Unit3_Audio&Vestibular&Otology Flashcards
___?___: series of pressure waves of alternating compression (increased density) and rarefaction (decreased density) of air molecules
Sound
Intensity: increase of intensity in a sound is when the air is compressed more forcefully during peak compression each cycle → _______ density of air
increased density
pressure at peak of compression = ?
“Loudness”
Sound above ___dB → permanent hearing loss
120dB
What makes up the External Ear?
- Pinna
- External auditory meatus
- ends at the tympanic membrane
Pressure waves then moves tympanic membrane.
___1___ → TM bulges out
___2___ → TM presses in
- Rarefaction
2. Compression
What makes up the Middle ear?
The ossicles
- Malleus
- Incus
- Stapes
How are the ossicles of the middle ear moved?
Via the movement of the Tympanic Membrane
Acoustic impedance mismatch: Air-fluid boundary causes most acoustic energy to be reflected away,:
water → __1__ impedance
air → __2__ impedance
water → HIGH impedance
air → LOW impedance
How does the middle ear and ossicles allow us to overcome the 30dB loss to impedance mismatch?
- area of the TM is 20x greater than that of the stapes. This amplifies any vibration at the TM.
- Ossicle oreintation → levering action = LARGER force.
Damage to or loss of hair cells and/or nerve fibers is known as __________ hearing loss
Sensorineural hearing loss: damage to or loss of hair cells and/or nerve fibers
Degradation of mechanical transmission of sound engery in the middle ear is known as __________ hearing loss.
Conductive hearing loss: degraded mechanical transmission of sound energy through middle ear.
What are the common causes of Sensorineural hearing loss?
1) Excessively loud sounds
2) Exposure to ototoxic drugs (diuretics, aminoglycoside antibiotics, ASA, cancer therapy drugs)
3) Age (presbycusis) - lose high frequency hearing, as we age
What are the common causes of conductive hearing loss?
1) Filling of middle ear with fluid during otitis media
2) Otosclerosis - arthritic bone growth impedes ossicle movement
3) Malformation of ear canal (swimmer’s ear, cauliflower ear)
4) Perforation/rupture of tympanic membrane
5) Interruptions of ossicular chain
6) Static pressure in middle
How can you differentiate conductive vs. sensorineural hearing loss?
Can overcome conductive hearing loss by placing tuning fork against bone
BM more flexible, wider, and thicker at apex → ___FREQUENCY VIBRATION
APEX = LOW FREQUENCY VIBRATION
BM thinner narrower, and more rigid near oval and round window at base of cochlea
→ ___ FREQUENCY VIBRATION
BASE = HIGH FREQUENCY VIBRATION
What are the three compartments of the Cochlea?
scala vestibuli, scala media, scala tympani
What sits on top of the BM and in the scala media?
Organ of Corti
What seperates the scala media and the scala tympani?
Basilar Membrane (BM)
Mechanical properties of BM key for discrimination of sound frequency.
_________: hole in BM at apex of cochlea, connects scala tympani to scala vestibuli, relieves pressure → both have perilymph
Helicotrema
Describes the process by which sound elicits movements of the BM.
Stapes hits oval window (during peak of compression) → oval window bulges into scala vestibuli = “traveling wave” - reaches max amplitude at certain location along length of BM.
Particles itself are NOT traveling with wave, just going up and down → downward movement of BM to relieve compressio → compress fluid in scala tympani → round window bulges out towards middle ear (pressure relief)
Opposite happens with rarefaction - round bulges in, oval bulges out
_____________ : sensory receptor responsible for detecting sound pressure and converting mechanical vibration into a membrane potential change (transduction)
Inner hair cell (IHC)
Where are stereocilia located on the inner hair cells?
Apical surface of IHC
Pushing stereocilia bundle in direction toward longest stereocilia (Kinocilla) does what?
Depolarization
Pushing stereocilia bundle in direction toward the shortest stereocilia does what?
