34: How We Hear Flashcards
Amplitude of sound
Sound intensity measured in decibels
Sound frequency
Number of oscillations of air pressure per second (Hz)
Basilar membrane near oval window vs near helicotrema
Near oval window: narrow and stiff: max motion for high frequency
Near helicotrema: wider and flexible: max motion for low frequency
Where is the stria vascularis and what does it do?
In scala media, produces endolymph
Function of the high endocochlear potential in the scala media
Drives positively charged ions into hair cell
What forms the blood-labyrinth-barrier (BLB)?
Stria vascularis
Function of the BLB
Main site of drug entry to inner hair cells, sometimes to its detriment (ototoxic drugs)
Hair cell cell type - explain
Mechanoreceptors - receive afferent and efferent input, but are not neural - they convert mechanical signals into electrical
Hair cell histo
Epithelia
What is on the apical and basal side of a hair cell?
Apical: stereocilia
Basal: neural synapse
What happens if hair cell stereocilia deflect in the opposite direction?
Hyperpolarization
Why are outer hair cells contractile?
Boosts the mechanical vibrations of the basilar membrane -> amplification
What causes otoacoustic emissions?
Retrograde movement from contractile outer hair cells -> towards oval window and through ear ossicles, making a sound on the TM
Where do olivocochlear efferents originate from?
Superior olivary complex
Otoacoustic emissions: when are they measured?
In infants to assess ear function, testing for tinnitus, hearing loss, or ototoxicity
