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40 Cards in this Set
- Front
- Back
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Frequency/Pitch
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Number of waves per second. Measured in Hertz
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Intensity/Loudness
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Amplitude.
Measured in decibels Increase of 10 is sound that is twice as loud. |
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Human ear sensitivity range
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20-20000 Hz
Can detect a change of one hertz. However, we are most sensitive to 1000-4000 Hz. |
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External ear func.
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Amplifies sound, provides directional information
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Tympanic membrane
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Pars tensa (dense, fibrous, light reflex)
Pars flaccida (fibers present, weakest area of TM) |
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Tympanogram
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Can measure eustachian tube function.
Measures complience of TM. This compliance is greatest when middle ear pressure is equal to ambient and is reduced with eustachian tube dysfunction/fluid. |
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Sound traveling through 2 windows
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In the oval window, out the round.
Oval window is connected to fluid space in cochlea (the scala vestibuli--which contains perilypmh) |
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Perilymph
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Communicates with CSF - scala vestibuli ad scala tympani.
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Endolymph
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Unique to inner ear.
Scala media. High in K to create endocochlear potential. K recycled through gap junctions. Connexin gene defects (affects gap junctions) can result in congenital hearing loss. |
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Inner hair cells
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AFFERENT
Within organ of corti. One row, contact tectorial (via stereocilia). |
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Outer hair cells
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EFFERENT
Three rows, V shaped, connected to tectorial (via stereocilia). |
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When do basilar membrane and tectorial membrane move?
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As the stapes move in and out of the oval window.
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Movement of hair cells
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Excited as stereocilia are displaced to kinocilium, this is turn opens K channels to allow cell to depolarize and release glutamate.
Glutamate causes an increase in the spike rate in an auditory nerve. |
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Low frequencies heard at...
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Apex of basilar membrane.
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High frequencies heard at...
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Base of basilar membrane.
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Auditory afferents
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Spiral ganglion, CN VIII, cochlear nucleus, superior olivary complex, nuclei of the lateral lemniscus, inferior colliculus, medial geniculate body, primary auditory cortex (temporal lobe)
(this is the correct order) Input is bineural. |
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Inferior colliculus
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In midbrain - receives input from superior olive.
Projects to medial geniculate, where complex encoding occurs to integrate many aspects of sound. |
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Primary auditory cortex
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Most responsive to sound in contralateral ear - but input is bineural.
Necessary to produce speech. |
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Auditory brainstem response
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ABR.
Good for indicating tumors of CNVIII It is the electrical signal evoked from the brainstem after presentation of a sound. Can map the sequence of neuronal firing through the pathway of hearing. Primarily used for hearing testing in infants. |
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L Hemisphere
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Better for speech and sophisticated language.
Enhanced temporal resolution |
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R hemisphere
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Enhanced spectral resolution.
Primarily for processing tonal stimuli and music. |
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Efferents of the ear.
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ear can generate sounds, via the OUTER hair cells. (olivocochlear efferent system).
Inner hair cells are for afferents. Hyperpolarization causes elongation of the hair cells, depol causes shortening. |
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otoacuostic emissions
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Measures outer hair cell contraction.
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Facial nerve gives off...
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Nerve to the stapedius to help dampen sound.
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Elevated reflex threshold of sound.
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Indicates cochlear sensitivity loss of VIII nerve disorder.
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Absent reflex to sound
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Abnormal middle ear system
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Severe sensitivity loss to sound due to...
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VIII nerve lesion or ipsilateral VII nerve lesion.
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Audiogram
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Assesses level of hearing and to what frequencies you are best able to hear.
Measures both air and bone conduction. |
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Causes of conductive hearing loss
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infection
tumor trauma cyst congenital. |
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Causes of sensorineural hearing loss
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Age/noise
hereditary congenital. |
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Cerumen impaction
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Tuning fork shows bone conduction greater than air.
Audiogram shows conductive loss. Tympanogram shows occlusion. |
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Otitis media
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Due to middle ear fluid/infection.
Tympanogram show TM to be flat with no movement. Tuning fork - BC > AC Audiogram shows conductive loss. |
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Damage to middle ear bones
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Exam and tympanogram are relatively normal.
Tuning fork shows greater bone conduction than air Audiogram shows conductive loss. |
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Cholesteatoma
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Retraction of eustachian tube resulting in an ingrowth of skin and bone destruction/infection.
(so this follows the findings you would see with damage to middle ear bones) |
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Otosclerosis
(Hereditary ossicular fixation) |
Exam and tympanogram are normal.
Acoustic reflexes are absent Tuning fork shows BC > AC and audiogram shows conductive loss. |
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Noise/age related hearing loss
(hair cell damage) |
Exam and tympanogram are normal.
Tuning fork - AC > BC Audiogram shows high freq sensorineural hearing loss. |
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Mneiere's syndrome (Abnormality of endolymph)
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Exam and tympanogram are normal.
Tuning fork shows AC > BC Audiogram shows low freq FLUCTUATING sensorineural hearing loss. Vertigo is also common. |
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Acoustic neuroma/vestibular scwannoma (Benign tumor)
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Exam and tympanogram is normal.
Tuning fork shows AC > BC. Audiogram shows sensorineural hearing loss. Auditory brainstem response is abnormal. Poor speech understanding. |
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Temporal lobe lesion (stroke or tumor)
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Exam and tympanogram is normal.
Tuning fork shows AC > BC Audiogram is normal Poor speech understanding Auditory brainstem resposne is normal. |
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Superior semicircular canal fistula (inner ear conductive hearing loss)
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Exam is normal.
Tympanogram shows vertigo (?) Tuning fork shows BC > AC Audiogram shows conductive hearing loss. Vertigo. Third window effect. Laxity in fluid spaces. |
