Auditory System Flashcards
What do we use sound for?
communication, emotion, survival
What does sound cause
one dimensional movement of the two eardrums
Sound frequency units
pitch - Hz
Sound intensity units
loudness - dB
How is sound frequency achieved
cochlear mechanics and physiology of hair cells
How is sound intensity achieved
firing rate of many ANFs
How is the ear adapted for sound duration
specialised sensory cell synapses for sustaining high rates of neurotransmitter release
What features of sound need encoding
frequency, intensity, onset, duration
What innervates the cochlear
auditory nerve
What lies on the basilar membrane
organ of corti
What are the chambers of the cochlea
scala vestibuli, scala media and scala tymphani
characteristics of endolymph
high potassium, low calcium
Perilymph characteristics
normal
Structure of the cochlear
spiral
Cells at the top of the cochlear detect
low frequencies
What is preserved throughout the auditory pathway
tonotopicity
What establishes tonotopicity
basilar membrane travelling wave
What are all hair cells defined by?
stereocilia hair bundle and MET channels
Where are MET channels located
tips of shorter hair cells
How are MET channels opened
force applied to tip links - opens channels
What channels are located on the basolateral membrane of general hair cells
voltage gated Ca2+ and voltage gated K+ channels
What ion causes the inward resting transducer current
potassium
What is surrounded by endolymph?
apical surface of hair cells and stereocilia
True or False - endolymph and perilymph mix
false
Effect of large movement/deflection of hair bundle on cell
channels open, large transducer current depolarises the cell
Excitatory deflection of hair bundle on APs
rapid train of action potentials
MET current during inhibitory deflection
NO MET current
Transducer channels closed causes
hyperpolarisation
Inner hair cells
primary sensory receptors of mammalian cochlear
Difference between IHC and general hair cell
number of different potassium channels on cell membrane
Membrane potential oscillations
MP oscillates between depolarisation and hyperpolarisation at the same frequency as sound
Inner hair cell hair bundle deflect effect
hair cell depolarises and nerve activity increases
When do oscillations saturate
2/3 kHz
How does the cell respond to sound frequencies above 2/3 kHz
sustained graded receptor potential
What is the function of OHCs
cochlear amplifier
What is present on OHCs cell membrane
prestin
Prestin function
allows cells to contract in response to changes in MP
Efferent fibres effect on OHCs
inhibitory - turn OHCs off
What are efferent fibres associated with
post-synaptic cisterns
Resting transducer current is larger in
OHCs
Effect of sound on OHCs
cell shortens and elongates
Depolarisation effect on OHCs
shortens
Function of OHCs up and down movement
positive feedback, increases movement of basilar membrane, to increase IHC stimulation
Which afferent neurons in the cochlear are resilient to nerve damage
type 1 SGNs
What do type 1 SGNs innervate
IHCs
Function of type 1 SGNs
carry all sound information from IHCs to cochlear nucleus
What do type 2 SGNs innvervate
OHCs
Function of Type 2 SGNs
not known, thought to be related to nociception in cochlear
Characteristics of type 2 SGNs
branched, synapse in cochlear nucleus
Sound information transport
carried to brain via type 1 SGNs, type 1 SGNs contact IHCs and type 2 SGNs contact OHCs
