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ORL > Basics of the auditory & vestibular system > Flashcards

Basics of the auditory & vestibular system Flashcards

1
Q

vestibular: ________
________: hearing

A

vestibular: balance
auditory: hearing

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2
Q

True or false: the vestibular system is at the forefront of our conscious experience.

A

False: it’s the auditory system. We only consciously notice the vestibular system when something goes wrong.

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3
Q

Functions of the vestibular system (3)

A

1) Generating muscle contractions that will put our body where we want it to be
2) Reorienting the body when something pushes us aside (vestibulospinal reflexes)
3) Moving our eyes continually to keep visual world fixed on our retinas even though our head may be nodding about (vestibuloocular reflexes)

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4
Q

Hearing allows us to do three things:

A

Detect, localize, and identify the nature of things

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5
Q

Which has a true kinocilium: vestibular or auditory hair cells?

A

Vestibular hair cells! Auditory hair cells lose there kinocilium with maturity

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6
Q

Bulbous basal area, surrounded by calyx-shaped afferent nerve terminal

A. inner hair cells
B. Type II vestibular hair cells
C. outer hair cells
D. Type I vestibular hair cells

A

D.
Type II - cylindrical; bouton-shaped afferent nerve terminals
Inner and outer hair cells - auditory

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7
Q

How many stereovilli in both vestibular and auditory hair cells?

A

50-150

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8
Q

Where does the stereovilli connect?

A

Cuticular plate

“Put the stereo on the cute plate.”

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9
Q

Characteristic of a true cilia?

Which is the true cilia: kinocilium or stereocilia?

A

9 + 2 pattern

True: kinocilium

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10
Q

The CSF is low in K+ and high in Na+. Is perilymph the same? Y/N

What is the resting potential of perilymph?

A

Y: Perilymph is on the basolateral side of hair cells with a resting potential of 40 mV.

PeLowKey (Pillow key/pi-lowkey) - Perilymph, low K+

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11
Q

Which bathes the stereovilli: endolymph or perilymph?

A

Endolymph - high K+ (150 mM), low Na+ (1 mM)

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12
Q

Which is the force that tends to drive K+ into the channels at the tips of the vestibular hair cells and across the apical membrane? Chemical or electrical gradient?

A

Electrical gradient - ~40 mV

Driving force for K+ influx is even higher in the auditory system

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13
Q

Appropriate stimulus for a hair cell; leads to influx of K+ and depolarization

A

Bending of stereocillia towards kinocilium

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14
Q

Causes depolarizing receptor potential

a) hair bundle moves towards longer stereovilli
b) hair bundle moves perpendicular to preferred direction
c) hair bundle moves away from longer stereovilli
d) sensitivity of hair bundles

A

A is the answer
B - not so responsive, hair cells are selective about direction they bend towards
C - hyperpolarizing
D - tiny movements needed for a response

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15
Q

__ nm (large atom diameter) gives detectable response while ~ __ nm (diameter of 1 stereovillus) is when the response is saturated for hair cells

A

0.5, 150

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16
Q 
Spring-like molecular linkage describes the movement of:
A) stereovilli and kinocilium
B) channel gating
C) stereovilli and channel gating
D) receptor potentials
A

C - d/t tip links

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17
Q

Cadherins that form tip links?

A

Cadherin 23 & protocadherin 15

Note: exposure to low Ca^2+ solution destroys tip links => abolish transduction

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18
Q

Mechanosensitive channels at the basolateral side, mechanoinsensitive channels at the stereovilli tips: true or false?

A

False. It should be vice versa.

Side note: steady leak of depolarizing K+ at rest allows hair cells to respond to positive and negative deflections of its stereovilli

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19
Q

T/F: Voltage-gated Ca^2+ channels are found in the presynaptic side and are somewhat active at rest.

A

True! Found in the vestibular hair cells and inner hair cells. Most active during mechanically-induced depolarization of hair cell.

