How we hear

Question 1

outer/middle ear defect

Answer 1

conductive hearing loss

outer/middle ear amplify sound

Question 2

inner ear defect

Answer 2

sensorineural hearing loss

Question 3

drugs causing ototoxicity*

Answer 3

aminoglycosides
quinine (treat malaria)
loop diuretics
chemotherapeutic drugs
local antiseptics

Question 4

air conduction louder than bone conduction

Answer 4

normal - bone conduction bypass amplification of the mid/outer ear
inner ear (sensorineural hearing loss) - air conduction still benefits from the amplification compared to bone (bypasses amplification from the outer and middle ear), even though both will be softer

Question 5

bone conduction louder than air conduction

Answer 5

middle/outer ear (conductive hearing loss)

conductive deafness - sounds die out -> air conduction will be poor, bone better

Question 6

sensorineural hearing loss weber test

Answer 6

side with the problem (abnormal) will hear it softer

signal received in inner ear is less -> softer

Question 7

conductive hearing loss weber test

Answer 7

side with the problem (abnormal) will hear it louder
both inner ears receive same signal
but cause there is obstruction in outer/middle ear -> less background noise from that problem side -> hear the signal on forehead better

Question 8

cause external ear obstruction

Answer 8

ear wax (cerumen)
otitis externa
perforated ear drum

Question 9

middle ear problems

Answer 9

suppurative otitis media
- likely to happen in young children: horizontal eustachian tube -> easier spread of infection caused by nasal congestion to ear

developmental: 2nd branchial arch malformation

Question 10

causes of sensorineural hearing loss

Answer 10

noise induced hearing loss
age related: presbycusis
ototoxic medications

intracranial tumour
auditory neuropathy

Question 11

how do we hear

Answer 11

5Cs

• collection
• conduction of acoustic energy
• conversion
• conduction of electrical energy
• comprehension

Question 12

middle ear structures + related structures

Answer 12

malleus
incus

nearby: chorda tympani - taste for ant 2/3 tongue

Question 13

middle ear fn

Answer 13

reduce reflection of sound caused by impedance mismatch by:

• TM (tympanic membrane) to oval window ratio
• ossicular coupling
• ear drum buckling action -> increase pressure

Question 14

inner ear structures

Answer 14

organ of corti - contains hair cells (3 rows of outer, 1 row inner)

• outer: amplification of sound, signal modulation
• inner: signal transducer

apex for lower freq
base for higher freq

Question 15

assessing hearing fn

Answer 15

audiometry

Question 16

treatment for hearing loss

Answer 16

hearing aids: amplify sound frequency

cochlear implantation: stimulate spiral ganglion cells of auditory nerve