Hyper-polarization
creasing a potential of 130mV, resulting in an end potential of +80mV (from the resting potential of -50mV)
What is the fluid that is K+ rich that fills the scala media and bathes stereo cilia on the APICAL side of the hair cells called?
Endolymph
What is the function of Stria Vascularis?
actively pumps K+ into the endolymph to maintain a high [K+] → creating endocochlear potential
MUTATION in gap junction subunit, connexin 32 → collapse of endocochlear potential, congenital deafness is associated with what?
Stria Vascularis
What is perilymph?
ionic composition similar to blood (high Na, low K+), fills scala vestibuli and scala tympani
ionic composition similar to blood (high Na, low K+), fills scala vestibuli and scala tympani is known as what?
perilymph
What connects the apex of stereocilla to the next adjacent taller stereocilla and plays a key role in the opening and closing of mechanically gated channels at the tips of stereocilla?
Tip-links
The following describes what?
- Generates shearing force (between basilar and tectorial membrane) that results in bending of hair cells.
- Directly attached to outer hair cells.
Tectorial membrane
Auditory nerve fibers: ______ fibers located at basal end of hair cells
Auditory nerve fibers: AFFERENT fibers located at basal end of hair cells
Auditory nerve fibers: afferent fibers located at ______ end of hair cells
Auditory nerve fibers: afferent fibers located at BASAL end of hair cells
Auditory nerve fibers: afferent fibers located at basal end of hair cells.
Cell bodies in ______1______.
Projects to _____2______ of brainstem.
- spiral ganglion
2. cochlear nucleus
From the hair cells, how are APs generated and sent to the second order neurons in the brainstem?
Hair cell depolarizes → open Ca2+ basolateral channels → synaptic vesicles release glutamate → excitation of afferent axon → AP sent to second order neurons in brainstem
What is the cochlear amplifier?
Efferent innervation from central auditory system act upon OHCs to amplify movements of BM.
Does the cochlear amplifier deal with IHC or OHC?
OCH - Outer Hair Cells
OHCs responding to changes in voltage with a change in length is a process called __________.
“Electromotile”
Voltage sensitive _________ protein → change length of OHC
Voltage sensitive PRESTIN protein → change length of OHC
With regards to the cochlear amplifier, → OHC pulls BM toward or away from tectorial membrane → changes mechanical frequency selectivity of BM
→ Contributes __?_dB of cochlea’s sensitivity to sound.
OHC _________ movement of BM in a frequency dependent manner.
50dB
enhances
What are Medial olivocochlear neurons (MOC)?
efferent neurons that innervate OHCs.
- senses contexts of sound env. and acts as feedback control of cochlear sensitivity (cochlear amplifier) and adjusts it to suit whether you are in a loud or quiet env.
Uses ACh.
Is sensorineural deafness due to damage of IHCs or OHCs?
OHCs.
OHCs are more sensitive to damage from ABX and loud sounds.
What is the pathophysiological process of the ototoxicity of ABX like streptomycin and gentamycin?
those ABX block transduction ch. of OHCs and can kill of OHCs = deafness
____________ Cells: aka auditory nerve (8th CN), innervates hair cells
Spiral Ganglion
Spiral Ganglion Cells: aka auditory nerve (8th CN), innervates hair cells.
Type I ANFs: innervate __1__, myelinated
Type II ANFs: innervate __2__, not myelinated
- IHCs
- OHCs
Type I ANFs: innervate IHC, myelinated
Make up 95% of ANFs
10-30 ANFs innervate a single IHC
Type II ANFs: innervate OHC, not myelinated
1 ANFs innervate 10 OHCs
Unilateral lesions _______ to cochlear nuclei do NOT produce unilateral deafness
ROSTRAL
_______ lesions and those including the CN produce unilateral deafness
CAUDAL
______________ = physical separation in space of ears → different times of arrival of sound at two ears
Interaural time differences (ITD)
______________ = ears separated by an obstacle (the head) → acoustic shadow for high frequencies
Interaural level differences (ILD)
Duplex theory of sound localization:
Low frequencies → __1__
High frequencies → __2__
- ITDs
2. ILDs
______________________ : arise from direction and frequency dependent reflection and diffraction of pressure waveforms of sounds by pinna that result in broadband spectral patterns, or shapes, that change with location
Spectral cues - Monaural spectral shape.
