Sievert-Ear and Audition Flashcards
What makes up the external ear?
auricle and external auditory meatus
What does the external ear do?
Captures and funnels sound
What is the middle ear?
air-filled cavity behind the ear drum.
What is found in the middle ear and what do they do?
3 ossicles (malleus,incus and stapes), transfer ear drum vibration to oval window and fluid behind oval window
What is the inner ear?
fluid filed cochlea and vestibular apparatus
What is the function of the inner ear?
holds sensory hair cells for hearing and balance
Where do you find the semicircular canal?
inner ear
What many ducts make up the cochlea?
3 different ducts
Lots of functions of the inner ear also carry over to the (blank) system
vestibular
Where does the external auditory meatus come from?
the 1st brachial cleft
Where does the middle ear, auditory tube come from?
the 1st branchial pouch
Where does the malleus and incus come from?
the cartilage from the first branchial arch
Wher does the stapes come from?
the cartilage from the second branchial arch
What CN is associated with the malleus and incus? why?
CN 5
because Arch 1 is innervated by CN 5 and that is where the malleus and incus come from
What CN is associated with the stapes (means stirrup in latin colt in case you were wondering) and why?
CN 7 because arch 2 is innervated by CN 7 and this is where the stapes originates from
The bones of the ear develop via what process?
endochondrial ossification (cartilagenous model)
So the middle ear has the three ossicles which are the malleus, incus and stapes. What do these small bones do?
They transmit sounds from the air to the fluid filled labyrinth (cochlea)
What 2 small skeletal muscles alter movements of the ossicles?
tensor tympani and stapedius
How is the membranous labyrinth, hair cells and ganglion cells made and what are all of these a part of?
These are all part of the inner ear.
Made by the otic placode which will invaginate to form the otic pit/vesicle and statoacoustic ganglion
How do we get the surface ectoderm of the otic placode to make the inner ear?
it gets induced by neuroectoderm
How does the external ear keep bugs and bacteria out?
contain ceruminous glands that produce wax which is antibacterial
What are the lateral walls of the external ear made out of?
cartilagineous
What are the medial walls of the external ear made out of?
bone
Which part of the auditory canal is longer, the inferior or superior portion?
the inferior canal
Why is the external ear awesome at collecting sound?
How?
because it amplifies speech as well as collects it (1-3 khz X up to 100 fold)
via passive resonant properties
What part of your ear helps localize sound in the vertical axis?
the external ear
Explain how sound flows from outside the ear to the ovale window
the tympanic membrane will vibrate which is connected to the malleus. The malleus will transmit this vibration to the incus which will send it to the stapes which is attached to the ovale window.
Where is the vestibular nerve?
superior to the cochlea
Where does the external ear get sensory innervation?
from CN 5 (auriculotemporal) the cervical plexus (ventral rami spinal nerves i.e. lesser occipital and greater auricular) and small auricular branch of vagus to external tympanic membrane AND a small branch from CN 7
Where does the small auricular branch from the vagus go?
to the tympanic membrane
Where does the lesser occipital nerve and great auricular nerve come from? And what do they do?
the cervical plexus
they give cutaneous innervation to the external ear
What comes off of the vagus to give innervation to the external tympanic membrane?
the small auricular branch
How does the middle air maintain air in this cavity?
it has a connection to the outside world called the auditory tube.
What happens if you close the auditory tube?
your tympanic membrane will get sucked in and the middle ear will fill with fluid.
What is the point of the ossicles?
to create a mechanical advantage to allow for a slight movement of the malleus to cause a greater diversion of the stapes.
What is a second mechanical advantage that the ear has to transmit signals from the external ear into the inner ear?
The tympanic membrane is larger than the oval window
The oval window houses what kind of interface? So why is this significant?
a liquid interface
This is why we have mechanical advantages in the ear because we need to compensate for the loss of sound crossing the air/liquid interface
What is between each ossicle?
mini cartilaginous joints
What is the purpose of the middle ear?
amplifies sound signals, makes up for energy that is lost as sound moves from air into a liquid medium
What are the important amplification features of the middle ear?
size difference b/w tympanic membrane and oval window
mechanical advantage of bony lever system
Where the entrance to the mastoid antrum?
superior to the ossicles in the middle ear
Where is the round window?
inferior to the ossicles in the middle ear
What are the 2 muscles that help to reduce sound intensities by increase the stiffness of the apparatus?
stapedius muscle
tensor tympani
What does the tendon of the tenor tympani muscle connect to?
the malleus
where does the tensor tympani arise from?
the lateral membranous wall of the auditory tube.
