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59 Cards in this Set
- Front
- Back
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What are the two basic components of the Outer Ear?
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Pinna and External Auditory Meatus.
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Locate the 6 landmarks of the pinna.
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1. Helix
2. Lobule 3. Antihelix 4. Concha cava 5. Tragus 6. Antitragus |
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What is the first function of the pinna?
What is the second function? |
1. Collecting Sound energy
2. Localization of sound |
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Where does the external auditory meatus end?
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Tympanic Membrane
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What makes up the lateral one-third of the EAM? Medial two-thirds?
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Lateral one-third, cartilaginous; medial two-thirds is temporal bone
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What is the function of the pars flaccida of the tympanic membrane?
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It allows the TM to give to prevent rupture from occuring.
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What does the cone of light tell us about the TM?
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That the TM is nice and tight.
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What are the tiny bones that make up the middle ear?
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Ossicles (malleus, incus, stapes)
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Describe the process of the acoustic signal starting from the pinna and ending at the oval window.
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-> Acoustic signal received by pinna
->Funneled into EAM ->Reaches the TM, which will cause it to cave medially ->The air signal turns into vibration ->Malleus is pushed in as well and begins to vibrate ->Vibrations go down ossicular chain and into the oval window |
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What is the particular structure of the malleus that serves as an attachment to the TM?
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Manubrium
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What are the two important muscles attached to the ossicles?
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Stapedius muscle and Tensor Tympani.
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Describe the location and function of the Stapedius muscle.
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Embedded in bone of the posterior wall of middle ear and Comes in from behind the ossicles and connects to the stapes. It pulls the stapes posteriorly and tightens the ossicular chain.
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Describe the location and function of the Tensor Tympani muscle.
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Comes from the anterior wall of the middle ear and inserts in to the upper manubrium of the malleus. Pulls the malleus anteriorly, tightening the ossicular chain. Also reduces the range of movement of TM. Reduces transmission of lower frequency sounds.
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Where does the oval window open into?
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The vestibule of the inner ear.
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Where does the round window open into?
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Scala tympani of the cochlea.
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From where to where does the Eustachian tube extend? What are its two functions?
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The middle ear to the nasopharynx.
1. Allows fluid to drain from and air to circulate in ME. 2. Allows you to equalize pressure in ME with atmospheric pressure. |
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What are the 3 structures you need to be familiar with for the inner ear? What are their functions?
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1. Vestibule - the entry way into the inner ear
2. Vestibular system- (semicircular canals) process balance 3. Cochlea - processes information you hear |
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What is the function of the osseous semicircular canals?What type of fluid are they filled with?
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They are the sense organs for movements of the body in space.
Endolymph. |
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What do the semicircular canals do?
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When you move your head around the endolymph within the rings stimulates the hair cells which are sent to the brain for processing.
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What are the two chambers of the cochlear labyrinth? Name the fluid for each.
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1. Scala vestibuli
2. Scala tympani *Perilymph |
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Describe how sound travels through the cochlear labyrinth.
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The sound comes in the oval window as a fluid wave through the scala vestibuli unti it reaches its peak, the apex, where it forms a hooklike turn, the helicotrem where its meets the scala tympani. The vibrations in fluid will travel all the way to the round window where they eventually fade out.
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What are the three prominent openings of the cochlear labyrinth?
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1. Oval window
2. Round window 3. Cochlear aqueduct |
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What is the function of the round window?
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It serves as the "second tympanic membrane" because its provides a place for the fluid to go and creates some give when the oval window caves medially.
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What is the cochlear aqueduct and what is its purpose?
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Its is the small opening between the scala tympani and subarachnoid space. The subarachnoid space is where the fluid of the inner ear drains so that it can replinish itself.
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What is the scala media? What type of fluid is it filled with?
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The space between the scala vestibuli and scala tympani.
Endolymph |
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What is the Reissner's membrane?
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The top border of the scala media which separates it from the scala vestibuli.
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What is the Basilar membrane?
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The bottom border of the scala media which separates it from the scala tympani.
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What is the Organ of Corti? What is it's function?
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The organ of hearing. Facilitates hair excitation.
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How many rows of inner hair cells are in the organ of corti, how many rows of outer hair cells? Which set are embedded into the tectorial membrane?
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One row of inner hair cells.
Three rows of outer hair cells which are embedded into the tectorial membrane. |
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What are sterocilia?