Spectral cues - Monaural spectral shape ~ primarily with ___ frequency sounds.
high frequency
ITDs encoded in ________________ - nucleus of superior olivary complex
Medial superior olive (MSO)
MSO contains input from CONTRALATERAL ear (already crossed in trapezoid body), so projects ___________ up to auditory midbrain
IPSILATERALLY
MSO contains input from ____________ ear (already crossed in trapezoid body), so projects IPSILATERALLY up to auditory midbrain
CONTRALATERAL
MSO receives excitatory input from both ears via cells of the what nucleus?
anteroventral cochlear nucleus (AVCN).
AVCN receive excitatory inputs from ANFs
AVCN organized tonotopically
1) Afferent input to MSO neurons from ANF/AVCN carry timing info via ___________ neural responses.
2) MSO neurons = ___________ (what type of detectors) → maximal response when AP from AVCN cells from L ear coincide with R ear.
3) Axons of AVCN cells input to MSO form delay lines due to differences in _________ (what?) from AVCN to MSO → differences in neural conduction times to MSO; Projection to contralateral MSO = longer path length than ipsilateral MSO
1) phase-locked
2) coincidence detectors
3) neural path length
All 3 → *Allows for a place code for the horizontal location of sounds in terms of timing between the two ears
ILDs encoded by the ______________ olive.
ILDs = Lateral superior olive (LSO)
Ipsilateral ear input to LSO conveyed via ANF synapses with AVCN cells → ___(which side?)___ LSO
ipsilateral LSO
Contralateral ear input to LSO conveyed from AVCN → across midline to neurons of ____1. what nucleus?___
AVCN synapse onto MNTB = ____2____= LARGEST synapse in entire CNS.
MNTB neurons = ____3____→ inhibitory effect on LSO
- medial nucleus of trapezoid body (MNTB)
- calyx of Held
- glycinergic
The net results of ILS encoded by the LSO is the ____1____ excitation and ____2____ inhibition of LSO neurons allowing computation of difference between intensity of sounds present at the two ears.
- ipsilateral excitation
2. contralateral inhibition
ILDs:
Spectral cues encoded in _____________ Nucleus → across midline to excitatory synapse on inferior colliculus.
Dorsal Cochlear Nucleus.
Lesion → can’t tell if sound is above or below you, but can still localize in horizontal plane.
Primary auditory cortex A1 = Brodmann’s area ?
Secondary auditory cortex A2 = Brodmann’s area ?
Primary auditory cortex A1 = Brodmann’s area 41
Secondary auditory cortex A2 = Brodmann’s area 42
Clinical importance: IC represents sound in contralateral hemisphere, and MSO, LSO and DCN reconverge at contralateral IC.
Unilateral lesions in IC or above → deficits in sound source localization for sources contralateral to lesion.
IC sends excitatory projections to ipsilateral thalamus medial geniculate body (MGB) → auditory cortical areas located in superior temporal gyrus
Clinical importance: IC represents sound in contralateral hemisphere, and MSO, LSO and DCN reconverge at contralateral IC.
Unilateral lesions in IC or above → deficits in sound source localization for sources contralateral to lesion.
IC sends excitatory projections to ipsilateral thalamus medial geniculate body (MGB) → auditory cortical areas located in superior temporal gyrus
What are the Otolith organs? (3)
- Utricle
- Saccule
- Sensory epithelia (Maculae)
Where is the Utricle and what is its function?
lies at floor of vestibule.
Senses position of head with respect to gravity.
Where is the Saccule and what is its function?
hangs vertically on lateral wall of vestibule.
Senses linear acceleration in vertical direction
Sensory epithelia (maculae): contains hair cells and supporting cells, with ____1____ surface overlaid with gelatinous mass knwon as what?
