Passive (Macro) Mechanics / Cochlear Physiology

Question 1

T/F The auditory system is one of the most sensitive systems

Answer 1

True

Question 2

How does the mechanical nature of the cochlear allow for discrimination of different sounds by the brain?

Answer 2

mechanical system is very sensitive; TM deflections are as small as 1/10 diameter of H atom causing hearing; BM movements may be 100 times smaller than this
- movement that small (BM –> action potential)

Question 3

organ of corti review

Answer 3

Question 4

basilar membrane changes in _________ through the cochlear spiral

Answer 4

width

Question 5

narrow @ __________ end

Answer 5

basal end

Question 6

wider @ ___________ end

Answer 6

apical; allows for more vibration

Question 7

attachment point of the tectorial membrane is more __________ than the attachment of the basilar mebrane

Answer 7

medial

Question 8

why does the attachment point of the tectorial membrane being more medial than attachment of the BM aid stereocilia deflection?

Answer 8

more effective shearing force across stereocilia

Question 9

a wider BM will be less _______ than a narrow BM

Answer 9

stiff

Question 10

the difference in _____________ creates a more effective shearing force across stereocilia

Answer 10

points of rotation

Question 11

fluid motions of the scalae (vestibuli and tympani)

Answer 11

macromechanics

Question 12

macromechanics assumes

Answer 12

that the cochlear duct or scala media is a flat cochlear partition and is a dynamic structure exhibiting characteristics of mass, stiffness, and damping

Question 13

mass

Answer 13

weight, wider more cells

Question 14

stiffness

Answer 14

flexibility, wider more flexible

Question 15

damping

Answer 15

loss of vibrational energy due to viscosity of fluids and friction; doesnt play a large role in macromechanics

Question 16

diagram of the cochlear partition

Answer 16

Question 17

there is more ___________ at one location [either basal or apical end]

Answer 17

vibration

Question 18

T/F We cannot use a physical model to show that stiffness and mass can affect resonant frequency

Answer 18

False; we can use a physical model to show that stiffness and mass can affect the resonant frequency

Question 19

of frequency-specific stimuli and measure the resultant amplitude of the vibrations show…

Answer 19

a) frequnecy that peaks in peak amplitude = system’s resonant frequency (RF)
b) increasing stiffness = reduces amplitude of vibrations below resonant frquency and shifts the resonant frequency higher

Question 20

physical model showing stiffness and mass can affect RF

Answer 20

Question 21

Helmholtz described the cochlea as a ______________, each tuned to diff frequency and occupying diff location on the BM

Answer 21

bank of highly tuned resonators

Question 22

what did Helmholtz fail to explain

Answer 22

the coupling mechanism between middle and inner ears - cochlear fluids

Question 23

Von Bekesy was the first to demonstrate the _______________ behavior of the BM

Answer 23

traveling wave

Question 24

Von Bekesy used human cadavers and assumed the BM functioned similar to ______________ membrane

Answer 24

Reissner’s

Question 25

diagram of the traveling wave

Answer 25

Question 26

Von Bekesy also saw the first observation of _________________

Answer 26

tonotopic organization

Question 27

Von Bekesy observed that the cochlear is like a _____________ system in which a “traveling wave” is transmitted along the length of the cochlear

Answer 27

linear dispersity

Question 28

Von Bekesy also observed that a given freq stimulus reaches a peak in vibration amplitude at a ______ and characteristic spot along length of the cochlea

Answer 28

constant

Question 29

for any given freq stimulus, the vibration grows _______ as it moves along the length of the cochlea then more abruptly ___________ after achieving its max vibration

Answer 29

gradually; diminishes

Question 30

as the frequency of the stimulus is _________, the position of the vibration max moves towards the base of the cochlea

Answer 30

increased

Question 31

Von Bekesy’s Assumptions (3)

Answer 31

1) Reissner’s membrane acts similarly to BM
- fair assumption
2) Dead cochlea functioned similarly to undisturbed live cochlea
- not a fair assumption
3) To see vibration waves, Von Bekesy had to use stimulus intensities that were on the order of 130 dB SPL (above pain threshold)
- not a fair assumption

Question 32

Von Bekesy’s shortcoming

Answer 32

did not account for the sharp tuning of the individual auditory fibers

Question 33

Sellick used other techniques such as

Answer 33

Live animals

Question 34

Sellick clarified important points such as (3)

Answer 34

1) BM was responsive to low level stimulus
2) BM was very sharply tuned at this intensity; changing the stimulus freq only slightly caused a LARGE change in vibration amplitude
3) BM response became more broadly tuned as stimulus intensity increased

Question 35

Sellick’s model/diagram

Answer 35

Question 36

the vibration energy of the stapes is tightly coupled to ________

Answer 36

basilar membrane (BM)

Question 37

Helicotrema acts mechanically as if it were ___________ except at very low frequencies (<100 Hz)

Answer 37

closed

Question 38

What does the helicotrema help do?

Answer 38

filter out very low freq sounds such as body sounds of breathing and heart beat

Question 39

the __________ ear is most efficient, but vibration of the skull (tuning fork) works well also

Answer 39

middle

Question 40

the primary determinant of frequency-to-place transformation is the

Answer 40

gradient of stiffness along the BM

Question 41

the BM represents a _____________ system

Answer 41

non linear

Question 42

what does a non-linear system represent

Answer 42

increases in sound intensity does not result in corresponding increases in vibration amplitude of the BM

Question 43

____________ and ____________ are the results of active physiological process and for this reason, are vulnerable to the disease of that physiology

Answer 43

tuning and non-linearity

Question 44

Von Bekesy’s studies could not explain the _________________

Answer 44

high frequency resolving power that the live cochlear must exhibit