Flashcards in 09 16 2014 Auditory system Deck (18):
group of neurons of auditory system respond to sound by firing action potentials slightly out of phase so that when combined = greater frequency of sound can be encoded and sent to the brain to be analyzed
Phase locking theory
matching amplitude times to a certain phase of another waveform
-firing an action potential at a certain phase of a stimulus sound being delivered
ringing of ears -- can be pops, clicks, or rush
-common cause is inner ear damage
-symptom of menerie's disease
-can also be caused by ototoxins
agents that can damage both auditory and vestibular functions
-aminoglycoside antibiotics (streptomycin, gentamycin) and salcylates.
footplate of the stapes gets locked in place as a result of bone growth around the annular ligament-- goes around stapes.
Annular ligament connects the stapes to the base of the oval window
- bone formation here prevents vibrations
How is pitch perceived?
Place coding in different regions of the cochlear -- selectively responsive to different frequencies of sound
what happens to your ability to perceive pitch when there are very loud sounds around u?
- there is an overlap of frequencies = poor pitch discrimination
each auditory afferent displaces a CF --> the frequency at which the fiber has the lowest threshold to fire -- aka when it will fire vs another fiber
Innervation of cochlea?
Cochlea is composed of inner (1 row) and outer (3 rows) hair cells
90% bipolar cells of the spiral ganglion innervate the hair cells.
10% of spiral ganglion cells innervate the outer cells. Outer cells are also innervated (directly) by efferent fibers!
time differences are monitored by what nucleus?
Medial Superior Olivary nucleus
-sound coming from right arrives at the right ear before the left ear.
-Axons vary in length to try to compensate for sound differences.
intensity differences are monitored by what nucleus?
Lateral Superior Olivary Nucleus
-sound coming from right will be more intense on right
how does one localize where sound comes from?
MSO and the detection of a binaural time difference. Sound hits one ear before the other.
cc: vertigo, progressive hearing loss and tinnitus and feeling of a full ear
-overproduction of endolymp
function of inner hair cells?
Function of outer hair cells?
--detection of sound
-participate in amplifying and dampening of sound stimulus (via motor force)
- motor: contract and elongate in synchrony with sound-evoked receptor potentials (motor protein --> prestin)
Innervation of outer hair cells
Medial olivocochlear bundle
direct synaptic contacts
Innervation of inner hair cells
mostly ipsilateral innvervation
Lateral olivocochlear bundle
axo-axonic contacts with bipolar cells
air conduction is compared to bone conduction
-hit runner, hold near ear (ask them until they stop hearing the sound) then put it on mastoid process and then asking them to tell you when vibration stopped
-conductive hearing loss: bone conduction is greater than air conduction