Physiology of Middle Ear

Question 1

Power Transfer

Answer 1

I2/I1=4Z1/Z2/(Z1+Z2)2

Question 2

Ear Canal Reflectance

Answer 2

Acoustic impedance looking into the ear canal

Question 3

Z0 = ρc/A

Answer 3

p= density of air, c= speed of sound, A= cross sectional area of ear canal

Question 4

Impedance Mismatch

Answer 4

Loss of vibration from air to fluid of inner ear

Question 5

I2/I1 = 4Z1Z2/(Z1+Z2)2

Answer 5

Energy immitted

Question 6

Loss of pressure from ME to Inner ear

Answer 6

37 dB

Question 7

TM area

Answer 7

80 mm

Question 8

Footplate of Stapes

Answer 8

Area of about 3.2-4 mm

Question 9

Surface area advantage of TM over stapes footplate

Answer 9

20:1

Question 10

Effective area of TM

Answer 10

Pars tensa, approx 55 mm

Question 11

Surface area pressure gain

Answer 11

17:1, 25 dB

Question 12

Buckle action

Answer 12

Double velocity of pressure wave, 6 dB

Question 13

Buckle action

Answer 13

Double velocity of pressure wave, 6 dB

Question 14

Ear Canal Reflectance

Answer 14

Acoustic impedance looking into the ear canal

Question 15

Z0 = ρc/A

Answer 15

p= density of air, c= speed of sound, A= cross sectional area of ear canal

Question 16

Impedance Mismatch

Answer 16

Loss of vibration from air to fluid of inner ear

Question 17

I2/I1 = 4Z1Z2/(Z1+Z2)2

Answer 17

Energy immitted

Question 18

Loss of pressure from ME to Inner ear

Answer 18

37 dB

Question 19

TM area

Answer 19

80 mm

Question 20

Footplate of Stapes

Answer 20

Area of about 3.2-4 mm

Question 21

Surface area advantage of TM over stapes footplate

Answer 21

20:1

Question 22

Effective area of TM

Answer 22

Pars tensa, approx 55 mm

Question 23

Surface area pressure gain

Answer 23

17:1, 25 dB

Question 24

Tensor tympani innvervated by

Answer 24

V nerve

Question 25

Buckle action

Answer 25

Double velocity of pressure wave, 6 dB

Question 26

Why is GME lower than theoretical gain?

Answer 26

Force required to stretch ligament and accelerate mass of ossicles, ossicular chain not rigid

Question 27

Stiffness reactance increase

Answer 27

amplitude reduced below resonant freq

Question 28

Mass increased

Answer 28

Response amplitude is reduced above resonant freq

Question 29

Negative ME reactance

Answer 29

up to 800 Hz

Question 30

Positive ME Reactance

Answer 30

5-6 kHz

Question 31

Energy transmission maximal from TM to Cochlea

Answer 31

800-5000 Hz

Question 32

Middle ear pressure

Answer 32

Opposes motion of TM

Question 33

Acoustic Reflex

Answer 33

Response to intense sound stimulation, Bilateral

Question 34

Process of AR

Answer 34

Contraction of Tensor Tympani, Stapedius muscle reflex pulls footplate within oval window

Question 35

AR Absent

Answer 35

patients with pathologies affecting staepedius muscle

Question 36

Stapedius innervated by…

Answer 36

VII nerve

Question 37

Tensor tympani innvervated by

Answer 37

V nerve

Question 38

AR affects which frequencies

Answer 38

Low frequencies, stiffness dominates

Question 39

How much attenuation of AR?

Answer 39

20 dB in lower frequencies

Question 40

Lower intensity obtained for

Answer 40

ipsilateral than contralateral

Question 41

Minimal time for AR

Answer 41

20 ms