How does the stapedius and tensor tympani reduce sound intensity?
they increase the tension on the tympanic membrane which limits the reflection and reduces the amount of sound
What cranial nerve innervates the tensor tympani?
V3
Will damage to he 7th nerve cause with hearing?
Leads to loss of differentiation b/w background noise and focused noise
What is the middle ear cavity continuous with?
mastsoid air cells
nasopharynx via auditory tube
How does the chordi tympani pass through the ear?
in the middle ear it crosses superior to the tensort tympani and inferior the malleus and incus joint
How does the facial nerve pass through the middle ear?
Over the stapes and medial to the lesser petrosal nerve
Where do you find the tympanic plexus?
on the cochlear prominatory
Explain how the tympanic nerve (branch of CN 9) gets through the middle ear
it goes into middle ear and forms the tympanic plexus on the cochlear promanatory and then ascends to form the lesser petrosal nerve, which go into the skull and exit at the formane ovale
Explain the pathway of CN 7 through the middle ear
CN7 is surrrounded by bone and continues down into the stapes and then just prior to leaving the sytoloid mastoid foramen, gives of the chordi tympani and goes over the malleus and under the incus and leaves via the petrotympanic fissure.
How does cranial nerve 9 exit the skull
through the jugular foramen
What does CN 7 do in the ear?
contributes a small sensory branch to the middle ear
What does the greater petrosal nerve do?
give preganglionic parasympathetics to lacrimal gland
Most of CN 7 passes through the (blank) at the (blank) ganglion. Then it leaves through the (blank)
semicanal of the facial nerve
geniculate
styloid mastoid foramen
Where is the malleus attached to the tympanic membrane?
on the medial side
What will be tympani membrane be like if there is an infection in the middle ear?
vibration of membrane is reduced,it appears red and a fluid level may be visible
Is it common to get infections of the middle ear?
yes
How do microorganisms enter the middle ear?
via the auditory tube
What kind of people are most susceptible to otitis media (middle ear infection)?
children with auditory tubes that are angled slilghtly superiorly towards the nasal cavity
What does this describe:
middle ear fills with fluid and tympanic membrane gets red and inflammed
otitis media
When you have a lot of water in your middle ear cavity, what kind of frequencies are preferred?
low frequency
If you have increased stiffness of the tympanic membrane (bulging of tympanic membrane) they what kind of frequencies are favored?
high frequency
Movement of the (blank) against the oval window causes vibration of fluid in the inner ear.
stapes
When the stapes gives movement to the oval window, how does the movement get further transferred into the inner ear?
sensory cells in the cochlea responds providing us with hearing :)
How do we get sympathetics into the middle ear cavity?
via the carotid plexus
What allows us to respond to movements of the head and provide balance?
sensory cells in the vestibular apparatus (part of inner ear)
What 2 kinds of lymph are found in the inner ear and where do you find them?
endolymph (scala media) and perilymph (scala vestibule and scala tympani)
What ion is found in high concentrations in the endolymph? Where do you find endolymph?
potassium scala media (cochlear duct)
What ion is found in high concentration in the perilymph?
sodium (a lot like plasma)
What kind of relationship does the ovale and round window have? please explain
recipricol
When the stapes pushes on ovale window, the pressure inside causes the round window to bulge out
The scale of vestibule is associated with what window?
Ovale (rememner oVale Vestibule)
What window is the scale of tympani associated with?
the Round window :)
So the middle ear is (blank) filled while the inner ear is (blank) filled
air
fluid
What is the apparatus for hearing?
cochlea
What is the apparatus for balance?
semicircular canal, utricle and saccule
where is the scala tympani connected to the scala vestibuli?
at the helicotrema
As a pressure wave hits the oval window and then is carried through the scala vestibule and scala tympani, it will create a pressure wave on the (blank)
scala media
The frequency of the sound that is created in the pressure wave will change depending on where you cause vibration/pressure wave along the (blank)
scala media
The scala media will vibrate at different points for different (blank)
frequencies
There is a (blank) representation of the scala media that musc be maintained all the way to the brain.
tonotopic
What nerve is going into the cochlea and what is it called?
