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Auditory Vestibular System

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abisnail's version from 2017-05-22 16:09

Section

Question Answer
Name the components of the conductive hearing systemOuter ear, inner ear
Name the components of the sensorineural hearing systemInner ear, neural pathway, cochlear and retrocochlear
What is the pinna made of?Cartilage
Name the parts of the pinnaHelix, lobe, triages, anti helix, concha
What does the pinna do?Collects sounds
What is another name for the ear canal?External auditory meatus
What is the EAM made of?1/3 cartilage, 2/3 bone (temporal)
What is another name for ear wax?Cerumen
Where is ear wax made?The outer 1/3 of the EAM
Describe ear waxSlightly acidic, limits growth of bacteria and fungi, water-soluble
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Section

Question Answer
Where is the middle ear cavity?In the temporal bone
What lines the middle ear cavity?Mucous membrane
What is the upper half of the middle ear cavity called?Epitympanic recess or attic
What is the aditus?The posterior wall of the attic connecting to mastoid air cells
Name the windows on the medial labyrinthine wallOval connecting to the stapes and round
What is the structure between the 2 windows on the medial labyrinthine wall?Promontary
Where is the facial nerve?Above the oval window
What is the structure above the facial nerve?Lateral, horizontal semicircular canal
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Section

Question Answer
Where is the eustachian tube?Between the middle cavity and the back of the throat
Where does the eustachian tube open in the middle ear cavity?It opens into the anterior wall
Describe the angle of the eustachian tube45 degrees down in an adult, horizontal in a child
What is the eustachian made of?1/3 bone and 2/3 cartilage
How is the eustachian tube opened?By the elevator and tensor veli palatini
When does the eustachian tube open?Yawning, chewing, swallowing and talking
How is the entrance to the eustachian tube protected?Closure of the velum
What is the purpose of the eustachian tube?To ensure that you have the same pressure on either side of the tympanic membrane
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Section

Question Answer
Describe the tympanic membraneTransparent, pearly grey, shiny
Name the three layers of the tympanic membraneEpithelium, middle layer, inner mucous membrane
Describe the structure of the epitheliumThe epithelium is continuous with the EAM wall
Describe the structure of the middle layerThe middle layer has radial and circular fibres (pars tensa) and the superior pars flaccida acts as a pressure release
Describe the structure of the inner mucous membraneThe inner mucous membrane is continuous with the lining of the middle ear
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Section

Question Answer
Name the ossiclesMalleus, incus and stapes
How are the ossicles suspended?By lateral, anterior, superior and posterior ligaments and tendons
How big is the malleus?9mm
How big is the incus?7mm
How big is the stapes?3.5mm
Where is the head of the malleus?Malleoincudal joint
Where is the handle of the malleus?Attached to the tympanic membrane
Where is the body of the incus?Malleoincudal joint
What creates the incudostapedial joint?The lenticular process of the incus and the head of the stapes
Where is the malleoincudal joint?In the epitympanic recess or attic
Where is the footplate of the stapes?In the oval window
How is the footplate of the stapes held in place?The annular ligament
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Section

Question Answer
What does the tensor tympani do?Pulls the malleus neck anteromedially
Which CN is the tensor tympani innervated by?Vagus X
What makes the stapedius contract?Loud sound (80-85dB)
What happens when the stapedius contracts?Low frequencies are suppressed
Describe the protective function of the stapediusTenses the ossiclar chain to slow down vibration
Which CN innervates the stapdius?A branch of CN Facial VII
Describe the function of the acoustic reflex arcProtective but slow to react and the muscle gets tired quickly
Which CN innervates the acoustic reflex arc?Vestibulocochlear VIII
Describe the acoustic reflex arcSensory information transmits from the vestibulocochlear VIII to the ventral cochlear nucleus, then to the superior olivary complex. It also crosses to the SOC contralaterally.
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Section

Question Answer
Describe the labyrinth of the inner earBony (inside) and membranous
What is the name of the entrance to the labyrinth?Vestibule
Name two inner ear fluidsPerilymph and endolymph
Describe the perilymphHigh sodium and calcium, low potassium
Describe the endolymphLow sodium and calcium, high potassium
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Section

Question Answer
Where is the saccule?Continuous with the cochlea
What does the saccule do?Responds to vertical stimulation (gravity)
Where is the utricle?Continuous with the semi-circular canal
What does the utricle do?Responds to horizontal stimulation (acceleration and deceleration)
What is the macula?Receptor end organ
Cilia on the macula are embedded in theOtolithic membrane
What are otoconia?Crystals on the otolithic membrane that provide inertia, drag on hair cells
What synapse occurs at the macula?Synapse with vestibular part of vestibulocochlear VIII
What does movement of macula hair cells do?Provides information on movement, passing an action potential to the vestibular part of the Vestibulocochlear VIII
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Section

Question Answer
Describe the planes of the semicircular canals3 planes, perpendicular (at right angles) to each other
What is the purpose of the semicircular canals?They determine the position in space by responding to angular head motion
How do the semicircular canals connect to the vestibule?By the ampullae (bulb)
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Section

Question Answer
Describe the peripheral vestibular systemThe vestibular nerve goes through the internal auditory canal to the pons/medulla where it transitions to the central vestibular system
Where is the central vestibular system?The cerebellum
What is integrated by the central vestibular system?The vestibular, somatosensory and visual input
What does the central vestibular system do?Permits correct adjustments and balance
How is the central vestibular system involved in balance?The vestibular uses the saccule, the somatosensory uses muscle tone and pressure sensation and the visual input uses external reference
Which reflex stabilises vision during head movement?Vestibulo-ocular reflex
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Section