- apical
otolithic membrane
Sensory epithelia (maculae) has thousands of hair cells and otoconia (Calcium carbonate crystals) that lie over hair cells on sensory epithelia → assist with what function?
gravity detection, postural changes = “static” receptors
Hair cell axes of polarity are _________ in utricle and saccule.
OPPOSITE
Saccule hair bundles oriented facing AWAY from striola (Central region of epithelium) while utricle hair bundles face TOWARDS
→ maximum excitation (depolarized) of one group of hair cells, while opposing hair bundle orientations maximally inhibited (hyperpolarized)
What is the func. of Sensory epithelia (maculae)?
Function: Detect linear acceleration (change in velocity) of head and position with respect to gravity
What are the 3 semicircular canals?
horizontal, anterior, and posterior canals
Which 3 semicircular canals works in the following way?
the canals on L and R work together - while one is maximally stimulated the other is maximally inhibited.
Horizontal Canals
Which 3 semicircular canals works in the following way?
____1____ canal on one side works with ____2____ canal from other side
- Posterior
2. Anterior
The swelling at one end of each canal with specialized patch of epithelium, “crista” → contain sensory hair cells is called what?
Ampulla
Describe the functional process of the Ampulla.
Hair bundles project into cupula (gel-like substance).
Endolymph moves cupula and stimulates hair cells in the crista ampullaris → Firing rate will increase, and then adapt (due to endolymph inertia).
Hair bundles in a given crista all have kinocilia oriented the same way → when cupula deflected by endolymph during a movement of the head, all hair bundles in a given crista deflected the same way.
The tallest cilium within on one side of hair bundle is known as the what?
Kinocillium
What are tip links?
connect adjacent cilia, and their lower end to an ion channel
____1____ = high K+, low Na and Ca2+
____2____ = low K+, high Na and Ca2+
- Endolymph = high K+, low Na and Ca2+
2. Perilymph = low K+, high Na and Ca2+
during head rotation, vestibular system signals how fast head is moving and oculomotor system responds to keep visual field stable.
This reflex is known as what?
Vestibular Ocular Reflex (VOR)
In the VOR, eye movement will be in the ________ direction from the head rotation.
OPPOSITE
in VOR:
Move head left → endolymph moves in opposite direction to rotation → hair cells excited on ___1___, inhibited on ___2___. (which side)
- LEFT
2. RIGHT
In VOR:
1) Vestibular afferent fibers synapse in ________ nucleus.
2) _________ nerve innervates medial rectus on LEFT side (excite, contract).
3) At same time, get excitatory signal from LEFT horizontal canal via (what CN?) nerve to excite lateral rectus muscle on RIGHT eye
- vestibular
- Oculomotor
- CN6
Where is the Vestibular nuclei and what is its overall function?
Vestibular nuclei: located at border of caudal pons and rostral medulla, integrate vestibular signals with information from spinal cord, cerebellum, and visual system.
What are the 4 nuclei of the Vestibular nucleus?
- Superior Vestibular nucleus
- Medial Vestibular nucleus
- Desc/Inferior Vestibular nucleus
- Lateral Vestibular nucleus
_____which two?_____ Vestibular nuclei: receive fibers mostly from semicircular canals.
→ Gaze control
→ medial longitudinal fasciculus/medial vestibulospinal tract → oculomotor nuclei and cervical motor neurons of neck musculature
Coordinates eye and head movements
Superior and Medial Vestibular nucleus
Coordination of eye and head movements are the functions of what Vestibular Nuclei?
Superior and Medial Vestibular nucleus
_______________ Vestibular Nuclei:
Input from saccule, utricle, and semicircular canals, spine, and cerebellum
All projects to vermal cerebellum, reticular formation, and other brainstem centers
Descending/Inferior Vestibular nucleus
____________ Nuclei: input from canals and otoliths
Aka lateral vestibulospinal tract → excitation of extensor muscles of limbs, postural reflexes
Also gets input from spine and cerebellum
Lateral Vestibular nucleus
Utricles → lateral, medial, inferior vestibular nucleus.
