LING330: Quiz #2

Question 1

Outer ear (aka auricle)

Answer 1

Consists of:
1- pinna (visible shell of the ear)
2- tympanic membrane (ear canal leading down the eardrum)

Question 2

Function of the pinna

Answer 2

Shell of the ear
Captures sound waves
Aids in localization

Question 3

Function of ear canal

Answer 3

Keep eardrums safely inside our heads (shielded from changes in temp and humidity, and sharp objects)
Acts as a resonator (amplifies sounds especially in 3000hz range, crucial frequency area for speech sounds)

Question 4

Why do we have two ears?

Answer 4

Locate sounds in space

Keep track of source of sound in a noisy enviro

Question 5

Why is there a delay in time and intensity when a sound reaches one ear and the other?

Answer 5

Because they’re separated by a heads width and decrease in intensity is bc “shadow” of the head

Question 6

How does the brain interpret location of sound source?

Answer 6

Sounds echo in folds of pinna in characteristic ways (depending on where sound is coming from)
Interpreted into diffs in phase, intensity, and frequency
Further used to determine location of source

Question 7

Middle ear

Answer 7

Consists of:
1- eardrum (aka tympanic membrane)
2- ossicles (three tiny bones)

Question 8

What are the three ossicles?

Answer 8

1- malleus (touches tympanic membrane; transmits movement to incus)
2- incus (transmits movements to stapes)
3- stapes (transmits movements to oval window and liquid of inner ear)

**hammer, anvil, stirrup

Question 9

Function of ossicles

Answer 9

Connects the eardrum to a second membrane (the oval window of the inner ear)
Transfers sound patterns from one membrane to the other (minimizes reflection of energy, amplifies soft sounds, protects inner ear from very loud sounds)

Question 10

Describe what happens when sound waves travel down the ear canal

Answer 10

1- hit the eardrum
2- eardrum vibrates (mimicking vibration patterns in the sound wave)
**vibration maximized when air pressure on both sides of eardrum is equal (middle ear=air-filled chamber)

Question 11

How is pressure equalization achieved in the middle ear?

Answer 11

Normal circumstances: Eustachian tube creates passageway between middle ear and the mouth (and thus the outside world)

Abnormal circumstances (ex: tube blocked by infection): pressure builds up in middle ear and causes an earache

Question 12

How can you “pop” your ears?

Answer 12

Swallowing/chewing gum activates muscles around Eustachian tube
Can induce exchange of air and release of pressure (aka ears popping)

Question 13

Extreme pressure differences cause what?

Answer 13

Tympanic membrane to rupture

Question 14

Three parts of the ear

Answer 14

Outer
Middle
Inner

Question 15

How is energy transferred in ear?

Answer 15

Eardrum to malleus to incus to stapes to oval window (force increased at each step which amplifies the sound energy)

Question 16

Describe the middle ear reflex

Answer 16

Process that can impede the transfer of energy in very loud sounds
Involuntary contraction of muscles attached to the ossicles (stapedius and tensor tympani) in response to any sound above 80 decibels
Muscle contraction = bones pulled away from membranes
Damps vibrations
Protects oval window from being overly displaced
Protection is only partial so damage is still possible

Question 17

Smallest muscle in the body

Answer 17

Stapedius

Question 18

What is the inner ear encased in?

Answer 18

Temporal bone

Aka thickest part of the skull

Question 19

Two connected parts of inner ear

Answer 19

Vestibular system (for balance)
Cochlea (for hearing)

Question 20

Vestibular system of the inner ear

Answer 20

• three semicircular canals (loops orientated in diff planes at right angles to each other that sense motion in three dimensions)
• utricle + sacchule (sense horizontal and vertical acceleration)
• *both lined with tiny hairs (cilia) and filled with fluid I

Question 21

How does the inner ear maintain balance, fix the gaze and coordinate body motion?

