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Neuro B3 - WLB > Week 3 - Fitzakerely (Hearing & Balance) > Flashcards

Week 3 - Fitzakerely (Hearing & Balance) Flashcards

1
Q

As the Semicircular Canals are “motion detectors”, what does a lesion induce the sensation of?

A

Spinning

(Detect head rotation –> angular acceleration)

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2
Q

As the Otolith Organs (utricle and saccule) are “gravity detectors”, what does a lesion induce the sensation of?

A

Tilting

(Detect gravity –> linear acceleration)

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3
Q

What system acts as the postural signal reference?

A

Vestibular system

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4
Q

Where are hair cells found in the semicircular canals?

A

surface of the ampullary crest

(piece of bone that protrudes into the ampulla)

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5
Q

What is the gelatinous matrix that the stereocilia of type I & II vestibular hair cells are embedded in called?

A

Cupula

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6
Q

How are all of the sterociliary bundles in the ampulla oriented?

A

In the same direction!

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7
Q

What pair of semicircular canals are tested in the caloric test?

A

Horizontal canals

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8
Q

What pair of semicircular canals are tested in the Dix-Hallpike test?

A

one pair of anterior/posterior canals

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9
Q

What happens in the semicircular canals when you tilt your head forward (what depolarizes/hyperpolarizes)?

A

Depolarization of Anterior Canals

&

Hyperpolarization of Posterior Canals

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10
Q

What happens in the semicircular canals when you tilt your head forward (what depolarizes/hyperpolarizes)?

A

Depolarization in the Left Horizontal Canal

&

Hyperpolarization in the Right Horizontal Canal

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11
Q

What is labyrinthitis? What are common symptoms?

A

Inflammation of the inner ear

  • Symptoms:
    • vertigo
    • temporary hearing loss
    • tinnitus
    • N/V
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12
Q

Where are the cell bodies of the primary afferent fibers of the central auditory pathway?

A

Spiral Ganglia

&

Vestibular Nerve (Scarpa’s) Ganglia

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13
Q

What are the 6 steps in the Auditory Pathway?

A
  1. Hair cells –> Auditory Nerve
  2. Cochlear Nuclei –> Trapezoid body
  3. Superior Olivary Complex –> Lateral Lemniscus
  4. Inferior Colliculus –> brachium of IC
  5. Medial Geniculate Nucleus –> Internal Capsule
  6. Primary Auditory Nucleus (superior temporal gyrus)
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14
Q

What projections are bilateral in the Auditory Pathway?

A

All central projections, starting with the trapezoid body.

(Cochlear nucleus projects both ipsilaterally and contralaterally)

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15
Q

What are the two important reflex loops from the superior olivary complex?

A
  • Back to the cochlear hair cells - allows loud sounds to modify the vibration of the basilar membrane
    • OHC - efferent synapses on cell body
    • IHC - efferent synapses on afferent fibers
  • Acoustic Reflex - negative feedback loop to the middle ear muscles
    • Trigeminal Motor Nucleus –> Tensor Tympani via CN V3
    • Facial Motor Nucleus –> Stapedius via CN VII
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16
Q

What are the 4 steps of the Vestibular Pathway that is the afferent pathway for perception?

A
  1. Hair Cells (SC/Otolith) –> Vestibular Nerve
  2. Superior/Lateral Vestibular Nuclei –> medial lemniscus
  3. Ventroposterior Nucleus –> Internal Capsule
  4. Vestibular Cortex (debated location)
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17
Q

What are the 4 steps of the Vestibular Pathway responsible for control of head/neck/upper limb position in response to movement?

A
  • Hair cells (Semicircular Canals & Otolith organs)
    • Vestibular Ganglion/Nerve
  • Lateral/Medial/Inferior Vestibular Nuclei
  • Vestibulospinal Reflexes
    • Lateral Vestibulospinal Tract (LVST)
    • Medial Vestibulospinal Tract (MVST)
  • Limb & Trunk (via LVST) OR Upper Back & Neck (via MVST)
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18
Q

What are the four steps of the Vestibular Pathway that are responsible for control of eye position relative to head position (VOR)?

A
  • Hair Cells (Semicircular Canals & Otolith Organs)
    • Vestibular Nerve/Ganglion
  • Superior/Medial Vestibular Nuclei
    • Medial Longitudinal Fasciculus (MILF)
  • Oculomotor Nucleus/Abducens Nucleus/Trochlear Nucleus
    • Superior, medial, and inferior rectus via CN III
    • Lateral Rectus via CN VI
    • Superior Oblique via CN IV
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19
Q

What is the purpose of the Vestibulospinal reflexes?

A

maintaining the head in an upright position

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20
Q

What is the purpose of the Lateral Vestibulospinal system?

A

Compensate for tilts and movements of the body during postural changes

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21
Q

What is the purpose of the Medial Vestibulospinal system?

A

Stabilize head position while walking

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22
Q

In sound localization processing, does the lateral or medial superior olive interpret whether a sound is louder in one ear?

A

Lateral Superior Olive

(high frequencies –> “Intensity Pathway”)

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23
Q

In sound localization processing, does the lateral or medial superior olive interpret whether a sound reaches one ear first?

A

Medial Superior Olive

(low frequencies –> “Time Pathway”)

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24
Q

What is the only way to have an ipsilateral hearing loss?

A

Peripheral lesion

(Cochlea, Auditory Nerve, or Cochlear Nucleus)

25
Q

What type(s) of deficiencies constitute a Central Auditory Processing Disorder (CAPD)?

A
  • Deficiency in:
    • Sound localization & lateralization
    • Discrimination
    • Pattern recognition
    • Temporal aspects of sounds
    • Ability to deal with degraded and competing acoustic signals
      • “Cocktail Party Effect”
26
Q

What type of hearing loss does amplification help combat?

