Lecture 15: Auditory/Vestibular Systems Flashcards
Describe the sound transduction pathway
Sound enters at pinna, vibrates the tympanic membrane. This vibrates the ossicles (malleus, incus, stapes) which vibrates the oval window. This causes fluid (perilymph) to vibrate in the scala vestibuli which causes the basilar membrane to shift. this will cause the tiplinks in the hair cells to stretch towards the tallest stereocilium, opens up K+ channels, and cause depolarization. Signals will transfer from the vestibulocochlear nerve (nerve 8) to the cochlear nuclei in the brainstem. It then goes from the dorsal/ventral cochlear nuclei to the inferior colliculus and then to the medial geniculate nucleus of the thalamus. From there it synapses with the auditory cortex in the temporal lobe
Describe the vestibular transduction pathway (both rotational and linear acceleration)
Semicircular canals sense rotary acceleration. Has extension called ampulla, within is cupula that occludes lumen. When endolymph fluid shifts, causes hair cells to stretch and if towards kinocilium, will depolarize. head rotating in one direction causes fluid to move in the other direction.
Otolith organs sense linear acceleration. Has otoliths (calcium carbonate crystals) in the gelatinous cap, high specific gravity. When it shifts, it will cause hair cells to depolarize.
Goes to the vestibular nuclei in the brain stem via nerve 8, then to various connections (cerebellum, oculomotor nuclei, vestibulospinal tract)
Discuss the anatomy of the cochlea
perilymph in the scala vestibuli and scala tympani, endolymph in the scala media
round window is where it exits
helicotrema is the apex of the basilar membrane, it’s wide and floppy at the apex
tectorial membrane touches tip-links
Discuss the tonotopic organization of the cochlea
depends on where the basilar membrane is vibrated, requires different frequencies to vibrate and activate the hair cells. Wide and floppy (low frequency) at tip, stiff and narrow (high frequency) at base