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20
Q

Neurotransmitters released when Ca^2+ enters the hair cell: (Hint: they -ATE and left no crumbs)

A

Glutamate & aspartate

Note: greater transmitter release means greater rate of action potential firing in postsynaptic axon

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21
Q

For mammals, all hair cells are contained in the ____ labyrinth.

A

membranous labyrinth - bilateral set of interconnected tubes & chambers

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22
Q

Function of vestibular dark cells of the otolithic and semicircular canals?
A) secret Ca^2+ that enter the hair cells
B) secret K+ and responsible for the high K+ in endolymph
C) release glutamate and aspartate
D) NOTA

A

B! Mechanism of secretion similar to stria vascularis of auditory system

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23
Q 
Function of the macula:
A) detect linear acceleration
B) detect head tilt
C) A & B
D) NOTA
A

C! Remember HUVS

24
Q

The reversal line divides the macula into 2 regions. Sacule: kinocilia point ______ reversal line; utricle: kinocilia point _____ reversal line

A

Saccule: away from (SAWay)
Utricle: towards (go TOWARDS the kUTe)

25
Q

____ increases the density of the otolithic membrane in the macula vs. the surrounding endolymph.

A

Otoconia/otolits.

26
Q

Primary sensory axon for macula? (hint: branch of CNVIII)

A

vestibular nerve

27
Q

Cluster of hair cells: ____ for utricles & saccules, ____ for semicircularis canals

Where cilia is embedded: ___ for utricles & saccules, ___ for semicircularis canals

A

macula, crista ampularis, otolithic membrane, cupula

Note: cupula does not have otoconia unlike the otolithic membrane

28
Q

Three semicircular canals:

Anterior - __ degrees
Posterior - ___
Lateral - ___

A

~41, ~56, ~25

29
Q

Speed of sound?

A

330-340 m/s

30
Q

1) Absolute sound is measured in __

2) Intensities of audible sounds are expressed ___

A

1) pascals (Pa)

2) decibel sound pressure levels (dBSPL)

31
Q 
Used clinically to determine hearing thresholds using the pure-tone audiogram:
A) absolute sound
B) sound intensities
C) Phon scale
D) pure tone
A

D) pure tone (of a single frequency)

32
Q

Sound with identical dBSPL but perceived as having different loudness depending on frequency

A

Phon scale

Note: human ear is most sensitive to sounds around 1000-1500Hz

33
Q

Parts of the outer ear that focus sound waves into the EAC

A

Pinna and tragus

34
Q 
Parts of the external ear are for the localizatin of sound in the:
A) horizontal plane
B) vertical plane
C) sagittal plane
D) linear acceleration
A

B) vertical plane

35
Q

Which is/are true of the eustachian tube?
A) connects the middle ear to the nasopharynx
B) allows otitis media to happen when throat infections or epithelial inflammation is present
C) allows equalizing of air pressure on both sides of the tympanic membrane
D) AOTA

A

D) AOTA

36
Q

The three ossicles that transfer TM vibrations to oval window

A

malleus (ms: tensor tympani), incus, stapes (ms: stapedius)

Note: mentioned muscles dampen sound (protective reflex when ambient sound levels are high)

37
Q

Identification:

1) ____ is the tendency of each medium to oppose movement brought about by pressure waves
2) ____ has 10000 higher (1) than air
3) The ear’s ___ device is the ___ear

A

1) acoustic impedance
2) water
3) impedance-matching; middle

38
Q

(Hint: ossicles)

Lever system that amplifies the pressure of the wave

A

Malleus & incus

Note: System allows conservation of energy. Most energy gets transferred to middle ear.

39
Q 
Lined with fibrocytes, filled with perilymph, and communicate through the helicotrema
A) scala tympani and scale media
B) scala media and scala vestibuli
C) scala vestibuli and scala tympani
D) cochlear aqueduct and scala media
A

C is correct
Scala media is filled with endolymph
Cochlear aqueduct - communication between cochlear perilymph and CSF

Note: sensory organ is the organ of Corti

40
Q

Upper boundary of the scala media is the ___ membrane while the lower boundary is the ___ membrane.

