PHYS phys of the auditory and vestibular systems Flashcards
Endolymph is similar to
bathes what end of the hair cell
ICF
bathes apical end
Perilymph is similar to
bathes what end of the hair cell
ECF
bathes basal end
where is maximal motion for high frequencies located in the cochlea
at base
where is maximal motion for low frequencies located in the cochlea
more apically
what type of receptors are hair cells
mechanoreceptors
electrochemical driving results from what two factors
large endolymphatic potential (high [K] in endolymph)
large electrical gradient (scala media has high + charge ~+80mV)
deflection of stereocilia toward kinocilium
depolarization of hair cells
deflection of stereocilia away from kinocilium
hyperpolarization of hair cells
what opens the channels on hair cells
stereocilia are linked by “chains”
depending on direction of deflection, Ca/K channels can be opened
K open –> depol. –> Ca channels open
what are the ion channels on the stereocilia
what ion do they transport
what is their purpose
TRPA1
K
allow K influx to depol cell when stereocilia deflect toward kinocilium
what do hair cells release in response to influx of Ca
Glutamate
what maintains the electrochemical properties of the endolymph
stria vascularis
how many inner hair cells and how many outer hair cells are there on the basilar membrane
one row of inner hair cells
three rows of outer hair cells
f(x) of inner hair cells
primary source of auditory information
what makes the outer hair cells contractile
prestin
f(x) of outer hair cells
acts as an amplifier
what type of afferent neuron takes information from the inner hair cell to the spiral ganglion
type 1 neuron (95%)
what type of afferent neuron takes information fom the outer hair cell to the spiral ganglion
type 2 neuron
where do hair cells receive efferent innervation from
superior olivary complex
what is the primary nuclei of the superior olivary complex
medial superior olivary nucleus (MSO)
lateral superior olivary nucleus (LSO)
what is the first site in the brainstem where information from both ears converge
superior olivary complex
essential to accurately localize sound
f(x) of MSO
generate a map of interaural time differences
helps the localization of sound
under what conditions does the MSO respond the strongest
when 2 inputs arrive simultaneously
f(x) of LSO
generate a map of interaural intensity differences
helps localize source of sound
site of sound localization excites ipsilat. side LSO and receives inhib. from contralat. side, but excite>inhib.
f(x) of primary auditory cortex (A1)
essential in conscious perception of sound
beginning to interpret of sound
in the primary auditory cortex, which end (rostral/caudal) corresponds with high frequencies/low frequencies
more rostral end corresponds to apex of cochlea (low
frequency)
more caudal end corresponds to base of cochlea
(higher frequency)
secondary auditory complex f(x)
thought to respond to more complex sounds (music), identifying (naming) a sound, and speech
VCN f(x) (pierce)
nature of sound (high, low)
DCN f(x) (pierce)
location of sound
Inferior colliculus (IC) f(x)
suppresses information related to echoes
creates spatial map of sound
efferent input to the auditory system (3)
olivocochlear efferents (OC) middle ear muscle motorneurons autonomic innervation of the inner ear
OC efferents
origination
what do they innervate
originate from superior olivary complex
medial OC innervate outer hair cells
lateral OC innervate inner hair cells
OC efferents f(x)
shifts responses to higher sound levels?
decrease adaptation
reduce response to noise
may protect hair cells from damage to intense sounds
middle ear efferents
f(x)
tensor tympani to malleus (CN V)
stapedius to the stapes (CN VII)
bilat. response to high sound levels
contractions decrease transmission of sound
prevent damage
may preven low frequency masking ( improve speecch
discrimination)
two types of otoacoustic emissions
spontaneous - pure tones; probably generated from
movement of outer hair cells
evoked - used for testing hearing loss (n/a if damage
present)
Sensorineural hearing loss is caused by
damage to hair cells, nerve fibers or both
base is more susceptible to damage than apical end
effects of injury to outer hair cells
decrease in sensitivity (higher threshold) and broader tuning
effects of injury to inner hair cells
cuts off auditory input to CNS
what detects rotational acceleration
semicircular canals
anterior - falling forwards
posterior - falling backwards
horizontal - horizontal rotations (spin?)
what detects forward and backward linear acceleration
utricle
what detects up and down linear acceleration
saccule
vestibulo-optic reflexes
horizontal rotation
falling forward
falling backward
which m. involved in each
horizontal - medial rectus on same side of rotation
activated, lateral rectus inhibited (opposite for
contralat. eye)
falling forward - superior rectus activated, inferior
rectus inhibited
falling backward - superior oblique activated, inferior
oblique inhibited
