Exam #2

Question 0

Where are other places in the ear, that we can find/ measure a simple periodic wave? (They all mimic a sound wave)

Answer 0

TM, malleus, incus, stapes footplate, basilar membrane, and (if it were possible) hair cell movement.

Question 1

What three things are determined by impedence?

Answer 1

1. Mass
2. Stiffness
3. Friction of the medium

Question 2

What is the equation for The Area Trick or Condensation Effect?

Answer 2

Pressure (E) = Force (F)/ Area (A)

Question 3

The labyrinth contains what two sensory systems?

Answer 3

Vestibular System & Auditory System

Question 4

The membranous labyrinth portion of the cochlea consists of what two membranes?

Answer 4

Basilar Membrane & Reissner’s Membrane

Question 5

The tympanic membrane is composed of what three layers?

Answer 5

The Epithelium, The Mucous Membrane, & The Fibrous Layer

Question 6

What are the six surfaces of the tympanic cavity, what are they?

Answer 6

Superior, Inferior, Anterior, Posterior, Medial & Lateral

Question 7

Where is the superior surface of the Tympanic Cavity, and what structures are located on the surface?

Answer 7

The superior surface means “above” or “on top”.

Structures: NONE!!

Question 8

Where is the lateral surface of the Tympanic Cavity, and what structures are located on the surface?

Answer 8

Lateral means “Away from midline of the body”.
Structures: The lateral wall is made up by the tympanic membrane with a section of bone superior to it in the attic portion of the middle ear.

Question 9

Where is the posterior surface of the Tympanic Cavity, and what structures are located on the surface?

Answer 9

Posterior means
Structures: 1) A prominence parallel in height to the oval window called the Pyramidal Eminence.
2) The stapedius muscle is housed/and passes through the pyramidal eminence into the middle ear.

Question 10

Where is the medial surface of the Tympanic Cavity, and what structures are located on the surface?

Answer 10

Medial means “closer to midline of the body”
Structures: 1) Oval window
2) Round Window
3) Stapes Footplate
4) Annular Ligament (connects the stapes footplate to the oval window)
5)Promontory (The first basal turn is jutting into the promontory creating the bulging effect)
6) Facial Nerve ( 7th Nerve- Superior to the oval window hidden by small bony ridge.)
7) Chorda tympani (branch of the facial nerve passes through the ossicles.)

Question 11

Where is the inferior surface of the Tympanic Cavity, and what structures are located on the surface?

Answer 11

Inferior means “lowest portion”, “below”, “bottom”, “under” or “beneath”.
Structures: NONE!! (Separates the middle ear from the jugular vein)

Question 12

Where is the anterior surface of the Tympanic Cavity, and what structures are located on the surface?

Answer 12

Anterior means the “nearer the front, especially situated in the front of the body or nearer to the head”
Structures:
1. cochleariform process (pyramid/”volcano”)
2. tendon of the tensor tympani muscle (Runs along eustachian tube)
3. Eustachian Tube

Question 13

Where is the eustachian tube located?

Answer 13

Anterior surface of the tympanic cavity.

Question 14

What muscles participate in the acoustic reflex?

Answer 14

1) Tensor Tympani

2) Stapedius

Question 15

What are the three functional subsystems of the auditory system?

Answer 15

1) Conductive
2) Sensorineural
3) Central

Question 16

What are the functions of the Eustachian Tube?

Answer 16

1) Equalize air pressure on both sides of the TM.
2) Allows for the air supply that is essential to the metabolism of the tissues of the middle ear.
3) Aids in drainage of middle ear secretions into the nasopharynx.

Question 17

What portion of the malleus attaches to the tympanic membrane?

Answer 17

Manubrium

Question 18

What is the functions of the Conductive System?

Answer 18

Transmission & Impedence Matching

Question 19

What does it mean to say that there is an impedence mismatch between the outside air and the inner ear?

Answer 19

A sound wave is generated in air, low impedence medium, and transmitted to the fluid-filled cochlea, a high impedence medium. When the transfer of of sound is made from the low impedence of the middle ear to the high impedence of the fluid, a great deal of energy must be lost.

Question 20

What are the functions performed by the sensorineural system?

Answer 20

Transducer, Frequency Analyzer, & Transmission

Question 21

How does the middle ear overcome impedence mismatch?

Answer 21

With the Area Trick or the Lever Trick.

Question 22

How large is the impedence mismatch?

1) Expressed as a ratio:
2) Expressed on a dB scale:

Answer 22

1) 1/1000th (?)

2) -30 dB or 30 dB of loss

Question 23

What does the superior wall separate in the tympanic cavity?

Answer 23

It separates the middle ear from the brain.

Question 24

What does the inferior wall separate in the tympanic cavity?

Answer 24

It separates the middle ear from the jugular vein.

Question 25

How does the eustachian tube of an infant compare to an adult? Why are these anatomical differences important?

Answer 25

A child's eustachian tube is significantly shorter, wider, and straighter than an adults and therefore is much more susceptible to disruption of normal functioning, as well as to the spread of infection from the nose and throat, to the middle ear. (Hence, gravity does not help with drainage, therefore BAM otitis media)

Question 26

What gap at the apex of the cochlea allows the fluid in the vestibular canal to communicate with the fluid in the tympanic canal.

