09 16 2014 Auditory system Flashcards Preview

Neurology 1- M2 > 09 16 2014 Auditory system > Flashcards

Flashcards in 09 16 2014 Auditory system Deck (18)
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Volley theory

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

-basilar membrane


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


Characteristic frequency

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.


Meniere's Disease

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

contralateral innervation
Medial olivocochlear bundle
direct synaptic contacts


Innervation of inner hair cells

mostly ipsilateral innvervation
Lateral olivocochlear bundle
axo-axonic contacts with bipolar cells


Rinne Test

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


Weber test

Tuning fork is placed on the vertex of skull in the midline. Patient is asked to where the tone sounds louder.

-normal: middle
-to one side: air conduction louder on affecter side OR louder on side that can hear (bone conduction defect)