Auditory system Flashcards
What features of sound does the auditory system need to encode?
Frequency
Intensity
Onset
Duration
How many chambers does the cochlea have?
3
What are these chambers?
Scala tympani
Scala media
Scala vestibuli
What is the Organ of Corti?
It is at the bottom of the scala media and contains the sensory hair cells and receives innervation from the auditory nerve
Where is perilymph found?
Scala vestibuli and tympani
What is its relative K+ concentration and Ca conc? (perilymph)
Low K+ and normal Ca
What contains endolymph?
Scala media
What are its concentrations of K+ and Ca? (endolymph)
High K+ and Low Ca
What produces endolymph?
Stria vascularis – pumps K+
What is the membrane potential in the scala media and in the Vm for the hair cells in the organ of corti?
Scala media = +80mV
Hair cell Vm = -60mV
What is the name for this difference in potential?
Endocochlea potential
Which hair cell is the main sensory cell?
Inner hair cell
What is the function of the outer hair cells?
Amplify signals
What do the outer hair cells make contact with?
Tectorial membrane
How many bundles of outer hair cells are there?
3
Where are the low frequency inner hair cells?
At the top
What does each inner hair cell code for?
Particular frequency
What causes the hair cells to move?
Movement of the basilar membrane due to the travelling wave in the scala tympani
- Low frequency travels further along basilar membrane
What does MET stand for? (MET channels)
Mechanoelectrical transducer channels
- Allow current in
Where are they found?
MET channels
On the end of the stereocilia hair bundles
What do tip links do?
Connect and pull on hair bundles
What happens when there is an excitatory deflection?
Maximal tip link extension that fully depolarises the hair cell
What happens when there is an inhibitory deflection?
No tip link extension and hair cell is hyperpolarised
What is the role of the OHC?
Amplify sound
What fibres contact the OHC?
Efferent fibres
What allows the OHC to contract?
Prestin in the cell membrane
What happens when there is depolarisation to the OHC?
Contraction
What does contraction in OHC do?
Increase movement of basilar membrane and IHC stimulation
What tunes the IHC?
OHC to ensure IHC responds to a narrow frequency band
What do type 1 afferents contact?
IHCs
In which way does the auditory system encode the property of sound which is measured on a logarithmic scale?
The rate of firing of action potentials
What is the auditory pathway?
superior olivary complex → superior colliculus → medial geniculate nucleus
Why are low frequency sounds generally localised by interaural timing differences?
high frequency sounds are more susceptible to attenuation by the head
What do the OHC receive efferent input from?
Superior olivary complex