CN 8, acoustocholear nerve
There are a group of ganglion cells called the (blank) that are picking up fibers from the cohlea.
spiral ganglion
The scala media has (blank) sitting on the basalar membrane.
Hair cells
The basal portion of hair cells are subject to (blank) . The apical portion of the cell is subject to (blank). What does this result in?
perilymph
endolymph
Creates potential difference between the cells
The hair cells have tight junctions that do what?
separate basal from apical parts of the cell.
The spuperior aspect of the scala media has a membrane called (blank)
reisners membrane (AKA vestibular membrane)
What innervates the basilar membrane ?
CN 8
There are 2 types of hair cells what are they?
the outer and inner :)
There is a gelatinous structure that sits off side of cochlear membrane and touches hair cells called the (blank)
tectorial membrane
Hair cells have cilia that have (blank) on it. Hair cell cilia contact (blank) membrane.
stereocilia
tectorial
Which are more prevalent, outer hair cells or inner hair cells?
outer hair cells
Which hair cells respond to diff. frequencies because they are position on the basilar membrane?
inner hair cells
If a hair cell is towards the base of the basilar membrane, then it will respond to (blank) frequencies. If situated near the apex of the basilar membrane then it will respond to (blank) frequencies.
high
low
The positions of hair cells on the basilar membrane responds to different (blank). When the basilar membrane vibrates, the hair cells fire.
frequencies
What about the basilar membrane determines frequency besides the hair cells?
the stiffness
Which part of the basiliar membrane is narrow? which is wide?
base,
apex
Greater the stiffness, the (blank) frequency
higher
What do the outer hair cells do?
change the tuning properties of the basilar membrane by pulling on the tectorial mmbrane (they are contractile and have efferent fibers on them)
CN 8 has both afferent and efferent fibers thus the efferent fibers of CN 8 innervate the (Blank).
outer hair cells
(blank) play a role in tiintus?
outer hair cells
How does CN 7 enter the ear?
at the internal auditory meatus
What does CN 7 form at the geniculate ganglion?
T
What does the greater petrosal nerve come off of and how does it travel?
it comes off of CN 7 and passes anteromedially and travels along side the lesser petrosal nerve on the floor of the middle cranial fossa and then passes over foramen lucerum and enters the pterygoid canal through the ptergoid palantine fossa.
How does the main trunk of CN 7 travel?
passes posterolaterally into the facial canal
As CN 7 descends toward the stylomastoid foramen it gives off what 2 things?
Chorda tympani
N. to stapedius
What 2 nerves go into the internal auditory meatus?
CN 7 and 8
How does CN 8 travel once it enters the internal auditory meatus?
it goes into the petros portion of temporal bone where it splits into a cochlear and vestibular portion.
What 2 ganglion are present in the inner ear?
vestibular ganglion and cochlear ganglion
What are the only 2 fibers that CN 7 doesnt carry?
SSA
General Somatic Efferents
What carry sympathetics to the pterygopalatine ganglia?
deep petrosal
What arches over CN 6?
CN 7
What is the only visceral sensory of the pons?
solitarious (does taste)
Describe the path of CN 8?
enters the internal auditory meatus, branches to the vestibular and cochlear branches.
Where are the special somatosensory cell bodies of CN 8 and where will you find them?
vestibular and spiral ganglia
Level 4 medulla
where do general somatic afferents go?
to the trigeminal nucleus (mesencephalic, chief sensory, spinal 5)
So what splits the dorsal and ventral cochlear nuclei (SSA nuclei)?
inferior cerebellar peduncle
What are 2 components of CN 9 associated with the middle ear?
GSA for the mucosal lining and GVE for the innervation of the parotid gland
CN 9 carrys GSA fibers to the middle ear that end where?