Answer 26

Helicotrema

Question 27

What material is a fatty substance that coats the fibers of some but NOT all neurons therefore speeding up the transmission of neural signals.

Answer 27

Myelin Sheath

Question 28

The peripheral auditory system consists of everything from the pinna up to and including what?

Answer 28

The 8th Auditory Nerve

Question 29

What do neurons have in common with toilets?

Answer 29

They both have refractory periods (a disappointing flush)

Question 30

The Central Auditory system consists of structures in the what?

Answer 30

Brain stem & Auditory cortex

Question 31

What is characteristic frequency?

Answer 31

(Best Frequency) The sharp dip in each tuning curve represents the LOWEST threshold and therefore the frequency at which the neuron is MOST sensitive.

Question 32

What does it mean to say that the auditory pathway exhibits tonotopic organization?

Answer 32

The relationship that exists on the auditory nerve between the CF and the physical location of the nerve fiber along the basilar membrane correspond.

Question 33

What anatomical structure lies immediately above the superior surface of the tympanic cavity.

Answer 33

Epitympanic recess (Attic) AND Brain, dura, meninges.

Question 34

What effects do thee contraction of the tensor tympani and the stapedius muscles have on the structures of the middle ear?

Answer 34

1) Stiffens the Tympanic membrane | 2) Stiffens the ossicular chain.

Question 35

What is the area of the TM?

Answer 35

0.594cm^2

Question 36

What is the area of the stapes footplate?

Answer 36

0.032cm^2

Question 37

How do you do the Area Trick/ Condensation Trick??

Answer 37

dB= 20log*(0.594/0.032) = 20log*(18.6) = 20(1.27) =25.4 dB (This is how many dB we will gain back after the Area Trick/Condensation Effect)

Question 38

Malleus is how much longer than the incus lever arm?

Answer 38

30%

Question 39

The Lever Trick

Answer 39

The lever ratio is 1.3 : 1.0 dB= 20log*(1.3) = 20 * (0.11) = 2.3 dB

Question 40

The total amount of decibels restored by the Area Trick and the Lever Trick=

Answer 40

(25.4 dB + 2.3 dB) = 27.7 dB

Question 41

Give an example of of the difference between force and pressure:

Answer 41

A good example would be a dull knife and a sharp knife. The sharp knife has a smaller area while the dull knife has a larger area. Both can be pushed down to cut meat with the same amount of force, but only the sharp knife will cut through the steak due to a smaller area. It is important because the auditory system uses this same idea in the condensation effect. Sound is collected over a large area of the tympanic membrane and is transferred to an area 13 times smaller the stapes footplate. This causes a pressure to increase at the oval window, since the original force has remained unchanged, but the area has been reduced.

Question 42

Frequency Response

Answer 42

``` F(1) = C/4*L F(2)= F(1)*3 F(3)= F(1)*5 ```

Question 43

What does it mean to say that the auditory system is a spectrum analyzer?

Answer 43

It means that the sensorineural mechanism of the auditory system breaks a complex sound into it's individual frequency components. On the basilar membrane of the cochlea, high frequency components are interpreted near the base, where as, low frequency components are interpreted near the apex.

Question 44

How many auditory nerve fibers are there? (per cochlea)

Answer 44

30,000 (~10 nerve fibers per IHC)

Question 45

The cochlea contains roughly how many channels?

Answer 45

3,000-3,500

Question 46

What is transduction?

Answer 46

Mechanical vibration that is converted into a series of impulses on the auditory nerve.

Question 47

In depth explanation of transduction.

Answer 47

1) Vibration of basilar membrane will cause cilia to pivot at the base. 2) Sheering of cilia results in flow of electrical current through the hair cell called receptor current. 3) Receptor current stimulates release by the hair cell of neurotransmitter chemicals. 4) The uptake of neurotransmitter chemicals by dendrites in the 8th nerve fiber connected to the base of the hair cell, stimulates all-or-none action potential in the nerve fiber.

Question 48

Transduction links:

Answer 48

Are filaments connecting cilia of different heights.

Question 49

What attaches the basilar membrane to the cochlea?

Answer 49

Spiral Ligaments

Question 50

Ganglion

Answer 50

Collection of cell bodies.

Question 51

Most auditory nerve fibers synapse on

Answer 51

IHCs

Question 52

Most auditory nerve fibers are

Answer 52

afferent

Question 53

What specific component of the hair cell channel is ressponsible for transduction?

Answer 53

Inner hair cells

Question 54

A hair cell channel consists of

Answer 54

1 IHC & 3 OHCs

Question 55

Whether a nerve fiber fires or not depends on:

Answer 55

1) Time elapsed since the last time it fired. | 2) The strength of the stimulus. (AKA how much neurotransmitter chemicals is dumped)

Question 56

Whether a nerve fiber fires is:

Answer 56

Probablistic: All-or-none

Question 57

Important hair cell properties:

Answer 57

1) graded/continuous (analog) | 2) half-wave rectification

Question 58

What is the largest amount of voltage you can have in your body?

Answer 58

140mv

Question 59

What do the V & A systems have in common?

Answer 59

Common Fluid System Hair Cell Motion Detectors Innervation

Question 60

Synchrony Theory

Answer 60

When nerve impulses are in sync from separate hairs.