auditory physiology

Question 1

pinna

Answer 1

funnel for info directed toward the head from the front or side
-resonator for 2000-5000 Hz (important range for speech recognition)

Question 2

outer ear

Answer 2

capability of selective enhancement of certain freq, due to resonator qualities

Question 3

real ear measurements

Answer 3

accomplished by placing a probe mic or small tube into the outer ear canal and measuring sound pressure
-to figure out what the client is actually hearing (we don’t want to over amplify them)

Question 4

resonance of the external auditory meatus

Answer 4

results in a net gain of approx 10-15 dB around 2700 Hz

Question 5

resonant quality of the concha

Answer 5

around 5000 Hz

Question 6

middle ear

Answer 6

designed to increase pressure arriving at the cochlea and overcome the resistance of flow of energy (impedance)
-main job= impedance matching

Question 7

mechanism for impedance matching

Answer 7

the TM is about 17 times larger than the oval window
-gain is equivalent to an increase of about 25 dB
second, the length of the manubruim is approx 9 mm, while the long process of the incus is 7 mm
-gain of nearly 2 dB
-gain of a total of 33 dB for impedance matching

Question 8

sound transmission

Answer 8

through the middle ear to the inner ear via 3 methods

Question 9

3 methods of sound transmission

Answer 9

• bone conduction
• the air in the middle ear cavity
• through the ossicular chain

Question 10

bone conduction

Answer 10

occurs when acoustic pressure changes cause the temporal bone to vibrate, stimulating the inner ear fluids

Question 11

bone conduction testing

Answer 11

a vibrator is placed directly on the skull, stimulating the inner ear directly and bypassing the middle ear
-differentiates middle ear disorders from sensorineural HL

Question 12

ossicular chain

Answer 12

most effective method for sound transmission in the middle ear
-as the TM vibrates, it sets the OC into motion, thus vibrating the fluids of the inner ear at the oval window

Question 13

changes in air pressure in the middle ear

Answer 13

reduces the efficiency of vibration

-if sound trasmission is not efficient it can cause a HL

Question 14

inner ear

Answer 14

responsible for performing spectral and temporal acoustic analyses of the incoming acoustical signal

Question 15

first level of auditory processing of an acoustic signal

Answer 15

the cochlea sorts out freq components of an incoming signal, determines the amp, and identities basic temporal aspects of that signal

Question 16

subsequent processing

Answer 16

occurs as the signal works its way along the auditory neural pathways to the brain to be perceived

Question 17

what does the footplate of the stapes compress?

Answer 17

the perilymph and distends the BM

Question 18

number of oscillations of the TM

Answer 18

ossicle-footplate combination results in that periodic vibration to the BM, where a wave action initiates called the traveling wave

Question 19

basilar membrane

Answer 19

well designed to support wave action that directly corresponds to the freq of vibration of the input sound

Question 20

what do low freq sound result in?

Answer 20

long traveling wave that reaches the apex covering greater distance along the BM

Question 21

what does the traveling wave do?

Answer 21

separates out the freq components of complex sounds

-high freq sounds are process in the base and low freq sounds are processed toward the apex

Question 22

point of maximum amplitude

Answer 22

is the primary point of neural excitation of the hair cells within the organ of corti
-after it reaches the max, it quickly dampens

Question 23

place of maximum disturbance determines what?

Answer 23

the freq info that is transmitted to the brain

Question 24

as mass of the BM increases..

Answer 24

the resonant freq decrases

-BM becomes more massive and wider from base to apex

Question 25

what combines to make the BM a great freq analyzer

Answer 25

graded stiffness, graded mass, and graded width

Question 26

what type of fluid do the IHCs depend on?

Answer 26

endolymph

Question 27

disturbance at the point of max excitation causes..

Answer 27

a turbulence, which produced swirls of fluid molecules

Question 28

hinge-like arrangment

Answer 28

between the BM and the spiral limbus | -places the OHCs in a position to be activated by the lower level stimulus than the IHCs

Question 29

potential of the scala media

Answer 29

has a constant positive potential (endocochlear potential) relative to the tympani and vestibuli

Question 30

what does damage to the stria vascular result in?

Answer 30

loss or decrease of EP (endocochlear potential) | -strong positive potential comes from the active ion pumping by the stria vascularis

Question 31

what does transduction of neural info take place?

Answer 31

near the top of the haircuts in the region of the stereo cilia

Question 32

what happens during the shearing of the stereo cilia?

Answer 32

tip lengths stretch and a trapdoor opens and closes allowing ions to flow in and out of the hair cell -starts the neural transduction process

Question 33

what is the role of the sterocilia on the OHCs

Answer 33

sensing vibration within the cochlea | -make the cochlea very sensitive to small vibrations

Question 34

OHCs feedback energy

Answer 34

due to its motility and cochlear potentials | -OHCs amplify small vibrations which help stimulate the IHCs

Question 35

what is initiated by the IHCs?

Answer 35

neural events | -sends the signal up the auditory nerve bundle to the brainstem

Question 36

biological transducers for sound

Answer 36

IHCs | -where most fibers for the auditory nerve connect

Question 37

auditory nerve preserves..

Answer 37

the freq, intensity, and timing info from the cochlea and brings this info to the brainstem

Question 38

discharge patterns of the auditory nerve fibers

Answer 38

reflect the freq, intensity, and timing encoding performed by the mechanics of the inner ear -these nerve fibers leave the modiolus of the cochlea in an order manner

Question 39

what do the nerve fibers from the base of the cochlea make up?

Answer 39

outside of the nerve bundle | -carry high freq info

Question 40

what forms the entire VIII nerve tract?

Answer 40

auditory nerve fibers from the cochlea join the nerves from the vestibular system

Question 41

types of afferent fibers

Answer 41

radial fibers and outer spiral fibers

Question 42

radial fibers

Answer 42

type one - comprise 95% of the total number of afferent fibers - innervates IHCs exclusively with 10 radial fibers for every 1-2 IHCs

Question 43

outer spiral fibers

Answer 43

type 2 - constitutes about 5% of the afferent fibers - there is one to many connections - one outer spiral innervation to about 10 OHCs

Question 44

characteristic freq

Answer 44

is the freq where the neurons fire most | the CF is different for each freq

Question 45

what do the fibers on the outside of the auditory bundle innervate?

Answer 45

basal haircells - have high freq CFs

Question 46

what do the fibers toward the middle of the nerve bundle innervate?

Answer 46

with haircells at the apex of the cochlea | -have low freq CFs

Question 47

olivocochlear bundle

Answer 47

done with efferent innervation of the haircells | -series of nerves that come from the olivary complex in the auditory brainstem to the haircuts of the organ of corti