Spinal V
CN 9 carrys GVE (from inf. salivatory nuc.) to the parotid gland via what 2 nerves?
the lesser petrosal
auriculotemporal
Tell me about sinusoidal waves and the auditory system
the auditory system is designed to pick up both sides of the sinusoidal wave
For human hearing, sound is expressed in terms of (blank) and (Blank)
amplitude (intensity) and wavelength (frequency)
Speech and pure tone have very different (blank)
patterns
Is the auditory nerve superior or inferior to the vestibular nerve?
inferior
Does the vestibular nerve enter the semicircular canals?
yes
Explain the position of the tectorial membrane?
it is touching the scala vestibuli and is wihtin the scala media where it touches the hair cells
What does the spiral ganglion connect to?
basilar membrane
What all is between the scala media and the scala tympani?
the basilar membrane
the hair cells
(blank) receive efferents and modulate the stiffness of the tectorial membrane by some contractile property.
Outer hair cells
(blank) cells are for frequency recognition.
inner hair cells
What kind of axons go to outer hair cells?
efferent axons
What kind of axon go to inner hair cells?
afferent axons
What kind of axons go through the tunnel of corti?
efferent axons
Hair cells have many (blank) which sheer under the influence of the tectorial membrane.
stereocilia
What is kinocilium?
the tallest stereocilia that all the other stereocilia move towards
If your stereocilia is moving towards the kinocilium what will this cause?
If your stereocilia is moving away from the kinocilium?
depolarization
hyperpolarization
(blank) displacement is threshold of hearing- can convert mechanical displacement into electrical signal in 10 microseconds
.3nm
The air cells transmit signals (depolarize and such) via what king of channels?
mechanically gated channels.
How is each cilia of the hair cell connected?
via elastic springs that are mechanically gated channesl that open/close depending on kinocilum.
What is the ion of importance in the hair cell?
Calcium
What are compartment potential differences important for?
to prevent fatigue during prolonged stimulation
The ionic potential created in the inner ear is maintained by the (blank). How does it do this?
stria vascularis
it has potassium pumps in it :)
The potential difference in the inner ear is created by what 2 compartments?
scala media
scala tympani
What is the membrane potential of endolymph?
of perilymph?
Inner hair cells?
80mV
0 mV
-45 mv
Why does gentamycin and other ototoxic drugs do and some antibiotics do?
permanently damage hair cells AND mess up the stria vascularis so you dont have potassium pumping in
do we regenerate hair cells?
no
Staggered pivot points between the tectorial and the basilar membrane exaggerates the amount of displacement of the (blank) as the basilar membrane is displaced.
stereocilia
When the basilar membrane is in the upward phase which way are the stereocilia bending?
to the right (sound induced vibration)
When the basilar membrane is in the downward phase, which way are the stereocilia bending?
left
Inner hair cells respond to different frequencies depending on their (blank) on the basilar membrane (place principle).
location
The basilar membrane is tuned to different frequencies, this is called the (blank) phenomenon.
stiffness
The basilar membrane is tuned and when a traveling wave moves along the membrane it causes maximal displacement at different points depending on the (blank)
frequency
How does the tuning property of the outer hair cells work?
it dampens excess responses
What does the cochlea have that allows for frequency detection?
tonotopic organization of basilar membrane
What is the place principal?
a single auditory nerve fiber responds to a specific frequency because of the position of a hair cell along the basilar membrane
What is the time principal
that auditory nerve fibers lock in to a specific point along the sine wave “called phase locking or “volley theory”
(fibers come together as a group)
What is the labeled line mechanism?
nerve fibers are conditioned to elicit a specific response even if it didnt hear that frequency, it still thinks it heard it
A sound frequency of less than 1000 Hz gives you what kind of signal and how?
an accurate one by stimulating a single auditory fiber that can keep up with the frequency
A sound frequency b/w 1000 Hz and 4000 Hz gives you what kind of signal and how?
an accurate one by phase locking which means a bunch of fibers are coming together to make the wave
A sound frequency greater than 4000 hz gives you what kind of signal and how?
