Hearing Flashcards
(14 cards)
What is sound?
A travelling pressure wave.
What are the 2 variables in sound?
- Frequency (pitch)
- Amplitude (loudness)
What are the 2 wave properties?
condensation and rarefraction
What is an impedance transformer?
to amplify the sound
What is a sound transducer?
to convert the vibrations into electrical signals
How does the middle ear transmit vibrations?
- Malleus attached to tympanic membrane
- Vibration of membrane and so malleus
- Malleus attached to incus
- Incus attached to stapes
- Foot of stapes fits into the oval window
What are the middle ear parts?
- Malleus (hammer)
- Incus (anvil),
- Stapes (stirrup)
How is air pressure maintained in the middle ear?
Mastoid air cells
Eustachian tube
Unequal pressures can distort the eardrum
What is the Sound attenuation reflex, what does it respond to and what does it do to the eardrum?
Responds effectively to low frequency sounds
Will decrease up to 100 fold the energy that reached the eardrum.
It is a slow reflex
Useless against gun shot sounds (~140db)
Only lasts up to ~ 10 minutes
What is the function of the inner ear?
Hearing and balance
What does the boney labyrinth consist of?
Cochlea - hearing
Vestibule - balance
Semicircular canals - balance
What is the cochlea and where are they embedded?
Specialised sensory hair cells
No axons
Basilar regions covered with synaptic terminals of sensory neurons
Embedded in the tectoral membrane
What are the 2 tests for deafness?
Weber’s test
tuning fork middle of skull
inner ear damage - heard on healthy side
middle ear damage - heard on affected side
Rinne’s test
tuning fork on mastoid process, when no longer heard then use sound conduction
if hear it, Rinne +ve, then O.K.
if not, Rinne -ve, then conductive deafness
How is the cochlea organised?
tonotopically
