The auditory system

Question 1

What is a sound wave?

Answer 1

Vibrating particles passing vibrations onto the next particle

Question 2

What is the peak of a sound wave?

Answer 2

Compressed air

Question 3

What is the trough of a sound wave?

Answer 3

Rarefied air

Question 4

What is frequency?

Answer 4

Number of compressed or rarefied patches of air that pass our ears each second

Question 5

What is the units of frequency?

Answer 5

Hertz (Hz)

Question 6

What is intensity?

Answer 6

Air pressure difference between peaks and troughs (amplitude)

Question 7

What are the units of intensity?

Answer 7

Decibels (dB)

Question 8

What kind of scale is decibels?

Answer 8

Logarithmic

Question 9

What is the range of hearing for humans?

Answer 9

20 Hz to 20 000 Hz

Question 10

What are the 3 main regions of the ear?

Answer 10

• Outer
• Middle
• Inner

Question 11

What is included in the outer ear?

Answer 11

Pinna to the tympanic membrane

Question 12

What is the tympanic membrane?

Answer 12

Eardrum

Question 13

What is the pinna?

Answer 13

Part of the ear that you can see

Question 14

What is included in the middle ear?

Answer 14

Tympanic membrane to the oval window (air filled)

Question 15

What is included in the inner ear?

Answer 15

Cochlea

Question 16

What is the function of the outer ear?

Answer 16

Convolutions allow for sound localisation in the vertical plane

Question 17

What are the 3 smallest bones in the body?

Answer 17

Ossicles

Question 18

What are the names of the ossicles?

Answer 18

• Hammer (also malleus)
• Anvil (also incus)
• Stirrup (also stapes)

Question 19

Where are the ossicles located?

Answer 19

Between the tympanic membrane and oval window

Question 20

Which ossicle is attached to the tympanic membrane?

Answer 20

Hammer (malleus)

Question 21

Which ossicle is attached to the oval window?

Answer 21

Stirrup (stapes)

Question 22

What is the connection like between the malleus and incus?

Answer 22

Rigid

Question 23

What is the connection like between the incus and stapes?

Answer 23

Flexible

Question 24

What is the purpose of the ossicles?

Answer 24

To concentrate the sound when it is transmitted to the cochlea

Question 25

Why does the sound need to be concentrated by the ossicles?

Answer 25

- Cochlea is fluid-filled which has a higher impedance than air - Without the ossicles, not enough force would be generated by the sound to cause sufficient fluid movement in the cochlea - Ossicles overcome the impedance of the cochlear fluid

Question 26

What happens when the tympanic membrane is pushed inwards?

Answer 26

- Malleus moves down which pushes incus forward, stapes pushes into oval window causing fluid to move through the cochlea - Fluid pushes out through the round window

Question 27

What happens when the tympanic membrane is pulled outwards?

Answer 27

- Malleus moves up which pulls incus backwards, stapes pulls back so oval window moves out and cochlear fluid comes towards oval window - Round window pulls inwards

Question 28

What is the apex of the cochlea?

Answer 28

Helicotrema

Question 29

What are the 3 compartments of the cochlea?

Answer 29

- Scala vestibuli - Scala media - Scala tympani

Question 30

Which direction does fluid move through the scala vestibuli?

Answer 30

From the oval window to the apex

Question 31

Which direction does fluid move through the scala tympani?

Answer 31

From the apex to the round window

Question 32

What is the fluid inside the scala vestibuli and scala tympani in the cochlea?

Answer 32

Perilymph

Question 33

Which sections of the ear are filled with perilymph?

Answer 33

Scala vestibuli and scala tympani

Question 34

What is the fluid inside the scala media?

Answer 34

Endolymph

Question 35

Which section of the cochlea is filled with endolymph?

Answer 35

Scala media

Question 36

What is special about endolymph?

Answer 36

High K+ content

Question 37

What do the hair cells rest on?

Answer 37

Basilar membrane

Question 38

What is the organ of Corti?

Answer 38

Auditory organ containing the basilar membrane and hair cells

Question 39

What are the 2 kinds of hair cells?

Answer 39

Outer and inner

Question 40

Which section of the basilar membrane detects high frequency sounds?

Answer 40

Bottom

Question 41

Which section of the basilar membrane detects low frequency sounds?

Answer 41

Apex

Question 42

Which part of the basilar membrane is stiff and narrow?

Answer 42

Bottom

Question 43

Which part of the basilar membrane is floppy and wide?

Answer 43

Apex

Question 44

What is the tonotopic map of the cochlea?

Answer 44

Base of the basilar membrane responds to high frequency sounds and the apex responds to low frequency

Question 45

What is the membrane which is on top of the hair cells?

Answer 45

Tectorial membrane

Question 46

Which hair cells transduce auditory information?

Answer 46

Inner hair cells

Question 47

What is the structure of the stereocilia on the hair cells?

Answer 47

3 rows of stereo cilia in ascending size

Question 48

What happens when the smaller stereocilia are pulled towards the taller stereocilia?

Answer 48

Hair cell depolarises

Question 49

What happens to the hair cells when the stapes pulls outwards?

Answer 49

- Basilar membrane moves upwards - Stereocilia pushed towards tallest one - Hair cell depolarises

Question 50

What happens when the taller stereocilia are pushed towards the smaller stereocilia?

Answer 50

Hair cell hyperpolarises

Question 51

What happens to the hair cells when the stapes pushes inwards?

Answer 51

- Basilar membrane moves downwards - Stereocilia pushed towards smallest one - Hair cell hyperpolarises

Question 52

Which section of the cochlea is the organ of Corti in?

Answer 52

Scala media

Question 53

What is the function of inner hair cells?

Answer 53

Transduce sound

Question 54

What connects the stereocilia?

Answer 54

Tip links

Question 55

How does high intensity sound cause hearing loss?

Answer 55

Breaks tip links between stereocilia

Question 56

What is the mechanoelectrical transducer channel called?

Answer 56

TMC1

Question 57

What happens in the hair cell when the short cilia are pulled towards the tall ones?

Answer 57

- Pulling of the tip links opens TMC1 - K+ from endolymph enters the hair cell and causes depolarisation - Voltage-gated Ca2+ channels open - Ca2+ causes exocytosis of vesicles containing glutamate - Glutamate binds to receptors on primary afferent neuron

Question 58

Which neurotransmitter is used in the auditory system?

Answer 58

Glutamate

Question 59

What happens in the hair cell when the tall cilia are pushed towards the small ones?

Answer 59

- TMC1 is closed - Hair cell becomes hyperpolarised - No Ca2+ so no glutamate released

Question 60

What is the function of outer hair cells?

Answer 60

Amplify lower intensity sounds (quiet) by amplifying the movement of the cochlear fluid/basilar membrane

Question 61

How are outer hair cells electromotile?

Answer 61

When hyper/depolarised they become shorter/longer