A

Ressner’s membrane, basilar membrane

41
Q 
Auditory endolymph has voltage of +80 mV relative to the perilymph
A) endocochlear potential
B) electrochemical potential
C) endolymph potential
D) electrogradient
A

A) endocochlear potential

  • highest transepithelial voltage in the body
  • main driving force for sensory transduction
  • Loss of this potential is a frequent cause of hearing loss
42
Q

Stria vascularis: secretes K+ into the scala media

1) separate endolymph in the scala media fro the intra-strial compartment: ___
2) separate intra-strial compartment from interstitial fluid of the spiral ligament: ___
3) Important for generation of endocochlear potential: ___

A

1) marginal cells
2) basal cells
3) gap junctions

43
Q

Channels that maintain the high K+ in intermediate cells (stria vascularis)

A

KCNJ10K+ channel - generates the endocochlear potential

KCNQ1 K+ channel- in marginal cells which remove K+ from intrastrial fluid & move it to endolymph

44
Q

Organ of Corti

1) T/F: 1 row of 3500 inner hair cells & 3 rows of 16000 outer hair cells
2) Outer hair cells: ___; inner hair cells: release neurotransmitters
3) T/F: hyperpolarization contracts prestin -> inner hair cells contract
4) 2 reasons why electromotility of outer hair cells is important

A

1) T
2) cochlear amplifier - amplify basilar membrane movement, contracts d/t prestin
NTs released: glutamate
3) F: depolarization contracts prestin -> outer hair cells contract - ELECTROMOTILITY: electrical to mechanical transduction
4) for sensitive hearing & ability to discriminate frequencies

45
Q

Short clicks create an “echo” referred to as ___. The source is the prestin-mediated cochlear amplifier.

A

otoacoustic emission

46
Q

1) T/F: Pitch is subjective
2) Young humans can hear frequencies from __ to _____ Hz
3) Perception of speech: __ to _____ Hz
4) Causes pain: ____ dBPSL
5) T/F: 20 dBPSL whispering, 65 dBPSL normal convo, 90 dBPSL loud traffic, 120 dBPSL train horn

A

1) T
2) ~20 to 20,000 Hz
3) 60 to 12,000
4) >120
5) 20, 60, 80, 120

47
Q 
Increase in the sound amplitude increases the rate of action potentials -> brain interprets as "louder"
A) place coding
B) rate coding
C) amplitude coding
D) blue code
A

B!

48
Q

PLACE CODING

Low frequencies: ____; high frequencies: _____

A

low: apex/helicotrema
high: base (near round and oval windows)

Place coding - Frequency of sound determines where along the cochlea the cochlear membranes vibrate the most and, by extension, which hair cells are stimulated

49
Q

T/F: The basal end of the basilar membrane is wider, floppier, and vibrates at low frequencies.

A

False. It’s the apical end!

50
Q

Where does the enhancement of tuning occur: cochlea or CNS?

A

Cochlea!

Note: without the cochlear amplifier, our ears wouldn’t be sensitive enough to pick up any sound.

51
Q

Maximum passive displacement (w/o cochlear amplifier): __

A

0.1 nm

52
Q 
Effect of electromotility:
A) amplify & sharpen peak of sound-induced wave
B) amplify only
C) dampen sound-induced wave
D) increase frequency of sound
A

A

53
Q 
In which part of the brain is auditory stimuli analyzed?
A) medial geniculate
B) cingulate gyrus
C) medulla & auditory cortex
D) medial geniculate & auditory cortex
A

D!

54
Q

Stimulation of these efferent fibers suppress response of the cochlea to sound (hint: olives)

Main neurotransmitter: _____

A

Olivocochlear efferent fibers - suppress electromotility of outer hair cells

Main NT: Acetylcholine

Note: could provide auditory focus in noisy environments

55
Q

1) Most common cause of human deafness?
2) T/F cochlear implants can be used as long as the auditory nerve is still intact
3) Best candidates of cochlear implants? (2)

A

1) damage to cochlear hair cells
2) T
3) Young children (optimally as young as 1 y.o.), older children (& adults) whose deafness was acquired
after they learned some speech

ORL (2 decks)

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