Answer 21

• inner ear organs filled with fluid and lined with tiny hairs called cilia
• cilia attached to nerve fibers
• head moves = motion of fluid makes hairs bend
• triggers nerves to fire
• brain interprets patterns of activation as movement and orientation of the body in space

Question 22

Otoliths

Answer 22

Small crystals of calcium carbonate floating in the fluid in the utricle and saccule which further stimulate the cilia

Question 23

Cochlea

Answer 23

Coiled tube like a snail shell
No bigger than a marble
Divided lengthwise into three parts (scalae):
1- scala vestibuli (on top)
2- scala tympani (on the bottom)
3- scala media (aka cochlear duct; in the middle)
End of cochlea adjacent to middle ear=basal end
Far end of cochlea=apex
Filled with lymphatic fluid
Helicotrema=at the apex of cochlea; connects scala vestibuli and scala tympani

Question 24

The path of sound that leads to hearing

Answer 24

• sound vibrations pass through the eardrum
• pass ossicles
• end up at oval window
• oval window vibrates causing complex pressure waves to move thru lymphatic fluid in the cochlea
• waves move up scala vestibuli
• around helicotrema
• down scala tympani
• at basal end of scala tympani=membrane called round window
• round window expands and contracts as sound waves impact it (acting as a pressure release valve)
• pressure waves move thru cochlea
• cochlear duct becomes deformed
• deformation=hearing !!!

Question 25

What are the two membranes separating the cochlear duct from the scala vestibuli and the scala tympani?

Answer 25

Top (from scala vestibuli): vestibular membrane | Bottom (from scala tympani): basilar membrane

Question 26

What two parts are the basilar membrane touching?

Answer 26

1- connected to protrusion of the temporal bone, a bony shelf that supports the inner ear 2- on top of basilar membrane=tunnel-shaped set of structures known as ORGAN OF CORTI

Question 27

What does the organ of Corti consist of?

Answer 27

A set of hair cells spread out along the cochlear duct Hair cells connected to nerve cells Fine hair cells (stereocilia) protrude from the hair cells

Question 28

What covers the stereocilia?

Answer 28

Tectorial membrane | Described as gelatinous flap

Question 29

What is the organ of Corti bathed in?

Answer 29

Bathed in lymphatic fluid that fills the cochlear duct

Question 30

How is sound interpreted in the cochlea?

Answer 30

- pressure waves reverberate thru scalae - basilar and tectorial membranes move - stereocilia deforms - connected nerves fire - nerve signals carried thru auditory nerve to brain - interpreted as sound

Question 31

How do the stereocilia send their own very low amplitude signals?

Answer 31

They move in delayed response to (or sometimes in absence of) external stimulation Can be heard as acoustic admissions by sensitive microphone placed in the ear Sign of healthy auditory system

Question 32

What part of the ear distinguishes different sounds, and how?

Answer 32

Depends on structure of BASILAR membrane Not the same along its length Basal end=thin and stiff; supported by bony shelf Apex=bony shelf tapers off; basilar membrane is thicker and less stiff Tapered shape creates fine-tuned spectral analysis of the incoming pressure wave Oval window vibrates + sends pressure waves thru the scalae Basilar membrane deforms bc waves Place of greatest deformation depends on frequency Thin end of basilar membrane=responds to high frequencies; thick end=low frequencies; middle=every frequency in between

Question 33

How is complex sound responded to?

Answer 33

Different parts of basilar membrane will respond to the diff component frequencies Amplitude of vibration of basilar membrane at a certain points depends on relative amplitude of frequency in signal (greater amplitude -> greater displacement -> stronger firing of nerves) This organ of Corti creates complete spectral analysis (frequency + amplitude info encoded in message sent to brain)

Question 34

Describe relationship between acoustic frequency and perceived pitch

Answer 34

Bc frequency response not evenly distributed along the basilar membrane, relationship between acoustic frequency and perceived pitch= non linear **more than half basilar membrane devoted to most important frequencies for distinguishing speech sounds

Question 35

What range is the cochlea devoted to?

Answer 35

200-3000 hz Humans can discriminate sounds in this range better than higher or lower **humans can't hear above 20,000 hz but dogs bats and dolphins can

Question 36

Conductive hearing loss

Answer 36

When sound is not being properly transferred from outer to middle to inner ear

Question 37

Neurosensory hearing loss

Answer 37

Inner ear not properly responding to sounds it receives

Question 38

How does congenital deafness (from birth) occur?

Answer 38

Part of the ear doesn't develop normally

Question 39

What are some ways that the ear can be damaged ?

Answer 39

- infections and tumours (inner/middle ear) - some meds cause neural or hair cell damage as side effect - exposure to high amplitude noise - stereocilia damage from over stimulation - aging (structures of ear stiffen over time and stereocilia damaged and lost)

Question 40

How do hearing aids work?

Answer 40

Undo partial hearing loss by boosting amplitude of frequencies to which the ear has lost sensitivity

Question 41

How do cochlear implants work ?

