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Neuro Block 3 > Hearing And Balance > Flashcards

Hearing And Balance Flashcards

0
Q

What are the three main components of the temporal bone?

A

Petrous - interior ridge containing the middle ear
Mastoid - auricular muscle attachment, many foramina to allow things to pass through, composed of air cells that can be repositories for infection
Squama Temporalis - thin and transparent, place where the Temporalis muscle attaches

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1
Q

Where are the mechanoreceptors that transducer fluid movements induced by sounds and head movement?

A

The inner ear within the petrous part of the temporal bone

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2
Q

What is a major repository for infections in the temporal bone?

A

The air cells that compose the mastoid of the temporal bone

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3
Q

How is sound intensity measured?

A

In decibels

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4
Q

What is the equation for calculating decibels?

A

dB = 20*log(P/P0)

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5
Q

What is dB SPL?

A

Same reference for all frequencies

Relative to 2x10^-5 N/m2

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6
Q

What Is dB HL (SL)?

A

Relative to the lowest sound pressure detected by individuals

Different reference level for each frequency

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7
Q

What is linearity?

A

What you put in is what you get out

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8
Q

What system is the middle eye?

A

A linear system

If you put in two frequencies you get two out

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9
Q

What type of system is the cochlea?

A

Nonlinear

If you out in two frequencies you get out multiple ones out, the ones different from your input and distortion products

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10
Q

How does (asymmetric) cauliflower ear happen?

A

Shearing to the anterior auricle causes it to separate from the elastic cartilage and tears the blood vessels

The subsequent hematoma stimulate cartilage growth

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11
Q

What are the four sensory nerves to the external ear?

A

Greater auricular (c2,3)
Lesser occipital
Auricular branch of the vagus nerve
Auriculartemporal branch of the mandibular nerve (V3)

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12
Q

Stimulation of what nerve can evoke then vago-vagal reflex resulting in fainting?

A

The auricular branch of the vagus nerve

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13
Q

What nerves innervate the tympanic membrane?

A

Auricular temporal of V (trigeminal)

Auricular branch of X (vagus)

Tympanic branch of IX (Glossopharyngeal)

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14
Q

What does vibration of the tympanic membrane do?

A

Cause the malleus and incus to pivot resulting in the stapes footplate vibration at the oval window

GAIN of pressure results in air conduction being better than bone conduction

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15
Q

Around how many decibels are lost due to conductive hearing loss because of sound reflection?

A

40-55dB

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16
Q

How is energy loss minimized in hearing conduction?

A

By impedance matching by the ossicles and tympanic membrane

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17
Q

What are the three aspects of the middle ear that minimize energy loss of sound?

A
  1. Areal ratio - the area of the tympanic membrane is much larger than the round window
  2. Lever ratio - the length of the malleus arm is greater than the incus arm
  3. Buckling action - force is transmitted from the center of the tympanic membrane
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18
Q

What two properties determine an objects resonant frequency (determined by acoustic impedance)?

A

Mass - heavier objects vibrate at lower frequencies

Stiffness - less elastic objects vibrate at a higher frequency

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19
Q

What structures affect mass and stiffness of the middle ear?

A

Ossicles contribute mass

Volume of the middle ear space affects stiffness

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20
Q

What do you worry about with otitis media?

A

Speech development
Maximal loss of 40-55dB

Low freq sounds like speech are affected first

High freq sounds are not affected until the mass of middle ear bones is increases

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21
Q

How do diseases of the middle ear progress with hearing loss?

A

Low freq (stiffness/space) first

High freq (mass/ossicles) later

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22
Q

What is otosclerosis?

A

Abnormal growth of bone in the middle ear
Results in immobilization of the stapes
Can occur in the cochlea adding sensorineural loss
Common cause of bilateral gradual hearing loss I’m adults
70% hereditary
2x in females
More common in whites
Repaired surgically

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23
Q

Where is the Na rich perilymph?

A

In the bony labyrinth

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24
Q

Where is the K rich endolymph?

A

In the membranous labyrinth

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25
Q

What is contained in the membranous membrane?

A

Receptor hair cells in a gelatinous matrix

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26
Q

Where are the six receptive fields of the inner ear?

A

3 cristae ampullaris. 1 in each semicircular canal

2 maculae ( one in each the saccule and utricle)

1 organ of corti (cochlea)

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27
Q

What is the common histology of the 6 receptive areas?

