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):
1

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

2

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

3

Tinnitus

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

4

ototoxins

agents that can damage both auditory and vestibular functions

-aminoglycoside antibiotics (streptomycin, gentamycin) and salcylates.

5

otosclerosis

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

6

How is pitch perceived?

Place coding in different regions of the cochlear -- selectively responsive to different frequencies of sound

-basilar membrane

7

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

8

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

9

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!

10

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.

11

intensity differences are monitored by what nucleus?

Lateral Superior Olivary Nucleus

-sound coming from right will be more intense on right

12

how does one localize where sound comes from?

MSO and the detection of a binaural time difference. Sound hits one ear before the other.

13

Meniere's Disease

cc: vertigo, progressive hearing loss and tinnitus and feeling of a full ear

-overproduction of endolymp

14

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)

15

Innervation of outer hair cells

contralateral innervation
Medial olivocochlear bundle
direct synaptic contacts

16

Innervation of inner hair cells

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

17

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

18

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)