Auditory Flashcards
what two things is sound characterised by
pitch (tone/frequency) and intensity (amplitude)
where are the hair cells located
inner ear
what does the outer ear do
amplifies sound pressure for frequencies 2-5khZ
localisation of sound
what does the topographical organism in the basilar membrane allow us to distinguish
frequencies/pitches
what causes the basilar membrane to undulate
fluid movements in the cochlea caused by pressure waves generated by incoming sound waves
how does vibrational energy get transduced into electrical signal
the mechanical movement of the hair cells
what’s the difference between inner and outer hair cells
ohc- efferent inputs: receive signals from the CNS
ihc- afferent inputs: send signals back to the CNS
what are stereocilia
actin based protrusions on inner hair cells converting sound to electrical signals
what is the endo-cochlear potential
stereocilia are bathed in endolymph (high k+); the basolateral surface is bathed in perilymph (low k+) - endolymph v +ve compared to inside of cell so the ions will enter the cell
deflection towards the largest stereocilia causes….
more ion channels to open, more k+ enters, more neurotransmitter release, cause action potential - depolarisation
deflection towards the shortest stereocilia causes
hyperpolarisation - k+ channels close, no neurotransmitter release, decreased firing rate
what is labelled line coding
a single neurone responds maximally to a very specific stimulus (eg tonotopic organisation of the basilar membrane)
what is the function of outer hair cells
amplifying and sharpening the sound
based around their electromotility
how does the electromotility of outer hair cells contribute to their function
contract (depolarisation) and expand (hyperpolarisation) in response to electrical currents amplifying motion of the basilar membrane enhancing responsiveness of the inner hair cells
what ganglia is involved in auditory signals
the spiral ganglion
info from each ear reaches what structure first
the superior olive
who suggested the idea of coincidence detectors for the localisation of sound
Lloyd Jeffress (1948)
what is the model for sound localisation proposed by Lloyd Jeffress
added time delay lines so that the sound would arrive from both ears at the coincidence detectors at exactly the same time producing a larger response
where does encoding of sound localisation occur
within the medial superior olive
how was Jeffress model developed to incorporate an anatomical method of producing a time delay
the closer the sound the longer the path to the detector so that they converge on the same neuron in the array between the signals. each neuron corresponds to a specific location in terms of your periphery, converting and electrical signal to a place code