A

Sensorineural

27
Q

In classic posterior canal BPPV, what type of nystagmus indicates that the posterior canal is affected?

A

Upbeating nystagmus

(more rare = downbeating –> anterior canal)

28
Q

In a normal ear, the middle ear pressure equals the atmospheric air pressure due to the function of what?

A

Eustachian tube

29
Q

What is the purpose of the Rinne Test?

A

determination of conductive hearing loss

(tuning fork on mastoid process)

***Due to the amplification provided by the middle ear, in a normal person: air threshold is less than bone threshold (louder through air vs. bone)

30
Q

What is the purpose of the Weber Test?

A

Determination of a conductive vs. a sensorineural hearing loss.

(base of tuning fork placed on top of head)

*Normal = equally lound in both ears

**Conductive = louder in affected ear

***Sensorineural = louder in the normal ear

31
Q

What are common causes of conductive hearing loss?

A
  • ruptured eardrum
  • intratympanic fluid –> otitis media
  • otosclerosis
32
Q

What does a normal audiogram look like?

A

Air conduction = Bone conduction

both thresholds are about 0 Hz

33
Q

What does an audiogram of conductive hearing loss look like?

A

Increased threshold in air conduction:

about 50 dB loss

Conduction block increases the mass (high frequencies) or the stiffness (low frequencies) or both.

*Stiffness (low frequencies) usually affected 1st.

34
Q

What does an audiogram of sensorineural hearing loss look like?

A

Increase in thresholds and/or loss of ability to transduce specific frequencies due to damage to the cochlea, auditory nerve, or cochlear nucleus.

  • Affects both air and bone conducted stimuli.
  • Both air/bone curves exhibit a threshold shift in the affected frequency range.
35
Q

What are common causes of sensorineural hearing loss?

A
  • Noise (hair cell/stereocilia damage)
  • Genetic defects
  • Ototoxic drugs (aminoglycoside antibiotics)
    • gentamicin
    • amikacin
  • Loop diuretics
    • furosemide
36
Q

What fluid does the bony (osseous) labyrinth contain?

A

Na+ rich PERILYMPH

37
Q

What fluid does the membranous labyrinth contain?

A

K+ rich ENDOLYMPH

38
Q

What area of the osseous labyrinth contains the oval and round windows?

A

Vestibule

39
Q

What canals extend from the vestibule?

A
  • 3 semicircular canals
  • Cochlea
  • Vestibular aqueduct
  • Cochlear aqueduct
40
Q

What happens in a rupture of the bony layrinth?

A

Causes CSF flow through the cochlear aqueduct –> Perilymphatic Fistula

(no membranous labyrinth in the cochlear aqueduct)

41
Q

What does it mean that the membranous labyrinth is completely enclosed?

A

There are NO connections between the spaces containing endolymph and those containing perilymph.

42
Q
A
43
Q

What are the four main components of the Membranous Labyrinth?

A
  • Cochlear duct (= scala media)
  • Saccule
    • connected to the cochlear duct via ductus reuniens
  • Utricle
    • connected to the saccula via endolymphatic duct
  • Semicircular canals
44
Q

What are the 6 areas within the inner ear that contain the sensory receptor hair cells?

A
  • 3 cristae ampullaris
    • 1 in each semicircular canal
  • 2 maculae
    • 1 in the saccule
    • 1 in the utricle
  • 1 organ of corti
    • in the cochlea
45
Q

What is the innervation of the inner ear?

A
  • Vestibulocochlear Nerve (CN VIII)
    • Sensory afferents from hair cells (Type I) –> brainstem
    • Brainstem –> Motor efferents to hair cells (Type II)
46
Q

How does the Vestibulocochlear Nerve (CN VIII) exit the cranial vault?

A

Through the internal auditory meatus.

(exits with Facial Nerve CN VII)

47
Q

What are the four branches of the Vestibulocochlear Nerve (CN VIII)?

A
  1. Auditory (cochlea)
  2. Superior Division (utricle, Anterior & Lateral SC)
  3. Inferior Division (saccule)
  4. Posterior Division (Posterior SC)
48
Q

What compartment of the cochlea do vibrations ascend to the apex?

A

Scala Vestibuli

49
Q

What compartment of the cochlea do vibrations descend to the base of the cochlea?

A

Scala Tympani

50
Q

What membrane is the Organ of Corti located on?

A

Basillar membrane

51
Q

In a comatose patient what part of the VOR is present and absent?

A

Present: Pursuit (brainstem)

Absent: Saccade (cortex)

52
Q

In a patient that is brain dead, what part of the VOR will be present and absent?

A

BOTH the PURSUIT and SACCADE will be ABSENT.

53
Q

What produces the endolymph and the endocochlear potential?

A

Stria Vascularis

(contains many of the same ion transporters as the kidney, that’s why drugs that affect renal function are often ototoxic!)

54
Q

What part of the cochlea are high frequencies transduced?

A

Base

55
Q

What part of the cochlea are low frequencies transduced?

A

Apex

56
Q

What determines the absolute threshold of hearing at each frequency?

A

The Middle Ear

57
Q

What are the components of the 3 neuron arc in the Vestibulo-ocular Reflex (VOR)?

A
  1. Hair cell/Vestibular Nerve (CN VIII)
  2. Vestibular Nuclei
  3. Cranial Nerve Motor Nuclei
58
Q

What causes vibration at the oval window?

A
  1. Vibration of the tympanic membrane
  2. Malleus and Incus pivot
  3. Stapes footplate vibrates oval window
59
Q

What produces cerumen in order to protect the tympanic membrane?

A

Large modified APOCRINE GLANDS deep in the dermis of thee external auditory meatus

Neuro B3 - WLB (11 decks)

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