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What is the Auditory pathway
- Cochlear nerve
- Cochlear nuclei
- Superior Olive complex (via lateral lemniscus)
- Inferior Colliculus
- Medial Geniculate body
- Auditory cortex
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What frequency spectrum do humans hear
20-16,000 Hz (20,000 Hz in children)
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What is the threshold of dB for humans before damage begins
120 dB
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Which portion of the cochlea is damaged first
The base (closet to the oval window) high pitch sounds
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How many inner hair cells do we have at birth
3500
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How many outer hair cells do we have at birth
12-15,000
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The outer hair cells in the cochlear amplify sounds how much
10,000 times
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What is the job of the inner hair cells
They transmit the amplified signal
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Stereocilia in the cochlea are connected how
Tip links
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What causes the K+ and then Ca+ channels to open in the cochlear
When the tip links are pushed toward the longest cilium in the bundle
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When the basilar membrane moves, what else moves
The entire structure is moved
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Outer hair cells have an internal motor molecule called
Prestin, this contracts the cell according to the frequency
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What are the two major groups of drugs that are damaging to hair cells
- Antibiotics (aminoglycoside, kanamycin)
- Chemotherapy (cisplatin)
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What is a unique ability that the hair cells have that make them useful for testing babies ears
- They can produce swinging sounds that can be heard by a microphone
- (Otoacoustic Emission)
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What kind of neurons are the Cochlear nerves
Biopolar neurons
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95% of the spiral ganglion communicates with
The inner hair cells
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What is the ratio of ganglia cells to inner hair cells and outer hair cells
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Where are the ventral and dorsal cochlear nuclei
Medulla-Pons
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What makes the Auditory pathways unique
They can be both ipsilateral and contralateral
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What will result from damage to the auditory pathway above the superior olivary nuclei
There won't be complete deafness due to the bilateral innervation
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Where is the primary auditory complex
Superior temporal gyrus area 41
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How is the primary auditory cortex organized
It has awareness of frequency, loudness, and localization (but not words)
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Where is the secondary auditory cortex and associated areas
Wernickes areas (Br 39, 40)
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Wernickes aphasia
- Patients can speak but it makes no sense (word salad)
- They cannot understand others words, or their own
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What happens to the auditory cortex in deaf people
It becomes more dedicated to visual information mainly sign language and reading lips
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What is the ability to have selective hearing coined
Cocktail party effect (Efferent Pathway)
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What is significant about the ear muscles tensor tympani and stapedius
They have the ability to limit transmission from the middle ear protecting it from damage by harmful noise (Attenuation reflex)
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Hyperacusis
Sensitivity to loud sounds
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Unilateral hearing loss indicates
A disorder in the ipsilateral outer, middle, or inner ear, CN VIII or the dorsal/ventral cochlear nuclei
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If there is a conduction issue with the ear there are problems where
External or middle ear
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If there is a sensorineural problems would be caused by
Disorders of the cochlea or cochlear nerve
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What is the difference between sensorimotor and conductive transmission of sound
- Sensorimotor involves bone conduction and the sensorimotor pathways
- Conductive uses air conduction and the normal hearing pathway
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Rinne test
- Air conduction is compared to bone conduction of each ear by using a tuning fork on the mastoid process and then in front of the ear.
- AC>BC = Normal or sensorineural damage
- BC>AC = Conductive damage
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Webers test
A patient is asked where the tone sounds are louder with a tuning fork when placed in the midline of the forehead
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In the Webers test how are the results read clinically
- With conductive hearing loss, sound is louder in the affected ear
- With the sensorineural hearing loss, sound is louder in the normal (unaffected) ear
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Tinnitus
Noise in the absence of external stimuli
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What are the two major types of hearing aides
- One that amplifies sounds
- Cochlear implants that directly stimulate the nerve
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