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93 Cards in this Set
- Front
- Back
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What does frequency measure?
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tone/pitch in Hz (cycles per second)
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What does intensity measure?
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loudness in decibles
measured by the amplitude of the wave |
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How are low frequency sounds detected?
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interaurally by time differences
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How are high frequency sounds detected?
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by interaural intensity differences
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Waht is the ftn of the external ear?
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Collection of sound
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What is the function of the middle ear?
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impedance matching and amplification of sound
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What is the function of the inner ear/
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transduction and signal analysis of sound
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What anatomy comprises the external ear?
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-pinna (auricle)
-external acoustic meatus -tympanic membrane |
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What anatomy comprises the middle ear?
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-malleus, incus, stapes
-tensor tympani, stapedius muscles -oval window -round window |
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What anatomy comprises the internal ear?
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-cochlea
-vestibular apparatus |
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How is the cochlea oriented and what is its main function?
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anteromediall and main ftn is for hearing
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What is the orientation and function of the vestibular apparatus?
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posterolateral
-balance is main function |
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What is the bony labyrinth?
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interconnected cavities and canals of the inner ear. Composed of the vestibule and cochlea
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Desctibe the " bone" components associated with the inner ear
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It is the petrous potion of the temporal bone-walls are denser than surrounding bone
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describe the vestibule of the bony labrynth
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it is the central chamber portion of the BL.
-opens to semicircular canals (posterior) -opens to cochlea (anterior) -oval window – in lateral wall |
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Describe the cochlea portion of the bony labrynth
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-shell-shaped (2 ¾ turns)
-diameter narrows from base to apex -perpendicular to petrous bone |
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What is the membranous labryinth?
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interconnected membranous sacs and ducts suspended within bony labyrinth
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What fluids surround the membranous labrynth? What fluid fills the membranous labrynth?
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Surrounded by perilymph
filled with endolymph |
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Describe the composition of endolymph
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-high K+, ionic composition similar
to intracellular fluid |
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What is the scala media?
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the cochlear duct
it iws wedge shaped and spirals around the modiolus |
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What is the modiolus?
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The central core of the cochela that is spongy bone that runs "up the middle" of the choclea in cross section
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What does the modiolus house?
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-contains spiral ganglion (cell bodies of primary sensory eurons
of auditory system) |
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Describe the neurons of the spiral ganclion
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-cell bodies of primary sensory neurons (bipolar neurons)
-axons in cochlear division of CN 8 -project into CNS (cochlear nuclei of medulla) |
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What are the 3 channels in the cochlea? What fluid fills them
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scala vestibuli -perilymph
scala media-endolymph scala tympani-perilymph In that order top->bottom) |
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What is the helicotrema?
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Where the scala vestibuli and scala tympani are continuous
with each other |
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What layer of the cochlea contains the oval window with
footplate (base) of stapes? |
oval window with
footplate (base) of stapes |
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What layer of the cochlea contains the round window?
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scala tympani
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What does the near modiolus contain?
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bony Spiral lamina (contains openings for cochlear nerve fibers) (wider at base)
and the Spiral Limbus (thicked periosteoum on spiral lamina |
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Where do the vestibular membrane (roof of scala media)
and tectorial membrane attach? |
To the spiral limbus (thickened periostium on spiral lamina of near modiolus)
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What structures does the opposite modiolus contain?
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Spiral ligament
stria vascularis |
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Where does the basilar membrane attach?
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the spiral ligament (which is on the far side of the scala media)
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What is the stria vascularis?
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it is found in the opposite modiolus and is at the
-surface of spiral ligament -pseudostratified epithelium -highly vascularized -maintains endolymph (ionic conc.) |
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Where is the basilar membrane
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between the spiral lamina and the spiral ligament; it seperates the scala media from the scala tympani.
the membrane is narrower at the base near the oval window where it is also stiffer |
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What is the place theory of cochlear tuning?
