Topic 6: Auditory System Flashcards
What cranial nerve carries both auditory & vestibular information?
CN VIII
How are sound characterized?
by frequency (pitch/Hertz)
amplitude (loudness/ decibel)
What are the three bones of middle ear? What do they do?
malleus, incus and stapes
transfer sound waves into inner ear & amplify it
tympanic membrane
seperate external ear from middle ear
What is frequency of sound characterized with?
the number of sound waves/ second
How are the anatomy of hearing & balance similar?
the cochlea & vestibular apparatus are closely connected
sensory receptors in both are hair cells
what is the amplitude of sound characterized with?
height of waves
What does eustachian tube do?
connects the middle ear and pharynx
help maintain equal pressure on both sides of eardrum by allowing outside air to enter the middle ear
What is the funciton of external ear?
directing the soundwaves to middle & inner ear
amplify sound waves at the frequencies of human speech
perilymph
How is the perilymph different from the inside of cell? (amount of K+, Na+)
space btw bony & membranous labyrinth
low K+, high Na+
what part of inner ear is responsible for sound processing?
cochlea
where does the stapes of middle ear push in when sound pressure is high?
oval window
What part of inner ear are associated with vestibular system?
semicircular canals, saccule, & utricle
what happen when stapes push in the oval window?
the pressure fluid (endolymph) increases & the round window bulge outward
how are the receptors in semicircular canal, ultricle & saccule activated?
by head movements
endolymph
How does endolymph similar to the inside of cell?
the fluid inside the membranous labyrinth
high in potassium & low sodium
Structure of inner ear?
bony and membraneous labyrinth
Where are the sounds receptors activated?
cochlea
vestibule
connect cochlea & semicircular canals
What does cochlea transduces? What does cochlea consists of?
sound waves into neural impulses
3 parallel canals: scala vestibuli, scala media & scala tympani
scala tympani
What window (oval or round) does scala tympani meet with?
what does it contain with?
one of the canal of cochlea
round window
perilymph
where does the bony labyrinth locate? membranous labyrinth?
within the temporal bone
suspended within the bony labyrinth
what receptors does the inner ear have?
auditory & vestibular receptors
Where does the organ of Corti locate?
What does it have?
on top of basilar membrane
auditory receptors- hair cells
stereocilia
kinocilium
group of hair cells
single hair cell
Reissner’s membrane
seperate scala vestibuli & scala media
At the apex of cochlea, what happen?
the scala media closed off
scala vestibuli & scala tympani connect via helicotrema
What does scala media contain?
endolymph
Where do hair cells actually locate?
When there is a sound wave, what happen to hair cells?
btw basilar memmbrane and tectorial membrane
they bend and become depolarization or hyperpolarization
where does tectorial membrane locate?
hang over the Organ of Corti
scala vestibuli
what window (oval or round) does it meet with?
what does it contain?
one of the canal of cochlea
oval window
perilymph
Basilar membrane
How does it help auditory system generate action potentials?
seperate scala media & scala tympani
when there is sound wave, basilar membrane moves, causing hair cells move to generate action potentials
How does the basilar membrane structure change from apex to base?
How does this structure affect to its ability to analyze the frequency?
It is wider & flexible at apex -> low frequency
It is stiffer & smaller at base -> high frequency
how does tonotopic map in auditory system different from in cortex?
in cortex, low frequency is analyzed in rostral side
high frequency is analyzed in caudal side
In auditory system, low frequency is at apex (caudal side)
high frequency is at base (rostral side)
helicotrema
Why is this structure important?
the perilymph flow (connection) btw scala vestibuli & scala tympani
the pathway of pressure waves move from oval window -> round window
What are two ways that loudness is encoded in?
Explain each
firing rate - more intense stimulus -> more vibration on basilar membrane -> polarizing hair cells more
number of active neurons - more intense stimuli -> larger response of the basilar membrane -> activating more hair cells
Where is the base of cochlea?
Where is the apex of cochlea?
at the oval window
at the top of cochlea where scala media closes off
What is the fluid that inside of membranous labyrinth?
endolymph
What are the auditory informations that being sent to auditory cortex?
timing of sounds
directionality of sound
frequency contents of sound
where is the 1st order neurons of auditory pathway?
2nd order neurons ?
spiral ganglion
dorsal & ventral cochlear nucleus in rostral medulla
In where of the auditory pathway producing topography map of auditory space?
inferior colliculus
Where is the 1st place that the auditory information start to project bilaterally to the cortex?
superior olive
Where is the 1st stage of selectivity for combination of frequencies?
medial geniculate nucleus
what do we have when auditory information reach auditory cortex?
conscious sound perception
in where of the auditory pathway, directionality of sound is determined?
superior olive
How is the directionality of sound determined?
by difference in time & amplitude to each ear
Where is the convergence of all binaural inputs?
inferior colliculus
What is the space that btw membranous & bony labyrinth?
perilymph
If we have a lesion on the left side of dorsal cochlear nucleus, what will hapen?
you can’t determine the frequency contents of sound on left ear
If you have a lesion on one side of superior olive, will you still hear normally?
yes, you still hear normally
because the auditory information bilateral projects at superior olive to auditory cortex
Damage to what can result in the deafness?
middle ear
cochlea
CN VIII
what does circuitry in localization of low frequency (<3kHz) sound depend on?
depend on time difference reaching btw each ear
What side of superior olive (medial/ lateral) is in synaptic connects with ventral cochlear nucleus for localization of low frequency (<3kHz) sounds?
medial superior olive
Why is medial superior olive significant in localization of low frequency sounds?
MSO acts as coincidence detector that will fire action potentials only when sound information in both ears reach MSO
what does circuitry in localization of high frequency (>3kHz) sound depend on?
difference in loudness of the sound in each ear
How does circuitry in localization of low frequency (<3kHz) sound pathway work?
What is the result of this pathway?
ventral cochlear nucleus excites lateral superior olive (LSO) -> activate medial nucleus of trapezoid body (MNTB) -> inhibit LSO in other side of different ear
strong stimulus to the ipsilateral ear
What part of the ear amplify the soundwaves at frequencies of human speech?
external ear
binaural inputs
the fusion of all auditory informations ( timing of sound, directionality & frequency contents of signal)
