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Module 4: Neuro > Vestibular System II > Flashcards

Vestibular System II Flashcards

1
Q

What are the parts of the tympanic membrane?

A

Two parts, each bordered by the external acoustic meatus and teh tympanic cavity

1. Pars Tensa:
- Three layers:
Skin
Collagen fibers
Mucosa

2. Pars Flaccida
- Two layers:
Skin
Mucosa

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2
Q

What causes conductive hearing loss?

A

Perforation of the tympanic membrane or occlusion of the middle ear (often by ear wax)

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3
Q

What are the symptoms of conductive hearing loss?

A

Sound stimulus is not transmitted to the inner ear, therefore, patients present with:

  • Hearing loss in affected ear
  • Conductive sounds appear louder in affected ear
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4
Q

What are the parts of the middle ear?

A
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5
Q

What are possible complications of otitis media?

A

Temporal lobe abcess

Sigmoid sinus thrombosis

Mastoiditis (in mastoid air cells)

Facial Palsy

Labyrinthintis

Meningitis

ICA Thrombosis

IJV Thrombosis

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6
Q

What is the purpose of the receptors in the inner ear?

A

Respond to movements of the head

For audition

They are mechanoreceptors in specialized epithelium

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7
Q

What are the structures of the inner ear?

A
  1. Bony Labyrinth
  • Semicircular Canals
    (Anterior/Superior, Posterior, Lateral)
  • Vestibule
  • Cochlea
  1. Membranous Labyrinth
  • Filled with Endolymph
  • Contains sensory receptors
  • 4 parts
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8
Q

What is the function of the endolymphatic duct and sac?

A

Reabsorption of endolymph

  • Only part of the inner ear, membranous labyrinth not covered in specialized epithelium
  • Sac is extraosseous part and is positioned by sigmoid sinus to reabsorb endolymph and release it into blood stream
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9
Q

What is Meniere’s Disease?

A

Too much endolymph

Symptoms:

  • Vestibular:
    Dizziness/vertigo
  • Cochlear:
    hearing loss
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10
Q

Where is the crista ampularis and what is its function?

A

Found in the ampulla of semicircular canals, fixed, while the endolymph in the canals is able to move.

  • Contains:
    Sensory Hair cells (2 types)
    Supporting cells
    Cupula

Function is to detect angular movement

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11
Q

What are the 2 types of Hair cells?

A
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12
Q

How does the crista ampularis detect movements of the head?

A

Movement of stereocillia and kinocillium towards cilium leads to depolarization

Movement of stereocillia and kinocillium away from cilium leads to hyperpolarization

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13
Q

Where is the macula found and what is its function?

A

Found in the utricle and saccule, the macule is used to detect Gravity and Linear acceleration

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14
Q

What are otoconia made of?

A

Calcium carbonate

(they are Ca-carbonate crystals)

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15
Q

What is the modiolus?

A

Found in the inner ear, it is a spiral shaped axis of the cochlea

  • made of spongy bone, the cochlea turns approx 2.5x around it
  • Spiral ganglion resides here
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16
Q

What is found in the cochlea?

A

Modiolus

Scala vestibuli (filled with perilymph)

Cochlear duct (filled with endolymph)

Scala tympani (filled with perilymph)

Organ of corti resides on the boundary between cochlear duct and scala tympani

17
Q

What is the organ of corti? What is it made of?

A

Found in the cochlear duct, it is a sound receptor containing:

Inner hair cells - few in #
Outer hair cells - many in #
Supporting Pillar cells (Inner and outer)
Phalangeal cells
Tectorial membrane

base of basilar membrane = high frequencies
apex of basilar membrane = low frequencies

18
Q

What is the shape of a “pure tone”?

A

Sinusoidal sound pressure wave of equal states of compression and rarefaction

–> localized pressure disturbances propagate away from sound source

19
Q

How is a decibel calculated?

A
20
Q

What is the process of hearing?

A
  • Capture mechanical energy from the air (External ear)
  • Conduct sound to receptors (Middle ear)
  • Change mechanical vibrations into action potential firing patterns in an afferent nerve (Inner ear)
  • Transmit neural signal to auditory centers of brain (Ascending auditory pathway)
  • Perceive sound (cerebral cortex)
21
Q

What are sound parameters?

A

Loudness - related to amplitude

Pitch - related to frequency

Timbre - related to shape of waveform

Location

22
Q

What affects detection threshold of sound pressure?

A
23
Q

Why are the ossicles of the middle ear necessary?

A
24
Q

How does attenuation of ossicle movement occur?

Why is this important?

A

Muscles of the middle ear (tensor tympani and stapedius) contract in response to loud noises (>80dB) being most sensitive to lower frequencies

Response latency is too slow to protect from impulsive sounds

Purpose is to most likely reduce noise during vocalization

25
Q

What is the process of cochlear nerve activation in the organ of corti?

A

Sound waves move the basilar membrane of the cochlea

–> tectorial membrane is more stiff and doesn’t move, causeing sheer forces on kinocilia and stereocilia

–> Increased NT released from hair cells

–> Increased AP firing in cochlear nerve afferent fibers occurs

26
Q

What is the Place Theory?

A

The theory that frequency tuning of basilar membranes leads to spatial separation of auditory signal based on frequency (tonotopic organization)

Example:

A 10kHz sound causes max displacement near the base of the helicotrema, while a 0.5kHz sound causes max displacement near the apex
–> these signals remain separated throughout the auditory pathway

27
Q

When does the Place Theory break down?

A

Place Theory doesn’t work at the low end of audible frequency range

–> The frequency map of basilar membrane ends at about 200Hz at Apex of the membrane

28
Q

What is the function of the Stria Vascularis?

A

To produce endolymph

–> epithelium with blood vessels in it found in the cochlear duct

29
Q

What is tinnitus?

A

ringing in the ears

30
Q

What is conductive hearing loss?

What are the test results that identify it?

A

Defects in conductive mechanisms in external or middle ear

  • Weber’s test of conductie hearing (tuning fork on forehead): sound lateralized to bad ear
  • Rhinne test (tuning fork applied to mastoid process then in front of ear): sound is louder on mastoid process
31
Q

What is Sensorineural hearing loss?

What are the test results that identify it?

A

Damage to cochlea, cochlear nerve, or cochlear nuclei

Weber’s test (tuning fork placed on forehead): sound lateralized to good ear

Rhinne test (tuning fork on mastoid process then in front of ear): sound is louder by air conduction, but more energy is needed to hear the sound

32
Q

What are causes of Conductive hearing loss?

A

otosclerosis

middle ear infection

perforation of tympanic membrane

33
Q

What are some causes of sensorineural hearing loss?

A

Meniere’s disease (build up of endolymph)

Noise trauma

Inner ear infection

Drug treatments

Age

Acoustic neuroma

34
Q

What is audiometry?

A

testing of hearing loss by detecting threshold of hearing for specific sound frequencies

–> detection threshold is compared to normal threshold for each frequency to determine if hearing loss exists

35
Q

What is an audiogram?

A

plots of hearing loss (difference between subject’s detection threshold and “normal” threshold) as a function of frequency

  • determined by audiometry

Module 4: Neuro (17 decks)

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