Special Senses: The Ear Flashcards
What are the two properties of sound waves? What is the unit of measurement and the normal range of each
- Frequency = distance in hertz, normal range 20-20,000 Hz
- Volume = pressure in decibels dB
Conversations are ~60 dB
At which dB does hearing become painful?
Sound becomes loud to the point of painful at 120 dB
How common is tinnitus in the UK? How many children are born with severe or profound hearing impairment?
Tinnitus: 1/10
Children born with severe or profound hearing impairment: 1/100
What does hearing loss predominantly increase with?
Age
What is Auditory transduction and where in the ear is it performed? Where does the ‘sound’ then travel?
Auditory transduction is the conversion of a sensory stimuli from one form to another by the organ of corti in the cochlear of the inner ear
Sound is then projected by the auditory pathway (Cn VIII) to the temporal lobe of the cortex
Describe how the structure of the basilar membrane (where the spiral organ of corti is) allows for auditory transduction?
There are 4 rows of hair cells
- 1 inner which provides most of the signal to CN VII
- 3 outer which modulates the response of the inner hair cells
What are the two auditory pathways? Briefly describe each and identify which is more commo
- Primary (lemniscal) pathway: the main pathway which auditory info reaches the primary auditory cortex
- Non-lemniscal pathway: mediates unconscious perception (i.e attention, emotional response and auditory reflexes)
* insert photo in pro
Why does a supranuclear lesion (above ocularmotor nuclei) not lead to hearing loss?
Because some fibres from each auditory pathway (lemniscal and non-lemniscal) cross over, so info from both ears travels bilaterally
Which preparations should you perform when about to do an otoscopy in adults vs in children <2?
In adults: pull the helix up and back to straighten the ear canal
In children <2: pull earlobe down
Describe how you would perform Rinne’s test, what is the normal finding?
Place fork at the external meatus and then the mastoid process and ask which is louder
*normal: should be louder at the external meatus as air conduction>bone conduction
Describe how you would perform Weber’s test, what is the normal finding?
Place tuning fork on the forehead in the midline and ask which ear has the loudest sound or if its heard loudest ‘centrally’ (i.e no difference)
*normal: loudest centrally
What is pure tone audiometry and what does it test?
It’s a quantitative hearing assessment that graphically shows the volume (dB)/y axis and particular frequency (Hz)/x axis of a noise that must be played to be heard - therefore it shows the nature and degree of hearing loss
Which type of hearing loss is the most rare?
Central: lesion in the auditory pathway in the brain
List the volume ranges for the following
a) normal hearing
b) mild hearing loss
c) moderate hearing loss
d) severe hearing loss
e) profound hearing loss
a) 0-25 dB
b) 26-40 dB
c) 41-55 dB
d) 71-90 dB
e) >90 dB
What is the difference between a hearing aid and a cochlear implant?
While a hearing aid can amplify sound, a cochlear implant transforms sound into electrical energy which can stimulate the auditory nerves in the inner ear