auditory system Flashcards
functions of sound
communication
emotion
sound recognition
3D view of world
survival
what features of sound are encoded
frequency Hz (pitch)
intensity dB (volume)
onset
duration
pathway of sound
external auditory canal -> tympanic membrane -> tympanic cavity (ossicles) -> round window -> cochlea
chambers of cochlear spiral
scala vestibuli
scala media
-> organ of corti
scala tympani
organ of corti
contains hair cells
sensory transduction
in scala media
organisation of mammalian cochlea
tonotopic organisation
spiral structure = extends freq range (as many hair cells in space)
- cells at base = high freq
- cells at apex = low freq
place frequency code
position of active IHC along cochlea that encodes the sound freq
how does sound of one frequency activate a specific IHC?
- cochlear tonotopicity is established by basilar membrane travelling wave
- Sound of one frequencycauses maximal movement of the basilar membrane (BM) at one location
what is characteristic frequency
Sound of one frequencycauses maximal movement of the basilar membrane (BM) at one location
low freq sound features
- high energy → travels further along BM
- causes maximal movement toward apex
- CF location closer to apex
- long wavelength
high freq sound features
- low energy → travels less far along BM
- maximal movement toward base
- CF location closer to base
- short wavelength
characteristic frequency is determined by
width and stiffness of basilar membrane
what freq are base hair cells stimulated by
high freq
what freq are apex hair cells stimulated by
low freq
what are the primary sensory receptors of auditary system
inner hair cells
how is sound tranduced to an electrical signal
travels through ear into cochlea and moves basilar membrane in a position dependent on freq (determines what sound)
perilymph in SV and ST move hair bundles on inner hair cells causing shorter stereocilia to move toward longer stereocilia and transducer channels to open. Influx of calcium -> afferent neurone
voltage of resting IHC
-55mV
voltage of excited IHC
-30mV
voltage of inhibited IHC
-65mV
sustained stimulation of inner hair cells
- hair cell moves back and forth at sound frequency
- cycle of membrane potential matching sound frequency
- sensory info relayed to brain via afferent neurone
K movement through IHC during stimulation
enters down electrical gradient and leaves down chemical gradient due to separation of endo and perilymph
role of outer hair cells
amplification of cochlea by moving basilar membrane more
structural differences of outer hair cells
V shaped hair bundle
3 rows
containes prestin in cell membrane allowing stereocilia to lengthen and shorten in response to sound -> moves BM
resting potential of outer cells
-40mV
outer hair cells response to stimulation/inhibition
stim = depolarised = shorten in length (moves BM down)
inhib = hyperpolarised = lengthen