Spine and cerebellum → lateral nucleus.
Semicircular canals → medial, superior vestibular nuclei.
Utricles → lateral, medial, inferior vestibular nucleus.
Spine and cerebellum → lateral nucleus.
Semicircular canals → medial, superior vestibular nuclei.
Second-order cells in different nuclei project to different regions of CNS, and some project directly to ____________ lobe of cerebellum
flocculo-nodular lobe
_______________ reflex helps maintaine head stability and upright stance of the head.
Vestibulo-collic reflex (VCR)
_______________ reflex assist balance and provide a framework for coordinated motion of the limbs during ambulation.
Vestibulospinal reflex (VSR)
when you don’t have to tell your arms and legs where to go to help your balance, and when you do fall down, this reflex helps to break your fall. d
Vestibularspinal Reflex (VSR)
What does a value of Zero indicate on an audiogram?
0 = normal hearing threshold of a young adult
The pt. should have good clarity at a decibel level adequate for patient. If not, what is likely wrong?
a neural hearing loss issue like schwannoma
_____________: gradual, progressive, bilateral hearing loss caused by degenerative physiologic changes associated with aging.
Presbycusis
- Decreased hearing threshold sensitivity.
- Decreased ability to understand suprathreshold speech.
- Central auditory process impairment.
Noise exposure that leads to noise trauma will result in an audiogram that looks like what?
What type of hearing loss is this?
Audiogram with have a sharp peak in the higher freq.
Noise truama ~ Sensory Hearing Loss
Name some common Ototoxic agents:
- aminoglycosides (gentamicin)
- loop diuretics
- cancer agents (cis-platinum)
- macrolides (erythromycin)
- ASA
- quinine
- hydrocodone
- viagra
What is Endolymphatic Hydrops
- expansion/distention of endolymphatic compartment of the inner.
- idiopathic and pathological with recurrent episodes of VERTIGO, sensorineural hearing loss, tinnitus, and aural fullness.
Disordered inner ear fluid homeostasis causes dysfunction in what?
Stria Vascularis; Vascular dysfunction and/or vasculitis.
- Systemic metabolic disorders: DM, hyperthyroidism, renal failure, arteriosclerosis.
- Immune system disorders: lupus, Cogan’s syndrome, sarcoidosis, Wegener’s granulomatosis, autoimmune inner ear disease
Endocochlear potential is the normal func. of what ear structure?
ORGAN OF CORTI
- Serves as driving force for ion movement in sensory transduction.
- Issue with pumping of K+ and EC ion conc.
Meniere’s Disease = aka?
Endolymphatic Hydrops: a swelling of the endolymphatic space~distention
a swelling of the endolymphatic space~distention = ?
Meniere’s Disease = Endolymphatic Hydrops
What is the Tx of sensorineural hearing loss?
• Air Conduction Hearing Aids • Implantable Hearing Aids • Cochlear Implants ○ Eclectically stim the ear ○ Indicated in peds after age 1.; Will allow them to dev normal speech and language. • Assistive Listening Devices •Speech and Language Training
How do you Tx a Vestibular Schwannoma?
Surgical Resection
Stereotactic Radiosurgery: a single dose drug that stops the tumor from growing.
Neurofibromatosis Type 2 (NF2) is ~ what hearling loss disease?
NF2 is a form of Vestibular Schwannoma.
the other form is sporadic.
What is a Cholesteatoma in the ear?
○ Skin cyst ~ Squamous epi ○ NOT CANCERS! ○ Erosive and espansile --> destructions of the bone of the middle ear. § Can spread to the base of skull. ○ Leads to chronically draining ears.
Is Cholesteatoma cancerous?
NO!!!
- __dB is normal hearing threshold.
* __ - __dB is conversational level.
- 25dB is normal hearing threshold.
* 50-60dB is conversational level.
