1b// The Auditory System

Question 1

What do vestibular and hearing organs do?

Answer 1

Vestibular organ: capture low frequency motion (movements)

Hearing organ: capture high frequency motion (sound)

Question 2

What cells do cochlea and canals come from?

Answer 2

stotocyst

Question 3

What is frequency/ pitch (Hz)?

Answer 3

cycle per second, perceived tone

Question 4

What is amplitude/ loudness (dB)?

Answer 4

Sound pressure, subjective attribute correlated with physical strength

Question 5

What is the humans range of hearing?

Answer 5

Frequency: 20–20,000Hz

Loudness: 0 dB to 120 dB sound pressure level (SPL)

Question 6

What are the outer ear functions?

Answer 6

To capture sound and to focus it to the tympanic membrane.

Modest amplification (10DB) of upper range of speech frequencies by resonance in the canal.

To protect the ear from external threats.

Question 7

What is the function of the middle ear?

Answer 7

The main function of the middle ear is mechanical amplification (can provide an additional 20-30dB)

Question 8

What is the hearing part of the inner ear?

Answer 8

cochlea

Question 9

What is the function of the cochlea/ inner ear?

Answer 9

Its function is to transduce vibration into nervous impulses

It does so in a way that captures the frequency (or pitch) and intensity (or loudness) of the sound

Question 10

How many compartments in the cochlea? And what are they?

Answer 10

3

scala vestibuli
scala tympani
scala media

Question 11

What are the scala vestibuli and scala tympani?

Answer 11

Bone structures, contain perilymph (high in sodium)

Question 12

What is the scala media?

Answer 12

Membranous structure, contains endolymph (high in potassium). Here is where the hearing organ or Organ of Corti is located.

*depending on frequency it will go through media at a certain point

Question 13

What lies in the basilar membrane?

Answer 13

the organ of Corti

Question 14

How is the basilar membrane arranged?

Answer 14

Basilar membrane is arranged tonotopically, using the same principle as a xylophone

Question 15

What is the hearing organ?

Answer 15

the organ of corti

Question 16

What does the organ of corti contain?

Answer 16

1) Inner hair cells (IHC) and
2) Outer hair cells (OHC)

Question 17

What is above the hair cells?

Answer 17

tectorial membraine

Question 18

What does the tectorial membrane do?

Answer 18

allows hair deflection, which in turn will depolarise the cell.

Question 19

What do inner hair cells do?

Answer 19

IHC carry 95% of the afferent information of the auditory nerve. Their function is the transduction of the sound into nerve impulses.

Question 20

What do outer hair cells do?

Answer 20

OHC carry 95% of efferents of the auditory nerve. Their function is modulation of the sensitivity of the response.

Question 21

What are the hairs of the hair cells called?

Answer 21

stereocilia

Question 22

What is the longest stereocilia called?

Answer 22

kinocilium

Question 23

How do stereocilia work and what do they do?

Answer 23

The deflection of the stereocilia towards the longest cilium (kinocilium) will open K+ channels (influx of K+)= depolarisation

This depolarises the cell releasing the neurotransmitter to the afferent nerve which then depolarises.

Higher amplitudes (louder) of sound will cause greater deflection of stereocilia and K+ channel opening

AKA TRANSDUCTION

*away from kinocilium= hyperpolarisation

Question 24

WHat causes depolarisation and hyper-polarisation in transduction? (ion wise)

Answer 24

depolarisation= open K+
hyper= closes k+

Question 25

Describe the differences between IHC and OHC. - arrangement - contact with tectorial membrane - carries what info - function

Answer 25

Question 26

Describe the auditory pathways.

Answer 26

Spiral ganglions via the vestibulo-cochlear nerve (CN8) travel to the ipsilateral cochlear nuclei (monoaural neurons) in the brainstem (pons) Auditory information crosses at the superior olive level After this point all connections are bilateral

Question 27

What are the types of hearing loss?

Answer 27

conductive hearing loss sensorineural hearing loss central hearing loss sudden or progressive hearing loss

Question 28

What is the difference between sudden and progressive hearing loss?

Answer 28

Sudden hearing loss minutes to days Progressive hearing loss months to years

Question 29

What is conductive hearing loss?

Answer 29

problem is located in outer or middle ear

Question 30

What is sensorineural hearing loss?

Answer 30

the sensory organ (cochlear) or the nerve (auditory nerve) 90% of all hearing is lost

Question 31

What are causes of conductive hearing loss?

Answer 31

outer ear= wax, foreign body middle ear= otitis, otosclerosis

Question 32

What is otitis?

Answer 32

Bubbles can be seen through the ear drum, suggesting there is liquid inside the middle ear. due to inflammation/ infection (bac or viral)

Question 33

What can you use to see inside the ear?

Answer 33

otoscope

Question 34

What is otosclerosis?

Answer 34

formation of new bone around the base of the stapes aka extra bone, it is progressive and common in young women

Question 35

What are causes of sensorineural hearing loss?

Answer 35

inner ear= noise, presbycusis, ototoxicity nerve= acoustic neuroma (vestibular schwannoma) (unilateral)- can press on CN8

Question 36

What are clinical bedside tests for hearing?

Answer 36

whisper in ipsilateral ear whilst rubbing fingers in contralateral ear tuning fork (weber and rinne test)= assesses the presence of gross hearing loss

Question 37

What is an audiogram? And what does hearing loss look like in one?

Answer 37

The audiogram is where the hearing thresholds are plotted to define if there is a hearing loss or not. A normal hearing threshold is located between 0 – 20dB *the decibels are going up to be heards headphones that make a clicking sound, can also put on mastoid*

Question 38

What do conductive and sensorineural hearing loss look like in audiometry?

Answer 38

*normal for conductive hearing loss when its bone conduction

Question 39

What type of sound does the normal cochlea produce?

Answer 39

The normal cochlea produces low-intensity sounds called Otoacoustic Emissions (OAEs)

Question 40

What specific cells produce Otoacoustic emissions (OAEs) and when?

Answer 40

These sounds are produced specifically by the outer hair cells as they expand and contract

Question 41

How can hearing loss be monitored on new borns?

Answer 41

otoacoustic emissions (OAEs) This test is often part of the newborn hearing screening and hearing loss monitoring.

Question 42

What is the treatment for hearing loss? (4)

Answer 42

underlying cause cochlear implants hearing aids brianstem implants