Auditory + Vestibular Flashcards
(35 cards)
Role of External Ear / Ear Cannal
Collecting sound
Sound amplification (select frequencies)
Sound localization (vertical plane)
Role of middle ear
impedance matching
(mediated by ossicles)
Role of inner ear
mechanoelectrical transduction of sound (auditory) and motion (vestibular)
What properties of ear allow impedance matching?
- Area ratio of Tympanic membrane to stapes footplate (20:1)
- Interconnected Ossicles generate leverage
Function of Eustachian Tube
to equalize pressure between Middle Ear and environment
Drain mucus
Otitis Media
disease where bacteria of nasopharynx invade and multiply in middle ear. They gain entry through the Eustachina tube. Generates pressure and pain.
Repeated cases of Otitis Media may result in CONDUCTIVE hearing loss.
Difference between conductive hearing loss and Sensorineural hearing loss
MATTER OF LOCATION!
Conductive hearing loss: middle ear cavity
sensorineural hearing loss: Cochlea & CN VIII
inner ear diagram
Organ of Corti
How are auditory stereociliary bundles moved?
They are deflected by the tectorial membrane
How do fibers of increasing length move together?
linker (tip-link) aids w/ mechano-transduction channel
Two types of fluid in ear
Perilymph: extracellular fluid w/ ionic composition similar to CSF. Perilymphatic Duct drains to the subarachnoid space and is continuous w/ CSF
Endolymph: similar ionic composition to intracellular fluids (high potassium) secreted by stria vascularis. Endolymphatic duct contains specialized epithelia that help maintain pH
name the fluids with which each compartment is filled
another view of fluid filled ear
Explain the steps to mechanoelectrical transduction
- Movement
- Tension placed on Tip-links
- Mechanically-gated potassium channels open
- potassium exits into perilymph
- potassium entry depolarizes the hair cell, opening Ca2+ channels and neurotransmitter is released.
How does the ear do frequency tuning
Resonance and traveling waves. Depending on the freq of the wave, certain parts of the cochlea vibrates. There is compression and rarefaction as the wave travels down the length of the cochlea and returns
Difference between type I and type II Ganglion Neurons (afferent) (that inneravate the cochlea)
Type I
95% of total
Only innervate Inner Hair Cells (1SGN:1ICH)
10-20SGNs/IHC
Perception and Sound Localization
Projects to Cochlear Nuclei
Type II
5% of total
only innervate outer hair cells (8-10 OHCs)
1-2 SGNs/OHC
Auditory feedback, amp?
potential nociceptive function
central circuitry unclear
Efferent Cochlear innervation
Lateral Olivocochlear Neurons:
cell bodies in lateral superior olive
primarily ipsilateral
Synapse onto Type I SGN dendrites
modulate firing rates
Medial Olivocochlear Neurons:
cell bodies in medial superior olive
ipsilateral and contralateral origin
synapse onto outer hair cells
regulate cochlear amplification
Tonotopic orgranization in dorsal cochlear nucleus @ level of medulla/pons
Central Auditory Pathways
Where do tonotopic freq maps occur in auditory pathway?
they’re maintained throughout!
