Auditory pathway Flashcards

1
Q

What is found in the petrous part of the temporal bone? (2)

A
  1. cochlear

2. internal acoustic meatus

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2
Q

What type of energy does the external ear transmit?

A

sound waves

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3
Q

What type of energy change occurs in the middle ear? (2)

A

Sound waves to mechanical

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4
Q

What type of energy change occurs in the inner ear? (2)

A

mechanical to electrical

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5
Q

What cranial nerves run through the internal acoustic meatus?

A

vesitbulocochlear nerve (CN VIII)

facial nerve (CN VII)

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6
Q

What is the petrous part of the temporal bone like?

A

very hard

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7
Q

What is the ear drum known as?

A

tympanic membrane

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8
Q

What does the auditory tube do?

A

Connects to nasopharynx

enables air passage to maintain equilibrium of pressure

  • goes wrong in planes
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9
Q

Why is the middle ear a high risk space? (5)

A
  1. connected to nasopharynx - prone to infection
  2. connected to mastoid air cells - infection may spread to middle cranial fossa
  3. internal jugular vein lies inferior - thrombosis risk
  4. internal carotid artery lies anterior - link to pulsatile tinnitus
  5. traversed by chord tympani and facial canal - infection risk
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10
Q

What also increases infection risk especially concerning nerves?

A

holes which nerves pass through

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11
Q

What is the inner ear?

A

series of fluid filled cavities

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12
Q

In the inner ear, what are the names of the series of cavities the petrous part of the temporal bone have and what do they contain?

A
  1. vestibule
  2. SSC - superior semicircular canal
  3. cochlea

perilymph

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13
Q

Where does the cochlear duct run through and what type of lymph does it contain?

A

runs through the cochlea

contains endolymph

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14
Q

What is the cochlear duct?

A

a membranous sac (closed tube) contain endolymph

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15
Q

What is the ion conc like in endolymph?

A

low sodium

high potassium

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16
Q

Things you need to know in inner ear? (5)

A
  1. posterior semicircular canal and duct
  2. vestibule
  3. lateral semi-circular canal and duct
  4. anterior semicircular canal and duct
  5. cochlea
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17
Q

What type of lymph does the cochlea contain?

A

perilymph

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18
Q

What two chambers does the cochlear duct separate the cochlea into?

A
  1. scala vestibuli

2. scala tympani

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19
Q

What are the two chambers scala vestibuli and tympani continuous of?

A

apex of cochlea - helicotrema

20
Q

How is sound transmitted in the cochlea?

A
  1. hydraulic pressure is created in the perilymph
  2. this pressure is created by vibrations of Stapes and pass to apex via the Scala vestibuli
  3. the vibrations pass through the helicotrema and descends via the Scala tympani to the round window
  4. as fluid moves around the cochlea it deforms the fluid, endolymph in the cochlear duct
21
Q

What makes up the roof and floor of the cochlear duct?

A

roof - vestibular membrane

floor - basement membrane

22
Q

What is the auditory receptor?

A

The spiral organ (of Corti) on the basilar membrane

23
Q

What does the spiral organ contain?

A

hair cells with the tips embedded into the tectorial membrane

24
Q

What is the spiral organ stimulated by?

A

the deformation of the cochlear duct by perilymph in the surrounding Scala vestibuli and scala tympani

25
Q

What components do you need to know of the cochlear duct and the things that surround the cochlear duct?

A
  1. vestibular emmbrane
  2. tectorial membrane
  3. cochlear nerve
  4. spiral ganglion
  5. scala tympani
  6. basilar membrane
  7. spiral organ
  8. cochlear duct
  9. scala vestibuli
26
Q

What are primary auditory fibres?

A

axons of bipolar neurone in spiral ganglion

27
Q

What do the primary auditory fibres form?

A

the cochlear nerve which becomes part of the vestibulocochlear nerve - CNVIII

28
Q

Where does the primary auditory fibres enter?

A

brainstem at cerebellopontine angle

29
Q

Where does the primary auditory fibres synapse with secondary neurons?

A

in ventral and dorsal cochlear nuclei

30
Q

What are the auditory centres in the brain stem?

A
  1. medial geniculate nucleus of the thalamus
  2. inferior collicus
  3. superior olivary nucleus
  4. cochlear nuceli
31
Q

Is the auditory pathway polysynaptic?

A

yes

32
Q

Why is the auditory pathway bilateral?

A

so sound can be localised as it compares 2 inputs

33
Q

What 2 inputs does the bilateral auditory pathway compare?

A
  1. timing

2. loudness

34
Q

How does the basillar membrane respond to sound?

A

different regions of the basillar membrane respond maximally to sounds of a different pitch

35
Q

What frequency of sound does the apex of the basilar membrane respond to?

A

low pitch

36
Q

Where does sound information of low pitch project to?

A

anterolateral part of Heschl’s gyrus

37
Q

What hemisphere houses the 2ndary auditory area?

A

left

38
Q

What does the 2ndary auditory area entail? (which areas)

A
  1. Brocas - anterior and motor production of words

2. wernickes - posterior and sensory and understanding

39
Q

What is aphasia a result of?

A

results of f=damage to speech areas - broca’s (non-fluent) or Wernickes (fluent)

40
Q

What supplies wernicke’s and broca’s?

A

middle cerebral artery

41
Q

Would a unilateral lesion have any effect on hearing?

A

no as the auditory pathway is bilateral however ability to localise sound may be impaired

42
Q

What must be affected in a person who is deaf (usually in both ears)?

A

the peripheral part of the auditory (up to the brain stem) must be affected

43
Q

What is conductive deafness?

A

defect of sound transmission up to spiral ganglion

44
Q

What is sensorineural deafness?

A

defect in function of spiral ganglion or cochlear nerve

45
Q

What combination of deafness could you get?

A

conductive and sensorineural