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the phenomenon that traveling waves any given sound frequency will produce maximum displacement at a specific place on the
basilar membrane |
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What is t he Organ of Corti?
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a sensory "apparatus" that restso n the basilar membraine. it is bathed in endolymph and has sensory receptors with hair cells
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What is the tectorial membrane?
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-gelatinous structure
-secreted by spiral limbus |
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Describe the hair cells of the Organ of Corti...
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The are mechanoreceptors with steriocilla (100 per hair cell) that contact the tectorial membrane.
There are inner and outer hair cells |
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Describe the stereocilia of the hair cells
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-microvilli
-arranged in rows of increasing height with tallest toward outer border -linked at tips |
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What are phalangeal (Dieter’s cells)?
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They are support cells for the I/O hair cells that send apical processes towards the endolymphatic space
They flatten near the apical ends to form the Apical Cuticular Plate |
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How are the stereocillia of the outer hair cells arranged?
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in a V shaped formation
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Describe the sensory transduction of the hair cells
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they are mechanically gted cation channesl that cause depolarization when deflected towards the tallest stereociilum and hypperpolarized when deflection is AWAY from the tallest ctereocilium
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What cation is entering the cell with depolarization of the hair cells?
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K+ is entering
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What kind of "potential" do the hari cells exhibit?
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biphasic, graded receptor potentials
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Where the perilymph is found and what its ionic composition is...
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-scala vestibuli, scala tympani
-continuous with subarachnoid space via cochlear duct -low K+; high Na+ |
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Where the endolymph is found and what its ionic composition is and what secretes it...
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-scala media
-secreted by stria vascularis -high K+; low Na+ |
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What is the diffusion barrier?
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tight junctions at apical surface of
hair cell that create separate extracellular ionic environments at apical and basal surfaces (Peri between, endo above) |
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What is the endolymphatic potential amoount?
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=80mV
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K+ influx of mechanically stimulated hair cells causes what phenomenum to occur? What is the result?
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depolarization of hair cell membrane is caused by K+ influx
-this causes opening of voltage-gated Ca2+ channels in hair cell soma -neurotransmitter release onto primary afferent fibers |
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Describe Type I afferent fibers of the cochlea.
(percentage, synapse) |
-The composes 90-95% of the spiral gangion cells
-one fiber synapses on 1-2 IHC, but each hair cell gets innervated by 20 type I fibers. |
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What is the frequency range like for type I fibers?
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responsive in a narrow frequency range
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Describe Type II afferent fibers of the cochlea.
(percentage, synapse) |
-5-10% of spiral ganglion cells
-synapse on many (>10) outer hair cells |
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About how many inner hair cells are there?
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3,500
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About how many outer hair cells are there?
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12,000 total OHCs
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What is the frequency range like for type II fibers?
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-sensitive to low frequency sounds
-responsive in a wide frequency range |
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What are the Response characteristics of type I fibers? (3)
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1) They have a characteristic frequency (that is designated as the lowest frequency that elicits a response)
2) the nerve continues to discharge a signal until the sound stops 3) the discharge rate is sigmoidally related to the intensity of the sound intensity |
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What is Neural coding of sound stimuli?
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1) certain positions of the fibers alng the cochelar spiral respond best to different frequencies
2)Intensity is coded by the AP/discharge rate and additioanl fibers are requited at higher intesities |
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What is the efferent innervation of the cochlea?
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olivocochlear fibers that modify basilar membrane function (cochlear amplification)
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Where do olivocochlear fibers arise from? Where do they travel?
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arise from medial and lateral superior olive. They travel to cochlea in vestibular division of CN VIII
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Where do the axons of the Lateral Superior Olive project to?
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ipsilateral type I fibers innervating Inner Hair Cells
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Where do the axons of the Mediall Superior Olive project to?
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project bilaterally to Outer hair cells
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What is the main function of the Inner hair Cells?
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-the act as sensory receptors for sound stimuli
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What is the main function of the Outer hair Cells?
