Piri Lecture 1 Flashcards
what are the steps of the auditory system
-sound waves transport energy which travels through the outer ear via the auditory canal and through the tympanic membrane (middle ear)
-they trigger hair cells on the cochlea’s organ of corti (inner ear) releasing neurotransmitters onto spiral ganglion cells
-spiral ganglion cells send information to the cochlear nuclei, superior olive, inferior colliculus, then to the thalamus, then finally the primary auditory complex
infrasound
less than 20Hz (frequency lower than what humans can perceive)
ultrasound
more than 20kHz (frequency higher than what humans can perceive)
auditory canal
-“closed tuber resonator” (enhances sounds bw 2kHz and 5kHz
–part of the outer ear
-outer window exerts 20x pressure onto the tympanic membrane causing the amplification of the sound waves
parts of the middle ear
-tympanic membrane
-ossicles (malleus, incus, stapes)
-eustachian tube
what does the eustachian tube do
attentuation reflex
contraction of muscles which are supposed to adjust fluid and amplify sound waves in the oval window/cochlea, protects against harmfully loud sounds
perilymph
fills scala vestibuli and scala typani
endolymph
fills scala media
endolymph is _________ positive than perilymph which is important for the creation of _____________
more, endocochlear potential
high concentration of sodium, low concentration of potassium
perilymph, scala vestibuli, scala tympani
high concentration of potassium, low concentration of sodium
endolymph, scala media, due to the stria vascularis potassium pump maintaining this concentration
if you unwind the cochlea, it is wider at the ______ and narrower at the _________
base, apex
helicotrema
hole in the apex of the cochlea which connects the scala vestibuli and scali tympani (perilymphs)
the basilar membrane is wider at the ________ and narrower at the __________
apex, base
t/f: the basilar membrane is most stiff at the base and least stiff at the apex
true
where do lower sound frequency waves travel to in the basilar membrane
the apex
where do higher sound frequency waves travel to in the basilar membrane
the base (not as far)
what is the organ of corti
the sensory area of the cochlea
what do inner hair cells primarily synapse with
sensory afferents
what do outer hair cells primarily synapse with
sensory efferents
how are hair cells depolarized
-when stereocillia lean towards the largest stereocillium, tip links joining each stereocillium potassium channels loosen and potassium mechanoreceptor ion channels open
-stereocillia are in the endolymph (scala media), so high external potassium causes an influx into hair cells (depolarization)
-depolarization then causes the opening of voltage gated calcium channels downstream resulting in NT release
which kind of hair cells detect most sound information
inner hair cells
phase locking
the regular/pattern following consistent firing of hair cells for a given sound frequency, lost at higher frequencies
lesion in the cochlear nucleus
ipsilateral loss of hearing
lesion in the superior olive
partial loss of hearing
lateral superior olive
encodes sound location through intensity differences,
-opposite side LSO is inhibited
conductive hearing loss
issue w conduction of hearing loss in the outer or middle ear,
sensorineural hearing loss
issue in cochlea/inner ear or pathway from cochlea to the brain
left belt hemisphere of cortex
plays important role in speech processing
right belt hemisphere of cortex
plays important role in tonal stimuli and music
intraural time difference
-mechanism used to understand the location of sounds with frequencies under 2kHz
-accomplished via MSO neuron which fires most strongly when there are coincident synapses from the left and right ear sound waves
-if the sound is closer to the left ear, coincidence will occur farther away from left than right (sound wave via left ear will have more time to travel to MSO)