Answer 41

Bypass the ear completely Directly stimulate auditory nerve cells in the way that the cochlea would if it were working Detects level of sound energy at different frequencies and stimulate appropriate nerves accordingly

Question 42

Tympanic membrane

Answer 42

- air right - works like a microphone - protects inner ear from high sounds pressure through partial oscillations

Question 43

Is the tympanic cavity air tight?

Answer 43

No, because if it were, the variations in air pressure would pull/push on the tympanic membrane

Question 44

The Eustachian tubes

Answer 44

- from middle ear to nasopharynx - normally closed, loosely together - can be opened by yawning/swallowing - large air pressure differential between ends=air forced through tube (ex: airplane landing/taking off)

Question 45

How is sound transmitted in the ear?

Answer 45

- the ossicles increase the pressure variations by 22 - as a result of surface area changes and leverage - pressure variations in inner ear are 22x stronger than original pressure of sound waves - amplification of 27 dB

Question 46

What are the three parts of the cochlear tube?

Answer 46

Scala vestibuli Scala tympani Scala media

Question 47

What does the cochlea do?

Answer 47

Transforms sound waves into neural impulses which pass through auditory nerve to brain

Question 48

Two windows of the base of the cochlea

Answer 48

Oval window: where pressure waves reach cochlea (scala vestibuli) Round window (scala tympani): releases sound waves back into tympanic cavity; adjusts pressure inside cochlea

Question 49

Apex of the cochlea

Answer 49

Helicotrema !!! Tip Thinner and wider Softer

Question 50

Path of the scala vestibuli vs the scala tympani

Answer 50

Scala vestibuli: oval window to apex Scala tympani: apex to round window **both are filled with fluid

Question 51

Basilar membrane

Answer 51

``` Separates scalas Where auditory nerve originates Oscillates Transmits pressure waves as transverse surface wave (but movement controlled by the brain) Contains the organ of Corti ```

Question 52

Describe the way sound travels from the tympanic cavity, to the apex of the cochlea and back out into the tympanic cavity?

Answer 52

Through the oval window via the scala vestibuli, to the helicotrema, then back to the oval window via the scala tympani

Question 53

What are the two types of info that the movement of the basilar membrane send to the brain?

Answer 53

Frequency | Amplitude

Question 54

How does the organ of Corti create neural impulses

Answer 54

- linked to auditory nerve - contains outer and inner hair cells ``` 1- sound happens 2- moves outer hair cells 3- amplifies endolymph movement 4- moves stereocilia of inner hair cells 5- change in electrical impulse =neural impulse! ```

Question 55

Outer hair cells

Answer 55

20,000 of them Mechanical amplifier of quieter sounds Touch both basilar and tectorial membranes

Question 56

How do the outer hair cells work ?

Answer 56

1- sound causes basilar membrane to vibrate (causes shearing between basilar and tectorial membranes) 2- moves the stereocilia back and forth 3- movement of the stereocilia cause the cells to shorten then lengthen (electro motile response) 4- amplifies the movement of the endolymph **also regulated by neural impulses from brain and responsible for oto-acoustic transmissions

Question 57

Oto-acoustic transmissions

Answer 57

Outer hair cells are responsible for this Def=an echo caused by the brain sending signals to outer hair cells -causes basilar membrane to move -what newborns are tested for in the hospital

Question 58

Inner hair cells

Answer 58

3,500 of them Covert mechanical movement of basilar membrane into neural impulses (transmit info to brain) Don't touch tectorial membrane (react to changes in endolymph speed caused by outer hair cells)

Question 59

How is pitch interpreted?

Answer 59

Brain interprets pitch of sound based on location of cells sending impulses - basilar membrane (base=thin and stiff, apex=thick and less stiff) - hair cells: shorter and stiffer hairs at base=high frequencies, longer and more flexible hairs at apex=low frequencies

Question 60

How the brain interpret loudness?

Answer 60

Based on number of hair cells activated | Displacement of basilar membrane

Question 61

Does hearing = perception?

Answer 61

No, physical stimulus doesn't equal auditory sensation Non-linear relationship between frequency (acoustic property) and pitch (perceptual correlate) Half of the basilar membrane dedicated to frequencies for speech (200-3000hz, were better at distinguishing these)

Question 62

Sounds and their damage

Answer 62

Typical convo: 60 dB Prolonged exposure causes hearing loss: 85 dB Threshold for pain: 120 dB Maximum MP3 player volume: 110 dB (hearing damage after just 1 hour per day)