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They change length when stimulated so that they alter the mechanics of the basilar membrane aiding in:
-cochlear amplification and -increases signal to noise ratio (cocktail party effect) |
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What are the two central audutory pathways?
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Monaural and binaural
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What is the path of the monaural pathway?
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-cochlear nuclei
-decussate in posterior acoustic stria -ascend in lateral lemniscus -inferior colliculus -brachium -medial geniculate nucleus -auditory radiations -primary auditory cortex |
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What is the path of the binaural pathway?
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-cochlear nuclei
-trapezoid body -superior olive -lateral lemniscus -inferior colliculus -commissure -brachium -medial geniculate nucleus -auditory radiations -primary auditory cortex |
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What is the tonotopic organization of the central auditory pathway?
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mapping of specific frequencies begins in cochlea and is
maintained throughout pathway Higher= more medial Lower=more lateral |
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where do afferent CN VIII fibers go?
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they bifricate and terminate in ipsilateral cochlear nuclei (anterior and posterior)
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Where do cochlear nuclei neurons project?
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to the inferior colliculus and superior olivary nucleus via parallel ascending pathways
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How is sound localized?
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by interaural time differences
anterior cochlear nucleus projects bilaterally to MSO -MSO neurons have medially and laterally directed dendrites; function as coincidence detectors |
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Where do -MSO neurons project?
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via I/L lateral lemniscus to the inferior colliculus
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Where are high frequency sounds localized?
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lateral superior olive
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Where does the LSO receive input from?
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-direct excitatory input from
I/Lanterior cochlear nucleus -indirect inhibitory input from C/Lanterior cochlear nucleus after a relay in medial nucleus of trapezoid body |
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Where do LSO axons project?
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project via I/L lateral lemniscus;
relay in nuclei of lateral lemniscus to C/L inferior colliculus |
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What determines the response of the LSO neuron?
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-balance of excitation (I/L ear)
and inhibition (C/L ear) |
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-LSO neurons are maximally responsive to what sounds?
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those arising directly lateral to it.
-LSO neurons are less responsive to those arising in front or from the opposite side |
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Where are the auditory radiations found?
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in the sublenticular limb
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Where is the primary auditory cortex? What other broamans/ names?
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Anterior Transverse Gyrus
AI BA 41 |
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Where is the secondary auditory cortex? What other broamans/ names?
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posterior transverse temporal gyrus; planum temporale
(AII) -Brodmann area 42 |
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Where is association area 22?
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Posterior superior temporal gyrus-
Wernicke's area |
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Where is association areas 39 & 40?
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(Inferior parietal lobe) - angular and supramarginal gyrus
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What is association areas 44 & 45?
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(inferior frontal gyrus; pars opercularis, pars triangularis; Broca’s area
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What would damage to BA 22 cause?
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defects in speech comprehension
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What would damage to BA 39 & 40 cause?
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part of wernicke's- would affect aspects of language such as reading & writing
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What determines the response of the LSO neuron?
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-balance of excitation (I/L ear)
and inhibition (C/L ear) |
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-LSO neurons are maximally responsive to what sounds?
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those arising directly lateral to it.
-LSO neurons are less responsive to those arising in front or from the opposite side |
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Where are the auditory radiations found?
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in the sublenticular limb
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Where is the primary auditory cortex? What other broamans/ names?
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Anterior Transverse Gyrus
AI BA 41 |
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Where is the secondary auditory cortex? What other broamans/ names?
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posterior transverse temporal gyrus; planum temporale
(AII) -Brodmann area 42 |
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Where is association area 22?
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Posterior superior temporal gyrus-
Wernicke's area |
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Where is association areas 39 & 40?
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(Inferior parietal lobe) - angular and supramarginal gyrus
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What is association areas 44 & 45?
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(inferior frontal gyrus; pars opercularis, pars triangularis; Broca’s area
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What would damage to BA 22 cause?
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defects in speech comprehension
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What would damage to BA 39 & 40 cause?
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part of wernicke's- would affect aspects of language such as reading & writing
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