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Neuro II p33-50

Thomadaki Fall 2010

What is sound characterized by? Frequency (pitch) & intensity (volume)
Frequency determines ______ and is measured in ____ pitch, cycles/sec or Hz
Range of frequencies audible to humans 20-20,000Hz or 20Hz to 20kHz
Frequency of ULTRASOUND? Heard by who? >20kHz, animals
Frequency of INFRASOUND? heard by who? <20Hz. Elephants and whales
What type of frequencies are implicated in car sickness? Low frequency sounds
3 functional divisions of the ear? External, middle, inner era
External ear is composed of what two structures? PINNA (auricle/tragus) - cartilaginous sound capturing convoluted funnel. EXTERNAL ACOUSTIC MEATUS (auditory canal). 2.5 cm tunnel that ends at ear drum
What is the middle ear filled with? Air
Middle ear is composed of what 3 structures? TYMPANIC MEMBRANE (9mm diam conical membrane) OSSICLES (malleus, incus, stapes) TENSOR TYMPANI & STAPEDIUS MUSCLES
What is the inner ear filled with? fluid
What 2 structures are found in the inner ear? COCHLEA (auditory system) - tube that is spiraling 2 1/2x around conical bony modiolus) VESTIBULE
What is the function of the middle ear? Augment sound
does the convex/concave portion of tympanic membrane extend into the cavity of the middle ear? convex
What are the ossicles held together by? synovial membrane
What ossicle transfers tympanic membrane displacement to inner ear? Stapes
Middle ear cavity connects to the nasopharynx via the ____, usually closed by a ______ and the _________ via the _____ Eustachian tube (auditory tube), valve, mastoid air space (antrum), aditus
Mastoid air space is AKA? Antrum
Tensor tympani attaches to what ossicle? Malleus
Stapedius attaches to what ossicle? Stapes
Function of the tensor tympani and stapedius? Make ossicles more rigid in order to dampen v. loud sound
TT and stapedius decrease sound by what dB? 10dB
What is the attenuation reflex? Contracts, tensing up malleus and stapes, dampening loud sound. (doesn't protect from sudden loud sound).
What is the delay of the attenuation reflex? 50-150msecs
The middle ear amends the sound so what percentage of waves reach the inner ear? Otherwise, what percent of waves would reach the inner ear? 67%, 2%
The middle ear amplified pressure by ____x? What are the 2 ways it does this? 22x; (1) surface area of oval window is 17x smaller than that of tympanic mem & (2) ossicles act as levers and increase force output on the oval window (the mvt on footplate of stapes is 1.3x the mvt of the arm of the malleus)
What are the two holes in the cochlea called? oval and round window
Fluid movement is created when what happens? oval window is displaced by stapes.
Most of the movements of fluid is absorbed by the fluid of the cochlea but any "unabsorbed" energy does what? distorts the round window
What are the 3 fluid filled chambers of the cochlea? Scala vestibuli, Scala media, Scala tympani
What membrane is located between scala vestibuli and scala media? Reissner's membrane
What membrane is located between scala media and scala tympani? Basilar membrane.
What chambers contain perilymph? Scalas vestibuli & tympani
What two chambers connect? where? Scalas vestibuli & tympani; Helicotrema
Ion concentration of perilymph? Low K, high Na
What chamber contains endolymph? Scala media (cochlear duct)
Ion concentration of endolymph? High k, low Na
What structure is responsible for secreting K while absorbing Na against their concentration gradients? Stria vascularis
Where is the organ of corti located? On basilar membrane
Shape of basilar membrane Narrow/stiff toward base; wide and floppy at apex
Base of basilar membrane codes for what type of frequency? High frequency
Apex of basilar membrane codes for what type of frequency? Low frequency
Arrangement of basilar membrane is called what? Tonotopic map
What is the sensory receptor organ of hearing? Organ of corti
What structures compose the organ of corti? Inner and outer hair cells, rods of corti (pillar cells) & surrounding cells.
Organ of Corti is covered by what? Tectorial membrane
The organ of corti is located where? In scala medial which contains endolymph
Each hair cell has ___ (#?) _____ whose bending causes a _____ 100 stereocilia; receptor potential
There are ______ inner hair cells arranged ______, located between the ____ & _____. 3500; row; pillar cells & bony modiolus.
The stereocilia of the organ of corti extend where? Into endolymph inferior to tectorial membrane
Hair cells synapse with? Dendrites of bipolar spiral ganglion cells
Bipolar spiral ganglion cells are located where? And what do their axons form? Modiolus; cochlear n.
What is the function of hair cells? Convert mechanical energy that reaches the inner ear to a receptor potential
Upward movement of the basilar membrane has what effect? Causes sterecilia to bend so that K channels on their tips open & depolarize the hair cells. --> causes Ca channels to open --> release of NTs (maybe glutamate) --> synpase between hair cells & dendrites of spiral ganglion
Downward movement of basilar membrane has what effect? Causes hyperpolarization
Most of the spiral ganglion cells receive synapses from what type of hair cells? Inner hair cells
Outer hair cells are implicated with what? Sound amplification (by augmenting the movement of inner hair cells) in inner ear.
