Auditory pathway

Question 1

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

Answer 1

1. cochlear

2. internal acoustic meatus

Question 2

What type of energy does the external ear transmit?

Answer 2

sound waves

Question 3

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

Answer 3

Sound waves to mechanical

Question 4

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

Answer 4

mechanical to electrical

Question 5

What cranial nerves run through the internal acoustic meatus?

Answer 5

vesitbulocochlear nerve (CN VIII)

facial nerve (CN VII)

Question 6

What is the petrous part of the temporal bone like?

Answer 6

very hard

Question 7

What is the ear drum known as?

Answer 7

tympanic membrane

Question 8

What does the auditory tube do?

Answer 8

Connects to nasopharynx

enables air passage to maintain equilibrium of pressure

• goes wrong in planes

Question 9

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

Answer 9

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

Question 10

What also increases infection risk especially concerning nerves?

Answer 10

holes which nerves pass through

Question 11

What is the inner ear?

Answer 11

series of fluid filled cavities

Question 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?

Answer 12

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

perilymph

Question 13

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

Answer 13

runs through the cochlea

contains endolymph

Question 14

What is the cochlear duct?

Answer 14

a membranous sac (closed tube) contain endolymph

Question 15

What is the ion conc like in endolymph?

Answer 15

low sodium

high potassium

Question 16

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

Answer 16

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

Question 17

What type of lymph does the cochlea contain?

Answer 17

perilymph

Question 18

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

Answer 18

1. scala vestibuli

2. scala tympani

Question 19

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

Answer 19

apex of cochlea - helicotrema

Question 20

How is sound transmitted in the cochlea?

Answer 20

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

Question 21

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

Answer 21

roof - vestibular membrane

floor - basement membrane

Question 22

What is the auditory receptor?

Answer 22

The spiral organ (of Corti) on the basilar membrane

Question 23

What does the spiral organ contain?

Answer 23

hair cells with the tips embedded into the tectorial membrane

Question 24

What is the spiral organ stimulated by?

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What are primary auditory fibres?

Answer 26

axons of bipolar neurone in spiral ganglion

Question 27

What do the primary auditory fibres form?

Answer 27

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

Question 28

Where does the primary auditory fibres enter?

Answer 28

brainstem at cerebellopontine angle

Question 29

Where does the primary auditory fibres synapse with secondary neurons?

Answer 29

in ventral and dorsal cochlear nuclei

Question 30

What are the auditory centres in the brain stem?

Answer 30

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

Question 31

Is the auditory pathway polysynaptic?

Answer 31

yes

Question 32

Why is the auditory pathway bilateral?

Answer 32

so sound can be localised as it compares 2 inputs

Question 33

What 2 inputs does the bilateral auditory pathway compare?

Answer 33

1. timing | 2. loudness

Question 34

How does the basillar membrane respond to sound?

Answer 34

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

Question 35

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

Answer 35

low pitch

Question 36

Where does sound information of low pitch project to?

Answer 36

anterolateral part of Heschl's gyrus

Question 37

What hemisphere houses the 2ndary auditory area?

Answer 37

left

Question 38

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

Answer 38

1. Brocas - anterior and motor production of words | 2. wernickes - posterior and sensory and understanding

Question 39

What is aphasia a result of?

Answer 39

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

Question 40

What supplies wernicke's and broca's?

Answer 40

middle cerebral artery

Question 41

Would a unilateral lesion have any effect on hearing?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

What is conductive deafness?

Answer 43

defect of sound transmission up to spiral ganglion

Question 44

What is sensorineural deafness?

Answer 44

defect in function of spiral ganglion or cochlear nerve

Question 45

What combination of deafness could you get?

Answer 45

conductive and sensorineural