Hearing Flashcards
hair cells
sensing cells in the ear
hair cells contract
rapidly in synchrony with sound
-responding to pitch, tone and loudless
Anatomy of the ear: what separates the outside of the ear (air) with the inner portion of the ear (fluid)
the ear drum
sound waves travel
diff through air and fluid
what allows the transmission of sound waves from the air to the fluid in the inner part of the ear
the OVAL window
where is the oval window found
the ossicles
three bones of the ossicles
malleus, incus and stapes- conduct vibrations to the oval window
the organ of corti
is the hearing sensing organ
organ of corti is made up of
hair cells, which are connected to the tectorial membrane and the basilar membrane
tectorial membrane is closest to the
scala vestibular
basilar membrane is closest to the
scala tympani
the scala vestibular, scala media and scala tympani are all filled
with special, differing fluids –> mechanical sensing
how vibration is conducted around the cochlea
vibration transferred to oval window
- generates fluid wave down the scala vestibule, then through to the scala tympani to the round window
as the sound passes around the cochlea
the vibrations are also conducted to the organ of corti, via a displacement of the membrane
three differing fluids of the ear are located in
the scala vestibular/ tympani (ECF), the scala media (endolymph) and the hair cell (ICF)
fluid in the scala vestibular/ tympani
extracellular fluid
fluid in the scala media
endolymph
- similar to intracellular fluid
- VERY HIGH CONC OF POTASSIUM (150 mmol/L
- potential of +80mV
- low sodium conc
how the different fluid compositions work
electrochemical potential between these fluids
where is there the highest conc of potassium
the endolymph within the scala media
there are fewer
inner hair cells and they ar ea single row
outer hair cells (further into the cochlea)
parallel rows of cilia of hair cells embedded into tectorial membrane
base of hair cells is in contact with the
basilar membrane- which is more flexible- transmits wave
cilia are bathed in
a high conc of potassium
outer hair cells
amplify the vibration
when strain is put on the basilar membrane
strain is put on the cilia, therefore they will bend in response
this strain
will open and close mechanically gates K+ channels
- causing depolarisation and repolarising
potassium is
recycled through the structure
cochlear nerve fibres than transit AP
to the CN VIII part of the CNS- vestibulocochlear nerve
overal process of hearing
1) sound wave
2) vibration of organ of court
3) bending oc cila on hair cells
4) change in K+ (mechanically gated) conductance of hair cell membrane
5) Oscillary receptor potential (cochlear microphonic)
6) intermediate glutamate release
7) excitatory to NMDA/ AMPA
8) intermittent AP in afferent cochlea nerves
9) cranial nerves
10) temporal pathway
pitch is determined by
frequency of the signal
higher frequencies
closer to the oval widnow
lower frequencies
near helicotrema
loudness
identified by the amplitude of deflection at a given part of the cochlea
inner hair cells
Transduce the mechanical signal (vibration) into an electrical one via opening of mechanically gated K+ channels
outer hair cells
At to amplify the vibration by adjusting their length to modify the basilar membrane (positive feedback)