Ototoxic cells selectively destroy what? Outer hair cells
What forms the cochlear n? axons of spiral ganglion cells
Cochlear n travels where? and synapses with what? Medulla; cochlear nuclei
What are the types of cochlear nuclei? and how many of each? 2 ventral; 1 dorsal
What type of cells do ventral cochlear nuclei have? and what do they do? Stellate cells; encode a variety of frequencies and bushy cells which fire at onset of sound and aid in localization of sound along horizontal axis
What type of cell does dorsal cochlear nucleus have? fusiform cells; get excited/inhibited by a wide variety of frequencies and aid in sound localization along the vertical axis and tuberculoventral cells that respond with a delay and inhibit echo interference.
What is the function of tuberculoventral cells? Delay and inhibit echo interference
Sound localization on vertical axis is controlled by what nucleus? Ventral cochlear
Sound localization on horizontal axis is controlled by what nucleus? Dorsal cochlear
Any injury above cochlear nucleus in auditory pathway leads to hearing loss on what side? Hearing loss pronounced contralaterally
Cochlear nuclei synapse bilaterally with? superior olivary nuclei
medial superior olivary nucleus is involved in localization of sound on ________ by _________ horizontal axis; processing info about auditory time delay between 2 ears.
Interaural time delay is most striking in what frequencies? low
Lateral superior olivary nucleus is involved in localization of sound by ____ processing intensity difference between the 2 ears
Intensity interaural differences are most striking at what frequencies? High
Fibers of superior olivary nucleus form the _______ lateral lemniscus
Some fibers of superior olivary nucleus synapse with nuc of _____ but most synapse with _____ lateral lemniscus; inferior colliculus
Inferior colliculus has 4 layered nucleus which gathers ____ &____ info. And a multi layered nucleus that has a ________ auditory and somatosensory; tonotopic map
What shifts head toward stimulus tectospinal tract
______ receives info from inferior colliculus via the ______. Holding a _______. Fibers then form the ______ and end in _______ medial geniculate nuc; inferior brachium; complete somatopic & tonotopic map; auditory radiation; primary auditory cortex
Where is the primary auditory cortex? it is _____ organized Transverse temporal gyri of heschl (41, 42 of brodmann). tonotopically
Where is the second point of determining localization of sound source? Transverse Temporal Gyri of Heschl
Conductive hearing loss results from insult to ______. Examples? middle ear. Otitis media, otosclerosis
Sensorineural hearing loss results from injury to ______ there fore loss of ________ inner ear; cochlear hair cells
if person talks very quietly what type of hearing loss might they have? conductive
Weber's test - put tuning fork where? if sound lateralizes ipsilaterally then it's ______ deafness and contralaterally it's ________ deafness vertex/nasion; conductive; sensorineural
Rinne's test - put tuning fork where? mastoid process, when can't hear sound anymore place it near ear.
What type of hearing loss is tested in Rinne's test? Conductive
Inner ear is composed of what 3 structures Cochlea, Vestibule (utricle & saccule) and semicircular canals
The bony labyrinth contains ______, high in what ion? it is continuous with _____? perilymph, Na, CSF
The membranous labyrinth contains ______, high in what ion? Endolymph, K
Vestibular system helps with what 3 things? Maintenance of posture, muscle tone, eye position with respect to head motion
The labyrinth is subdivided into ______ & _______ static & kinetic labyrinth
Static labyrinth is composed of ______ & ______ which has what function? sacuule & utricle; detects static orientation of head with respect to gravity.
What are the specialized hair cells in static labyrinth called? And they are embedded in ______ which contains _______ macula utricle and macula sacculi; otolithic membrane; CaCO3 crystals
Kinetic labyrinth is composed of _______ which have what function? semicircular canals; detect angular acceleration and deceleration.
Semicircular canals are _____ oriented so they can _____ orthogonally; detect all possible directions of motion.
Where are the specialized hair cells in the kinetic labyrinth located? What are they called? and they are embedded in a _______ called _____ Ampullae; crista ampullaris; gelatinous mass; cupula
Transduction of vestibular system - ____ ion influx causes hair cells to _____. When microvilli bend toward kinocilium the cells will ______; when microvilli move away, the cell will ______ K, depolarize, hyperpolarize
Where does the vesitibular nerve enter the brain stem? cerebellopontine angle lateral to facial n.
Where are vestibular nuclei located? lateral aspect of floor of medullary and pontine part of 4th ventricle - underlying vestibular area
Axons from vestibular nuclei project to what 3 areas? Flocculonodular lobe & fastigial nucleus of cerebellum; spinal cord (vestivulospinal tract); Brainstem nuclei of III, IV and VI bilaterally via MLF
Fibers from vestibular nuclei ascend to the ________ nuc --> _______ of cortex posterior thalamic nuc; parietal association area
Internuclear ophthalmoplegia is caused by a lesion to what structure? What are the symptoms? What diseases do you see this? MLF; Failure of CN III, IV, VI to carry out synchronous horizontal gaze; MS, or vascular d/e
Exams for Vestibular system? BARANY CHAIR - spin around in chair, when stops should have nystagmus CALORIC TESTING: Cold Opposite Warm Same
Central lesion to vestibular system leads to what sx? Nystagmus in various directions in absence of vertigo
Peripheral lesion to vestibular system leads to what sx? Horizontal nystagmus only in presence of vertigo
Meniere's Disease. Onset? idiopathic; dysequilibrium, nystagmus and vertigo coupled with progressive hearing loss and tinnitus. onset age 20-30
Acoustic neuroma - type of tumor? location? May affect what nerves? schwann cell tumor, usually around IAM or cerebellopontine angle; facial & trigeminal
Created by: mrw2013
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