Hearing Flashcards
what 3 things are being detected by ears?
- wavelength: pitch
- amplitude: loudness
- waveform - tone/timbre
Function of ossicles?
matches air vibrations to fluid in inner ear
tympanic membrane amplifies how much compared to inner ear??
200 fold
3 chambers of cochlea?
- scala vestiboli
- scala media
- scala tympani
Basilar membrane is wider where? what does it detect?
wider at the base (detect high freq)
apex of basilar membrane detects?
apex detect low freq
how is basilar membrane organized?
tono-topically
What is the organ of Corti?
what transduces sound waves to neural impulses
auditory hair cell found between?
basilar membrane and tectoral membrane
each hair cell have how many stereo cilia?
100
how do you trigger auditory transduction?
basilar membrane vibrates> create shear forces on tectorial membrane> depolarize hair cells
Hair cells use what ions to depolarize?
Potassium (K+)
deflection of hair bundle toward kinocilum? away?
towards: depolarization (Ca2+ influx>glutamate)
away: hyperpolarization
hair cell potassium channels are usually closed?
nope. partially open
Are the hair cells depol and hyperpol amounts equal if the movement is equal?
Nope. larger depol
Normal neurons has influx of what ion?
Na+
what makes the potential difference in the cochlea re: ions?
Endolymph at +80mV (High K+)
Perilymph is at 0mV (Low K+)
cell connections in inner ear are called?
vasa vascularis
what’s the difference between inner and outer hair cells?
inner: 95% to brainstem nuclei
outer:
1. enhances tectorial membrane movement
2. efferent inputs from superior olivary complex
how does outer hair cell affect inner hair cells?
low intensity stim>outer change length>increase basilar membrane movement>amplify to inner hair cells
depol and hyperpol of outer hair cells causes what?
depol: contraction
hyperpol: elongation
outer hair cells can be affected by what drugs?
aminoglycosides (gentamycin)
aspirin
ototoxicity
without outer hair cells, how much less does the inner hair cells detect?
100 fold less
Auditory pathway starting at hair cells:
Hair cells>CNVIII>spiral ganglion>cochlear nucleus>decussation>superior olive>lateral lemniscus>inferior colliculus (midbrain)>medial geniculate nucleus of thalamus>auditory cortex
what does the anteroventral cochlear n. and superior olivary complex do?
mediate sound localization (horizontal plane)
superior olivary complex consists of 3 things:
- lateral superior olives
- medial superior olives
- trapezoid body
2 ways to localize sound: know as what theory?
- time difference
- intensity difference
Duplex theory
Time difference for sound localization works well particularily with what?
low frequency sounds
what detects the Time difference for sound localization?
medial superior olive
intensity difference for sound localization for what kind of sound?
high frequency
intensity difference for sound localization, how does the MNTB come into play?
MNTB: medial nucleus of trapezoid body inhibits contralateral LSO (lateral superior olive) excitation
What is in brodmann’s area 41?
Herschls Gyrus (tonotopic)
Higher order of auditory processing: which hemisphere for:
- speech
- music
- environmental?
- left
- right
- both
3 causes of hearing loss within 3hr to 3 days include?
- peripheral: guillan-barre, cancer
- central: MS
- cochlear:infection, trauma, ototoxicity, vascular