NOT accurate
by indiviual fiber responding at different places resulting in labeled line mechanism
What are cochlear implants made up of? How do they work?
electrode arrays
you have it jump through the round window and swirl around in the cochlea
Where does the auditory nerve attach?
to the cochlea
Explain the auditory pathway
auditory info comes in from auditory nerve and goes to the dorsal and ventral cochlear nuclei. *cochlear nuclei is the first OBLIGATORY nucleus Bilateral representation->goes to superior olive-> which goes to the lateral lemniscus -> inferior colliculus (OBLIGATORY NUCLEUS)-> medial geniculate complex of the thalamus (OBLIGATORY)-> primary auditory cortex
What does the inferior colliculus give you?
spatial map of position of sound
Where does bilateral representation of the auditory pathway occur?
at the cochlear nuclei
Where does crossing occur of the auditory pathway?
trapezoid body and after inferior colliculus
Multiple crossing sites yield bilateral representation so the only place where you can have one sided deafness is from a lesion to the (blank).
cochlear nuclei or anything peripheral to them.
If you get a lesion or deficit past the cochlear nucleithen what kind of damage will you get to your auditory system?
subtle differences in ability to discriminate sound typically the inability to recognize the localization of sound in space
Auditory pathways preserve (blank) along the way and they stop at many stations through the brainstem and various forms of (blank) occur at all the nuclei.
tonotopy
processing
What are the 2 nuclei that are involved in localizing sound on the horizontal axis?
MSO and LSO
What is the relay nucleus at the thalamus for audition?
the medial geniculate
What are 2 major cues used by listeners for locating the direction of a sound on the horizontal plane?
interaural time differece
interaural intensity difference
Is space mapped on auditory receptors? So how do we do this?
no
time differences are coded by MSO for frequencies below 3000 Hz
Intensity differences are coded by the LSO for frequencies above 3000 Hz
Time differences are coded by the MSO for frequencies below (blank)
Intensity differences are coded by the LSO for frequencies above (blank)
3000 hz
3000 hz
Will a lesion to the cortex cause deafness in one side?
no
(blank) of the thalamus relays info to the primary auditory cortex via the sublenticular part of the internal capsule
Medial geniculate nucleus
Medial geniculate nucleus of thalamus relays info to the primary auditory cortex via the (blank) part of the (blank)
sublenticular
internal capsule
In the medial geniculate nucleus, tonotopy is preserved as is (blank)
bilateral representation
How do you get nerve deafness?
damage to cochlea, 8th nerve or the auditory pathway
(blank) is gradual hearing loss in both ears that commonly occurs as people age.
Presbycusis
Why do aminoglycoside antibiotics and gentamycin suck?
cuz they are ototoxic
What will damage to the components of the outer or middle ear cause?
conduction issues
What is an acoustic neuroma?
8th nerve tumor
What is otitis media?
inflammation of middle ear cavity
What is otosclerosis?
ossicles lose joint cavity and fuse so they wont move properly and it will result in inhibition of oval window movement
What test does this:
distinguishes nerve from conduction deafness
Place tuning fork on forehead; where should sound be
heard the loudest
weber test
What test does this:
compares air conduction to bone conduction
Tuning fork on mastoid process, after it can no longer be
heard, place it next to ear and they should hear it again because air conduction is better than bone conduction.
Rinne test
When you put tuning fork on your head and you have nerve deafness, it will localize to (blank) ear.
good
When you put tuningfork on your head and you have a conduction problem, the sound will localize to (blank) ear
bad
When you have an acoustic neuroma, what nerves does it affect? What does it first present as?
5,6,7,8,9,10
titinus and then vertigo (cuz of 8th). Problems with eye movements (6th CN)
What are the expected findings of the weber test?
no lateralization but will lateral to ear if you occlude it
What will you find if you have conductive hearing loss during the weber test?
lateralization of affected ear
What will you find if you have sensorineural hearing loss during the weber test?
lateralization to better ear if affected
What is the expected finding in the RInne test?
air conduction hear longer than bone conduction by 2: 1 ration (Rinne positive)
What will you find if you have conductive hearing loss during the Rinne test?
bone conduction heard longer than air conduction in affected ear (rinne negative)
What will you have if you have sensorineural hearing loss during the Rinne test?
air conduction heard longer than bone conduction in affected ear,but less than 2:1
