.

low

45

Spectral cues are only for sounds greater than __________ kHz.

5

46

The "coincidence mismatch" system occurs in the ___________.

medial superior olive

Decks in MS2 - Nervous System Class (111):