Question Answer
Describe the cochleaA 25-35mm long snail like tunnel in the temporal bone, pointing towards the cheekbone that makes two and a half turns around the modulus
What is the modiolus?The central core of the cochlea where nerves congregate and leave as the vestibulocochlear nerve VIII
Name the three channels of the cochleaScala vestibuli, scala tympani and scala media
Which channel(s) are filled with perilymph?Scala vestibuli and scala tympani
Which channel(s) are filled with endolymph?Scala media
Where is the scala vestibuli?From the oval window to the helicotrema
Where is the scala tympani?From the helicotrema to the round window
Where is the scala media?Between the scala vestibuli and the scala tympani
Name the structures in the vestibular aqueductEndolymphatic duct and sac
Where is the cochlear aqueduct?Leaves the scala tympani near the round window ending in the subarachnoid space of the brain
What does the cochlear aqueduct do?It may permit transfer of perilymph to CSF
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Section

Question Answer
Reissner's membrane is the _____ partition of the scala mediaUpper
Basilar membrane is the ______ partition of the scala mediaLower
Where is the basilar membrane?From the spiral lamina to the spiral ligament
Where is the stria vascularis?On the lateral wall between Reissner's and basilar membranes
What does the stria vascularis do?May maintain the balance of potassium ions in the endolymph
Where does the organ of Corti sit?On the basilar membrane
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Section

Question Answer
What does the inner and out pillars of Corti do?Support
How many rows of inner hair cells are there?1
How many rows of outer hair cells are there?3
Which hair cells are embedded in the tectorial membrane?Outer hair cells
What is the spiral limbus?An attachment for the tectorial membrane
What do Dieter's cells do?They support the base of OHCs
What do Hensen's cells do?Support OHCs and free the edge of the tectorial membrane
The ____ membrane is tunedBasilar
How do you change pitch detection?Changing the level of stretch of the basilar membrane
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Section

Question Answer
OHCs are ______ at the base of the cochleaShorter (higher frequency)
OHCs are ______ at the apexLonger (floppy, lower mass - lower frequency)
Stereocilia are _____ and more numerous at the baseShorter
OHCs are structured like _____Muscles
How can OHCs change shape?Shorten or lengthen when stimulated or inhibited
How are IHCs stimulated?By endolymph flow in the space between IHC and tectorial membrane
Which is the most important part for code frequencies?IHC stimulation
What sound pressure levels do IHCs respond to?Above 40dB
How are OHCs stimulated?By tectorial membrane 'shearing'
At the point of stimulation, the tectorial membrane _______Tightens
What happens when the OHCs are stimulated?Endolymph flow is constricted which causes turbulence and IHC stimulation. It is a cochlear amplifier
How are OHCs damaged? Noise/chemical related hearing loss
What does damage of OHCs mean for hearing?Inability to separate 2 sounds/frequencies as it effects frequency resolution
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Section

Question Answer
What do cochlea hair cells do?Transform mechanical energy into neural impulses
What is the endolymph resting potential?+80mV
What is the inner hair cells resting potential?-40mV
What is the outer hair cells resting potential?-70mV
What happens when K+ flows into the hair cells?The cell is depolarised which opens calcium channels in the cell wall, Ca+ flows in (hyper polarised) and triggers the neurotransmitter release and K+ flows out
What does a neurotransmitter release trigger?Action potential
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Section

Question Answer
Action potential in the cochlea travel to the _____Spiral ganglion
What percentage of afferent information is provided by IHCs?95%
What percentage of afferent information is provided by OHCs?5%
How many ganglion cells do each IHC connect with?10-18
How many OHCs are branched from each nerve?10-50
Nerves exit from the modulus as _____Vestibulocochlear VIII
_____ fibres twist around _____ fibresBasilar - apex
Basilar fibres are ____ frequencyHigh
Apex fibres are ____ frequencyLow
After CN VIII joins CN VII, it travels through theInternal auditory canal
What is an acoustic neuroma?Benign growth in internal auditory canal can press of the nerve and cause symptoms
What can an acoustic neuroma in the IAC affect?Hearing, balance and face
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Section

Question Answer
What role does the middle ear play in auditory acoustics?Impedance matching device (27-30dB)
What is impedance?The ability to transport air to fluid
What does the middle ear do?Take weak airborne signals, amp the up to stronger fluid borne to be strong enough to move structures on basilar membrane and organ of Corti
What part do the middle ear muscles play in auditory acoustics?Protection (slow and quick to tire) and suppression of physiological noise
How do they middle ear muscles perform their function?The acoustic reflex stiffens the ossicular chain at ±85dB
What part does the eustachian tube play in auditory acoustics?Ventilation of middle ear cavity
What happens if the eustachian tube is blocked?There is negative middle ear pressure, it fills with fluid and causes the middle ear system to be stiff
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Section

Question Answer
Where are high frequencies detected on the basilar membrane?The basal turn as it is stiffer and has less mass
Where are low frequencies detected on the basilar membrane?The apical turn as it is less stiff and has more mass
How is tuning of the basilar membrane refined?By the OHCs
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Section

Question Answer
What is tonotopic organisation?Responding to different frequencies along a length
There is ______ processing of signals as they move up the pathwayIncreasing
What is processed at the inferior colliculi?Interaural time/intensity differences
What is binaural representation of sound?Sounds heard in R/L are arriving in both lobes to be ablate process signals
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