Flashcards in Sensory Transduction: Auditory and Vestibular System Deck (25):
what ion causes depolarisation to occur in the hair cells of the ear?
K+ influx from endolymph
explain how the hair cells cause sensory afferent signals to be produced?
cilia move towards kinocilum
K+ channels open due to tip link
hair cell depolarises
Ca2+ channels open
vesicles of glutamate released to synapse with sensory afferent neurone
more APs are generated when cilia move towards kinocilum - true or false?
what are the ganglia of scarpa and where are they located?
located in vestibular nerve just after CNVIII splits
contain cell bodies of sensory neurones
explain how sound is produced and how we hear it?
object (eg vocal cord) vibrate
air pressure changes
air vibrates in 3 dimensions towards ear
causes eardrum, incus, malleus and stapes to vibrate
stapes footplate vibration causes fluid in cochlea to move over hair cells (transduction)
what properties of the middle ear make it useful at amplifying sound?
area ratio of tympanic membrane to stapes footplate is 20:1 (decreasing area over which the noise is exerted increases the pressure of noise)
lever action of the ossicles (malleus higher than incus) - increases pressure of noise
buckling of ear drum - middle is attached to malleus therefore moves less and preserves force
what membrane separated the scala vestibuli and media?
what membrane separated scala media and tympani?
which of the scala vestibuli, media and tympani regress at the apex of the cochlea?
media no longer exists - fluid in scala vestibuli and tympani mix
what is meant by the tonotopy of the basilar membrane?
particular spatial arrangement of frequencies detected
the basilar membrane vibrates within the fluid of the cochlea - true or false?
true - it is flexile and therefore can move with fluid
it is the widest and floppiest at the apex
do we have more inner or outer hair cells?
outer (15000-20000 compared to 3500 inner)
what is the role of the tectorial membrane?
vibrates and brushes against hair cells, making them move and release neurotransmitter
what ganglion is located near the organ of corti, containing sensory neuron cells?
why must potassium be redistributed into the endolymph?
causes problems such as deafness otherwise
mutations in any genes coding for K channels or transporters have the potential to cause deafness
how do the outer hair cells amplify found?
have motor proteins on their sides which get compressed and change the length of overall hair cell
this moves the basilar membrane more, and the inner cell moves with this membrane
inner hair cell then fires more sensory afferent transduction signals
describe the pathway from the cochlea to the primary auditory cortex?
cochlea -> cochlear nuclei -> superior olivary nuclei -> nucleus of lateral leminiscus -> inferior colliculus -> medial geniculate nucleus -> primary auditory cortex
which nuclei in the brainstem is important for the localisation of sound in space and how does it do this?
superior olivary nucleus - senses time at which sound reaches ear (intra-aural time difference)
what is the calyx of held?
large nerve terminal ending with lots of vesicle active zones ready to discharge upon signal
they usually react to high frequency sounds
what 2 questions does the vestibular system function to answer?
where am i going?
which way is up?
what do the semicircular canals sense?
head angular acceleration (rotation)
what do the utricle and saccule detect?
head linear acceleration
saccule = vertical movement
utricle = horizontal movement
which of the semicircular canals share a plane?
left anterior and right posterior (and vice versa)
both horizontal are also in same plane
what is the otocania?
CaCO3 bio-crystals which help mechanical forces to reach the sensory hair cells in the utricle and saccule