Middle Ear

Question 1

Middle ear Muscles

Answer 1

Tensor tympani and the stapedius muscle

Question 2

Middle ear ligaments

Answer 2

Superior ligament, lateral ligament, anterior ligament, posterior ligament

Question 3

Eustachian tube

Answer 3

Connect middle ear space to the nasopharynx

Question 4

Chorda Tympani

Answer 4

Branch of the 7th cranial nerve
Facial nerve
Responsible for taste reception to the tongue

Question 5

Middle ear space

Answer 5

Bound from eardrum (lateral wall) to the end of the stapes (medial wall)
There is a bulging of the inner ear on medial wall called the promentory
Temporal bone (makes up of inferior wall)
Epitympanic recess (attic) - makes up of the superior boundary

Question 6

Tympanic Membrane

Answer 6

Ossicles

Malleus, incus, stapes

Question 7

Eustachian tube

Answer 7

Connected to middle ear

Allow air pressure to equalize on both side of the ear drums

Question 8

Ear infection

Answer 8

Adenoids produce white blood cells when you have a cold
Swelling in adenoids occurs
Adenoids sit at the base of the Eustachian tube so the can’t open
Pressure doesn’t equalize
Air vacuum are fluid fills space
Bacteria grow in the fluids

Question 9

Myringotomy

Answer 9

A hole is cut into the ear drum to drain fluids

Question 10

Middle ear physiology

Answer 10

The eardrum is sensitive to pressure. When there is a fluctuation in pressure in front of the eardrums, it vibrates in a very complex manner
Stapes footplate is embedded into the oval window

Question 11

Gregor Von Bekesy -1941

Answer 11

Won a Nobel prize for his work in describing how the ear works
Said when the ossicles are vibrating, the footplate rock back and forth on the window.
Proven incorrect. The stapes footplate only rock back and forth at high intensities

Question 12

Tonndorf and Khanna -1972

Answer 12

Used more sophisticated technology called “time-averaged holography”
Found that the eardrum vibrates in a very complex manner, and that the vibrate is the most complex when a signal comes in at a high frequency or high amplitude.

Question 13

Oval window

Answer 13

Is the membrane into the cochlea

Question 14

Guinan and Peake - 1967

Answer 14

Studies cat’s middle ear
Found that cats have similar middle ears to humans
Said stapes footplate move in and out of the oval window like a piston

Question 15

Impedance

Answer 15

Opposition to the flow of energy
All matter has its own characteristic impedance
We lose approx. 30-36 dbSPL
No middle means sounds would go through fluid instead of air, thus losing energy

Question 16

Acoustic Reflex

Answer 16

The bilateral contraction of the stapedius muscle in response to a loud sound

Question 17

Acoustic Reflex Arc

Answer 17

Outer ear ➡️ middle ear ➡️ inner ear ➡️ cranial nerve VIII ➡️ cochlear nucleus ➡️ superior olivary complex ➡️ Motor nucleus or cranial nerve VII ➡️ middle ear

Question 18

Tensor Tympani

Answer 18

Attaches to the manubrium of malleus

Question 19

Stapedius Muscle

Answer 19

Attach to the neck of the stapes
Muscle contracts, the stapes is pulled
This stiffen the middle ear system
Add impedance by keeping the ossicle from vibrating as easily
Contract when load sound is present “acoustic reflex”

Question 20

Three main middle are function

Answer 20

1) transformer - matching impedances.
2) transducer - change energy from one form to another. Energy is change from acoustic to mechanical
3) band-pass filter - able to set the middle ear into motion at low SPLs ( 800 Hz)

Question 21

Transformer jobs

Answer 21

1) area ratio difference between eardrums and the stapes footplate
➡️force is transmitted from large to small area, pressure is increased
2) lever action of the ossicles
➡️small effect
Mass of the ossicles is position in such a way to take advantage if the leverage
Small force applied to the malleus give a much larger force from the incus