Hearing Flashcards
What is sound?
Longitudinal waves- rapid variation of air pressure
What is wavelength and frequency?
Wavelength- diff between two peaks
Frequency- rate the pressure cycles compression > rarefaction
F and W are inversely related
What is normal air pressure?
100KPa
What is the function of the pinna?
Gathers air from around and funnels into the eardrum
Made of cartilage and covered with skin
What is the cochlea?
Fluid filled spiral canal separated by a flexible membrane
Difference between two sides of cochlea
Start narrow and stiff, end wide and compliant
What are the functions of the ossicles
Connect tympanic membrane to cochlea
What filters sound according to frequency?
basilar membrane
where is the organ of corti
On top of basilar membrane within the scalia media
shapes of stereocillia
inner hair cells and outer hair cells
inner hair cells - in a line
outer - rows of 3 in dome shames
How do hair cells work
the hair cells bend one way causing depolarisation and bend another way causing repolarisation. the hair cells are attached to afferent neurones so APs are generated during depolarisation (right excitation left inhibition)
what are transduction links
in hair cells join the cillia together causing increased ion entry making the depol / hyperpol bigger
What is the cochlear amplifier
theyre motile therefor increased vibrations in the basilar membrane - amplifies quiet sound not loud
describe the two types of hearing loss
conductive - abnormality before cochlea
Sensorineural- in cochlear or auditory nerve (loss of hair cells or hair cell function)
what is Deafferentation and when does it occur
• Detachment of nerve fibres from inner hair cells.
Occurs with mild noise exposure, and possibly linearly with age
through very normal levels of environmental exposure to sound.
