Inner Ear Flashcards
(34 cards)
What is the primary function of the cochlea?
To conver the acoustic signal into electrical energy that can be utilized by CN 8.
What are the last waystations for translating the mechanical energy to hydrodynamic energy to electrical energy?
junction of the stapes and cochlea (oval window)
When does frequency and intensity information get processed?
Within the cochlea via hydrodynamic and electrical events
Where are the auditory and vestibular structures housed?
Temporal bones
What are the four major portions of the temporal bone?
- Tympanic
- Mastoid
- Squamous
- Petrous: where middle and inner ear are
What are the three sections of the scalae in the cochlea?
- scala vestibuli (oval window)
- scala media (cochlear duct)
- scala tympani (roudn window)
What are the two types of fluids found in the scale?
- perilymph (high in sodium, low in potassium; vestibuli and tympani
- endolymph (high in potassium, low sodium; media)
What are the two fluid systems with in the cochlea?
cochlear aqueduct (perilymph)
vestibular aqeduct (endolymph)
Where is the Organ of Corti located?
Basiliar membrane in the scala media
Describe the apex and base of cochlea.
Apex is wide and loose for LF; mass-dominated
Base is thick and stiff for HF; stiff-dominated
What is the true sensory organ of the inner ear?
Organ of Corti
How are signal transmitted in energy in the IE?
hydrodynamic forces are translated into electrochemical energy and sent to auditory nerve fibers.
What are the characteristics of the OHCs?
contains contractile protein for active cochlea mechanism.
3-5 rows
fewer afferent connections; type II fibers unmyelinated
many efferent connections; myelinated
stererocilia (50- 150); embedded in tectorial membrane and moved by movmement of tectorical membrane
electromotility which amplifies
What are the characteristics of the IHCs?
tightly supported by supported cells; stronger HCs
one row
majorit afferent connection; type I fibers (myelinated)
few efferent connection (unmyelinated)
sterocilia (50-75 per IHC); moved by endolymph
mechanotransduction which is connected to nerve fibers, which sends info to brain
“responsible for sending acoustic vibrations into electrical signals that are sent to brain”
Passive vs. active mechanics
passive:
*powered by simple sound progration as sound is passing through
*both stiffiness and mass will affect the acoustic wave in varying degrees
active:
*vibrations powered through additional energy powered by the help of the OHCs
*BM moves up and down using sheer force at the apical end of OHCs b/t tectorial membrane and sterocilia
*cochlear amplifier which helps soft sounds
Mass and stiffness contribute to what?
tonotopical organization
apex (mass)
bass (stiff)
What happens during the condensation/compression phase of the active mechanism? Inhibitory or excitatory?
TM moves inward
pushes stapes into oval window
causes downward motion of BM
moves HCs toward stria vascularis (lateral wall), which shears stereocilia toward the modiolus (medial)….creating hyperpolarization of HCs and release of GABA
INHIBITORY
What happens during the rarefaction phase of the active mechanism? Inhibitory or excitatory?
TM and stapes footplate moves outward
BM moves upward
HCs moves towards the modious and stereocilia…deflects towards stria vascularis cell to releases glutamate (an excitory neurotransmitter) into the intercellular space.
EXCITATORY
What is DERP?
depolarize
excitatory/ inward
rarefaction
positigve auditory effect
What is CHIN?
condensation
hyperpolzation
inhibition/inward
negative auditory effect
The oscillation rate (speed) of the stapes dictates _____
frequency
The amount of displacment of stapes footplate dictates ___
intensity
What are the different functions in charged of fine tuning?
metaboic fxn
neural tuning
nonlinearity
The cochlea amplifier stimulates motor proteins called what? what are their functions?
prestin
to shorten and lengthen, to enhance the flow of the endolymp across the IHC stereocilia