How are they organized? |
Little hairs that cover each and every hair cell at its upper surface.
They are graduaed in length, shorter closer to the modiolus and longer distal to modiolar side. |
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What it the modiolus?
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The boney center of the cochlea.
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What does movement of the fluid surrounding the haircells do in relation to the stereocilia?
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Movement of one cilia involves disturbance of adjacent cilia on a hair call.
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What is afferent innervation?
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Sensory information is being sent from the body to the brain for processing.
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What is efferent innervation?
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Motor commands being sent from the brain to the body.
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What is the crainial nerve of the auditory system?
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The Vestibulocochlear Nerve (CN VIII)
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How many VIII nerve fibers innervate each inner hair cell?
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10
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How many VIII nerve fibers innervate each outer hair cell?
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One VIII nerve fiber is shared by 10 outer hair cells.
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Why are outer hair cells innervated efferently?
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To limit the unneccesary stimulation of the hair cells.
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What range of frequencies will the ear take in?
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20 Hz to 20,000 Hz.
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What is selective enhancement?
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The outer ear will select energy at resonant frequencies and dampen energy at other frequencies.
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What frequency range will the outer ear amplify? Why is this convenient? How much will the increase?
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1500 and 8000 Hz.
These are speech frequencies. 20 dB. |
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What two structues of the outer ear are the major players for amplification?
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The External auditory meatus and the concha.
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What are the three main functions of the outer ear?
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1. collect sound
2. boos frequencies between 1500 and 8000 Hz. 3. Boost intensity of the frequencies about 20 dB. |
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What are the two primary functions of the middle ear?
(TM, ossicles, oval window) |
1. Change air signal into physical energy (vibration of ossicular chain)
2. Counter the effects of impedance |
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What is impedance relative to the middle ear?
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Resistance to the flow of energy.
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What are the 3 methods to counter impedane in the ME?
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1. Large TM to small oval window (+25dB)
2. Lever difference; malleus to stapes. Inreases force. (+2B) 3. Buckling TM, comparatively less malleus movement (+4 - 6 dB.) |
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What is the total dB increase caused by the middle ear function?
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31 dB to 33 dB.
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What is spectral analysis (IE)?
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The analysis of the specturm, or range of freuquencies coming in.
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According to spectral analysis, what hair cells will higher frequencies stimulate?
Lower frequencies? |
Higher frequencies waves peak and break early->hair cells at base (close to vestibule)
Lower frequencies peak and break later->hair cell at apex (away from vestibule) |
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Describe the process of a sound wave as it travels through the scala vestibuli of the inner ear and ends as a neural signal.
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Sound wave ->scala vestibuli->displaces the Reissner's membrane ->which displaces the basilar membrane ->creates traveling wave along the basilar membrane ->greatest stimulation at point of greatest displacement (of basilar membrane) ->shearing action occurs as the outer hair cell's stereocilia embedded in tectorial membrane are bent -> stimulates a neural response at point of peak displacement ->inner hair cells' stereocilia depend on movement of the endolymph within the scala media via the Bernoulli effect -> neural signal
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The vestibulocochlear nerve is part of the _______ system.
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peripheral
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Discuss the auditory pathway process beginning with the stimulation of the stereocilia created by the point of greates displacement in the wave
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->results in a nerve impulse ->travels the sensory nerve fibers of CN VIII to the brainstem ->where it enters the central nervous system
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What is the first stop once the nerve impulse enters the Central nervous system? What happens?
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Cochlear nucleus of the dorso-lateral brainstem, where sound is first processed.Tonotopic arrangement is observed.
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What is the second stop? Where? Function?
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Superior olivary complex of the dorso-lateral brainstem, at which point the input (phase/timing and intensity) from each ear is finally brought together for processing which helps us localize sounds.
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What is the third stop? Where? Function?
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Inferior Colliculus of the superior brainstem where information will be combined with frequency information.
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From the brainstem, where do the neural signals travel?
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Medial Geniculate Body within the thalamus.
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What is the thalums?
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A subcortical brain structure deep within the brain, and is responsible for processing sensory information, generally speaking.
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What is the function of the medial geniculate body?
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Projects information to the primary auditory cortex in the temporal lobe for final processing.
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What is Heschl's gyrus?
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Part of the temporal lobe, recieves ausitory information and sends speech sounds to Weirnickes area. Distrubutes non/linguistic sound to the temporal lobe.
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