A

I and II type receptors

Supporting (sustentacular) cells are the hair cells

Gelatinous matrix overlying the hair and supporting cells

Afferent and efferent innervation

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28
Q

What receptors do sensory fibers usually have?

A

Type I hair cells

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29
Q

What receptors do motor fibers usually have?

A

Type II hair cells

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30
Q

Where does CN VIII exit?

A

The cranial vault with CN VII through the internal auditory meatus

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31
Q

What for things does the Vestibularcochlear nerve split into when it is in the auditory meatus?

A
  1. Cochlear nerve to the organ of corti
  2. Superior division of the vestibular nerve to and from the utriclar macula, and the ant. and lat. ampullaris
  3. Inferior division of the vestibular nerve to and from the saccular macula
  4. Nerve to and from the posterior cristae ampullaris
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32
Q

What are the two types of hair cells?

A

Type 1 - true receptors

Type 2 - amplifiers

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33
Q

What is the shape of type 1 hair cells?

A

Pyriform in shape

Have a globular base containing the nucleus

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34
Q

What is the shape of type 2 hair cells?

A

Cylindrical with a centrally located nucleus

35
Q

What is the arrangement of hair cells in the vestibular system?

A

Type 1 and 2 are randomly arranged within receptive regions

36
Q

What is the arrangement of hair cells in the cochlea?

A

Precise

Type 1 are called inner hair cells
Type 2 are called outer hair cells

Based on their position within the organ of corti relative to the modiolus

37
Q

What are the three aspects of hair cell structure that is critical to their function?

A

Both types are mechanoreceptors

Type 1 and 2 have diff afferent and efferent innervation

In the cochlea out hair cells (OHCs) have specialized lateral cisternae and other structural adaptations that support their function as contractile units

38
Q

How many hair cells does 1 afferent nerve supply for type 1 receptors?

A

1 hair cell

39
Q

How many hair cells does 1 afferent nerve supply for type 2 receptors?

A

Many

40
Q

What type of receptor for hair cells do efferents have direct large contact with the OHC somas?

A

Type 2

41
Q

What displacement is depolarizing for hair cell transduction?

A

Toward the tallest row of stereocilia also called positive deflection

In the cochlea this corresponds to movement towards the scala vestibuli

42
Q

What displacement is hyperpolarizing for hair cell transduction?

A

Towards the shortest row of stereocilia

Corresponds to movement towards the scala tympani

43
Q

What are the two components of the vestibular system?

A

Semicircular canals (motion detectors)

Otolith organs (utricle and saccule) (gravity detectors)

44
Q

A lesion to what structure would cause the sensation of spinning?

A

The semicircular canals

45
Q

A lesion to what area would induce the sensation of tilt?

A

The otolith organs (utricle and saccule)

Gravity detectors

46
Q

What is responsible for fixating the visual image on the fovea?

A

The vestibular system

47
Q

What output is integrated with the vestibular system and perceived as the same?

A

Proprioception = perception of body in space

However for others it is used as a reference postural system

48
Q

What way of deflection does stereocilia cause depolarization in the semicircular canal?

A

Horizontal - toward the utricle

Anterior and posterior - away from the utricle

49
Q

How does depolarization occur of the horizontal canals in relation to head movement?

A

The same direction as head movement

Left head turn depolarized the left horizontal canal

50
Q

What is the natural pairing of anterior/posterior canals?

A

Left anterior with right posterior

Right anterior with left posterior

51
Q

How are the anterior and posterior canals related to each other?

A

And 90 degrees

The anterior canal is 41 degrees to the sagital plane

52
Q

What is the preferred angle for stimulation of the

A/P canals?

A

Opposite for the anterior canal on one side and the posterior canal on the other

53
Q

What does tilting your head forward do to your a/p canals?

A

Depolarization of the anterior canals

Hyperpolarization for the posterior canals

Bottom line, for the A/P canals depolarization occurs in the same direction as head movement

54
Q

What are the otolith organs?

A

The saccule and utricle

Detect gravity (linear acceleration)

55
Q

What are otoconia?

A

Small calcium carbonate and protein particles embedded in the overlying gelatinous otolith membrane

They produce drag on the stereocilia when the head changes position

56
Q

What is the orientation of the hair in the utricle and saccule when the body is in anatomical position?

A

The patch of hair cells in the utricle is nearly horizontal, stereocilia are vertical

In the saccule the hair cells are vertical and the stereocilia are horizontal

57
Q

How is directionality conferred in the otolith organs?

