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Flashcards in Auditory pathway Deck (45):
1

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

1. cochlear
2. internal acoustic meatus

2

What type of energy does the external ear transmit?

sound waves

3

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

Sound waves to mechanical

4

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

mechanical to electrical

5

What cranial nerves run through the internal acoustic meatus?

vesitbulocochlear nerve (CN VIII)

facial nerve (CN VII)

6

What is the petrous part of the temporal bone like?

very hard

7

What is the ear drum known as?

tympanic membrane

8

What does the auditory tube do?

Connects to nasopharynx

enables air passage to maintain equilibrium of pressure

- goes wrong in planes

9

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

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

10

What also increases infection risk especially concerning nerves?

holes which nerves pass through

11

What is the inner ear?

series of fluid filled cavities

12

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?

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

perilymph

13

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

runs through the cochlea

contains endolymph

14

What is the cochlear duct?

a membranous sac (closed tube) contain endolymph

15

What is the ion conc like in endolymph?

low sodium

high potassium

16

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

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

17

What type of lymph does the cochlea contain?

perilymph

18

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

1. scala vestibuli
2. scala tympani

19

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

apex of cochlea - helicotrema

20

How is sound transmitted in the cochlea?

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

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

roof - vestibular membrane

floor - basement membrane

22

What is the auditory receptor?

The spiral organ (of Corti) on the basilar membrane

23

What does the spiral organ contain?

hair cells with the tips embedded into the tectorial membrane

24

What is the spiral organ stimulated by?

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

25

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

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

What are primary auditory fibres?

axons of bipolar neurone in spiral ganglion

27

What do the primary auditory fibres form?

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

28

Where does the primary auditory fibres enter?

brainstem at cerebellopontine angle

29

Where does the primary auditory fibres synapse with secondary neurons?

in ventral and dorsal cochlear nuclei

30

What are the auditory centres in the brain stem?

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

31

Is the auditory pathway polysynaptic?

yes

32

Why is the auditory pathway bilateral?

so sound can be localised as it compares 2 inputs

33

What 2 inputs does the bilateral auditory pathway compare?

1. timing
2. loudness

34

How does the basillar membrane respond to sound?

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

35

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

low pitch

36

Where does sound information of low pitch project to?

anterolateral part of Heschl's gyrus

37

What hemisphere houses the 2ndary auditory area?

left

38

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

1. Brocas - anterior and motor production of words

2. wernickes - posterior and sensory and understanding

39

What is aphasia a result of?

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

40

What supplies wernicke's and broca's?

middle cerebral artery

41

Would a unilateral lesion have any effect on hearing?

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

42

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

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

43

What is conductive deafness?

defect of sound transmission up to spiral ganglion

44

What is sensorineural deafness?

defect in function of spiral ganglion or cochlear nerve

45

What combination of deafness could you get?

conductive and sensorineural