Inner Ear Review 2 Flashcards
Why is IMM important
helps to overcome loss of the sound wave coming in acoustically
these cells are the first row of supporting cells only for the OHC’s, all the way up to the stereocilia
Dieter cells
these support the whole structure of the organ of corti
Hensen’s cells
help create the tunnel in organ of corti
outer and inner pillars
picks up info and carries it away
afferent/sensory
going to the motor unit
efferant/motor
Explain sound process to this point
Sound is funneled by the pinna into the EAC striking the TM (acoustic) - Ossicles vibrate (mechanical) and increase in energy due to IMM - footplate rocks into oval window in the scala vestibuli - Wave gets released through the scala tympani at the round window - wave also stimulates the BM at the best frequency releasing neuro chemicals to be sent to the brain (electro-chemical)
connects the scala media of cochlea to the saccule
ductus reuniens
this attaches to the membraneous portion running through the vestibular aqueduct to the sac to empty into the dura in the brain
endolymphatic duct
The cell bodies for cochlear fibers of CN VIII are
spiral ganglia
The cell bodies for vestibular fibers of CN VIII are
scarpa’s ganglia
the thin passageway that connects the saccule to the cochlear duct is:
ductus reuniens
fluid inside the ductus reuniens?
endolymph
how many vestibular sensory epithelial areas are there in one ear?
5
how many vestibular sensory epithelial areas are there in one head?
10
List the areas where you find the sensory epithelium with vestibular hair cells within the inner ear?
3 ampullae (anterior, posterior, lateral), utricle, saccule
How do the waves travel from the stapes footplate?
- across reissner’s membrane where the fluid pushes down from vestibuli to tympani and then out the round window
- entire length of the BM is displaced (regardless of pressure) but due to stiffness gradient of BM, the frequency of the wave will dictate which organ of corti along the BM will be max displaced
endolymph is high in
potassium
ST, SV and CSF are high in
sodium
Are compositions of perilymph in ST and SV the same?
No, SV has higher potassium and lower sodium
What is endocochlear potential
endolymph has low calcium content and held at a positive voltage (80-85 mV) and only found in the cochlear duct
Where do we find the highest EP?
highest at the basal turn and decreases towards the apex
What is EP dependent on?
metabolism and ion transport
If there is anoxia or occluded blood supply with ion transport inhibitors (diharetics), what happes to EP
rapidly falls and becomes negative
What is the site of EP generation
stria vascularis
What is the most common inherited cause of sensorineural deafness?
defects in genes that code for connexin proteins that form gap junction
ion transporters of stria vascularis are the same as those in what
kidney
concentration in solutions
millimolar
process of the hair cells turning mechanical energy into a potential change
potassium in through stereocilia, calcium in through cell wall channels, carries glutamate+ out to CN8 afferent ganglion
Process of the sensory system receptors
External stimulus — accessory structure — sensory receptor cell — synapse — sensory neuron — synapse
What are the specialized sensory neurons for our hearing system?
OHC IHC
What does it mean to have “graded” sensory receptor cells
Amplitude modulated (increased stimulus intensity = increased voltage change)
Simplified sound transmission process:
- Sound strikes the tympanic membrane
- Bones vibrate
- Oval window moves fluid in the scala vestibule
- The fluid pushes on the respective location of the basilar membrane and activates the movement of the tectorial membrane
- The stereocilia are activated to open ion channels
- Waves are dissipated back into the middle ear space through the round window
what lays on top of the outer hair cells steriocillia?
Tectorial membrane
what supplies blood and oxygen to the cochlea?
stria vascularis
ratio of outer to inner hair cells
3 outer to 1 inner
the cochlea is ______ organized
tonotopically
high frequencies are at the
base
the OHC only enhance sounds from _________ dB
0-40 dB
what do the sereocilia sit on?
cuticular plate
What is depolarization?
make something more positive
inside of hair cells from -45 mV to 0mV
excitatory process
What is hyperpolarization?
make something more negative
overshoots and goes from -45 ot -65 mV
inhibitory in neural transmission