A

Solely by the orientation of the hair cell stereocilia

This is opposed to the semicircular canals where the orientation of the canals confers directionality

58
Q

What is the striola?

A

A curved dividing ridge that runs through each macula

59
Q

What is the orientation of the kinocilia in the utricle and saccule?

A

Utricle - kinocilia toward the striola

Saccule - kinocilia away from the striola

In any position some hair cells will be depolarized and others hyper polarized in both otolith organs

60
Q

What is characteristic of rightward nystagmus?

A

Slow movements to the left
Fast movements to the right

(Saccade gaze is fast)
(Pursuit gaze is slow)

61
Q

What is pursuit controlled by?

A

The vestibulo-ocular reflex

62
Q

What is saccade controlled by?

A

High centers like the cortex

63
Q

What is positional alcohol nystagmus?

A

Nystagmus caused by alcohol

64
Q

How does alcohol cause nystagmus?

A

Alcohol changes the relative density of the cupulae and the endolymph

Preferentially entering the cupulae making them less dense than the endolymph

65
Q

When alcohol has entered the cupulae what is caused when the head is lying on its right side?

A

Right beating nystagmus

However when alcohol leaves the cupulae you get the opposite eye nystagmus

66
Q

What is Benign paroxysmal positional vertigo (BPPV)?

A

Age or trauma can cause otoconia to detach from the utricle and log into the semicircular canal (usually posterior)

67
Q

What is the most common cause of vertigo?

A

Benign paroxysmal positional vertigo

68
Q

How is BPPV detected?

A

By the Dix-hallpike maneuver

69
Q

What are some clinical signs of BPPV?

A
  • Patient prefers to lay with the effected ear up
  • Lag period of a few seconds
  • Rolling spin
  • Vertigo is triggered by movement in the opposite direction, nystagmus is reversed
  • rapid onset for 20-30 sec
  • disrupts nearly all life
  • often self resolves
70
Q

What maneuver can return otoconia to the utricle in BPPV?

A

The Epley maneuver

71
Q

What is labyrinthitis?

A 
Inflammation of the inner ear
Usually viral
1-2 weeks after the flu
May cause hearing loss or tinnitus 
No treatment for viral cases
72
Q

What is required for hearing transduction to occur?

A

The basilar membrane to vibrate. Inducing stereocilia deflection in the hair cells

73
Q

What is the directionality of hair cell transduction in hearing?

A

Toward the scala vestibuli is depolarizing

Toward the scala tympani is hyperpolarizing

74
Q

How is sound transmitted from the basilar membrane?

A

Not due to the pressure wave but to the basilar membrane resonating after the pressure wave

Therefore establishment of the traveling wave vibration is independent of how motion is induced in the perilymph

75
Q

What lymph is contained in the scala vestibuli, tympani, and media?

A

Scala vestibuli and tympani is perilymph

Scala media is endolymph

76
Q

How does sounds pressure travel through the cochlea?

A

When sound is delivered to the oval window, it will a send from the base of the scala vestibuli to the apex where it is transferred via the helicotrema to the scala tympani the sound pressure will then travel back down to the round window where it will be relieved

77
Q

What is the bony core of the cochlea?

A

The modiolus

Defines the medial direction in the cochlea

Surrounded by bony spiral lamina

78
Q

What is around the modiolus?

A

The three scalar wrap around it on the spiral lamina

Three times

79
Q

Where do the scala vestibuli and tympani join?

A

At the helicotrema

80
Q

Where is the basilar membrane?

A

In between the scala tympani and media

It supports the organ of corti

81
Q

Where does the auditory nerve run?

A

Through the modiolus

Apical fibers are found In the core of the nerve bundle and basal fibers toward the outside
This preserves the tonotopic relationship

82
Q

What are the three main functional regions around the scala media?

A

Organ of Corti - sensory hair cells that transducer sound into a receptor potential
Spiral ganglion - cell bodies of the sensory neurons that send action potentials to the brain stem
Stria Vascularis - produces endolymph and generates the endocochlear potential

83
Q

Where do nerve fibers to the inner ear become unmyelinated?

A

When they pass through the habenula perforata to reach the hair cells

84
Q

What is the function of the stria Vascularis?

A

Adjacent to the spiral ligament, this is a critical part of K recycling, that moves K into the scala media.

Also generates the endocochlear potential

Neuro Block 3 (17 decks)

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