Auditory and vestibular systems

Question 1

What are hair bundles made up of?

Answer 1

Made of actin(Stereocilia)

Question 2

Where are hair bundles located?

Answer 2

They sit on top of the hair cells

Question 3

What do hair cells synapse to?

Answer 3

Synapses on to the auditory nerve fibre and projects to the brain

Question 4

What do hair cells over motion of and into what?

Answer 4

Convert motion of the stereocilia into release of neurotransmitter

Question 5

What is the overlying cell matrix in auditory organs?

Answer 5

Tectorial membrane in auditory organs

Question 6

What is the overlying cell matrix in the maculane?

Answer 6

Otoconial membrane in maculane

Question 7

What is the overlying cell matrix in cristae?

Answer 7

Cupula in cristae

Question 8

What can stereocilia be connected via within the bundle?

Answer 8

Within the bundle, stereocilia can be converted via a number of links:

• Lateral links
• Tip links

Question 9

What are examples of lateral link connectors?

Answer 9

• Top connectors
• Shaft connectors
• Ankle links

Question 10

What is the job of lateral link connectors?

Answer 10

Job is to hold bundles together and to move as a unit

Question 11

Where are top links found?

Answer 11

Found at the top of the cilia

Question 12

What does tension in the top link cause and allow?

Answer 12

Tension in the tip link distorts the tip of the stereocilia mechanically
-This allows channels to open and close with cilia movement. Current flows in proportionality

Question 13

How do hair cells work?

Answer 13

• Tip links open ion-channels
• Endolymph is high in K+ and depolarises the cell
• VGCC open
• Ca2+ triggers neurotransmitter release at the synapse
• Post synaptic potential in nerve fibre triggers an action potential

Question 14

What does displacement in cilia cause?

Answer 14

Causes a change in membrane potential

Question 15

What system do most fish and amphibians have along both sides of their body?

Answer 15

Most fish and amphibians have a lateral line system along both sides of their body

Question 16

What do mechanoreceptors provide?

Answer 16

Mechanoreceptors provide information about movement through water or the direction and velocity of water flow

Question 17

What are mechanoreceptors also known as?

Answer 17

Also known as neuromasts

Question 18

Where are superficial neuromasts located?

Answer 18

Superficial neuromast are on the surface of the fish

Question 19

What encases the hair cell bundle and what does it move in response to?

Answer 19

A gelatinous cupula encases the hair cell bundle and moves in response to water motion

Question 20

Where is the auditory system and vestibular system located?

Answer 20

Both located in the inner ear

Question 21

What is the inner ear formed of?

Answer 21

The inner ear is formed of:

• Semicircular canals(Vestibular system)
• Cochlea(Auditory system)

Question 22

What is the vestibular system responsible for?

Answer 22

Responsible for balance and motion in mammals

Question 23

What are semicircular canals used to sense?

Answer 23

Semicircular canals are used to sense rotation

Question 24

What does rotation do?

Answer 24

• Rotation causes fluid motion in semicircular canal

- Hair cells at different canals entrances register different directions

Question 25

What is posterior semicircular canal responsible for?

Answer 25

Responsible for roll

Question 26

What is anterior semicircular canal responsible for?

Answer 26

Responsible for pitch

Question 27

What is Horizontal semicircular canal responsible for?

Answer 27

Responsible for Yaw

Question 28

What are the steps involved in the sensation of rotation?

Answer 28

- Cilia are connected to the gelatinous cupula - Under motion, fluid in the canals lags due to inertia, pulling the cupula in the opposite direction to the rotation of the head - Cilia are displaced, depolarising haircells

Question 29

How are the hair cells arranged in the utricular macula?

Answer 29

Hair cells are arranged in an arching manner

Question 30

What does the utricular macula do as we move in a sideways direction?

Answer 30

As we move in a sideways direction, they pick up motion

Question 31

How are the hair cells arranged in the saccular macula?

Answer 31

Hair cells arranged in up, down, forward and backward direction

Question 32

What can saccular macula detect?

Answer 32

Can detect motion up and down as well as forward and backward

Question 33

What are included in the otolith organs?

Answer 33

- Saccule macula | - Utricular macula

Question 34

How do the otolith organs work?

Answer 34

The hair cells in the otolith organs are topped by a rigid layer of otoconia crystals -Under acceleration the crystal layer is displaced, deflecting the cilia

Question 35

What is the auditory system made up of?

Answer 35

Ear-->Cochlea-->Cochlear nucleus-->Olivary complex-->Lateral lemniscus-->Inferior colliculus-->Medial geniculate body-->Auditory cortex

Question 36

What is sound?

Answer 36

Sound is rapid variation of air pressure

Question 37

What is the wavelength?

Answer 37

Is the distance between 2 peaks in the wave

Question 38

What is the wavelength determined by?

Answer 38

Determined by the rate at which the compression and rarefaction of a wave occur

Question 39

Equation for wavelength

Answer 39

λ=c/f c=speed of sound(344m/s) f=frequency

Question 40

What is the human hearing range in uPa?

Answer 40

2uPa-200000000uPa

Question 41

What is the decible scale and what is its equation?

Answer 41

-Is a log of ratio relative to 2uPa 20log10(amplitude/20)

Question 42

What does the pinna do?

Answer 42

Gathers sound from the environment and funnels it to the eardrum

Question 43

What is the pinna made entirely out of?

Answer 43

Made entirely from cartilage and covered with skin

Question 44

How does the pinna filter sound?

Answer 44

- Flange adds a high frequency amplification - Meatus amplifies low frequencies - Chonca amplifies high frequencies

Question 45

What is microtia?

Answer 45

It is a developmental problem of the pinna

Question 46

How is mictotia scaled?

Answer 46

Severity graded 1-4

Question 47

What is the tympanic membrane also known as?

Answer 47

Also known as the eardrum

Question 48

What does the tympanic membrane do?

Answer 48

Vibrates in response to sound

Question 49

What is the ossicles?

Answer 49

Smallest bone in the human body

Question 50

What are the ossicles made up of and what are they?

Answer 50

Made up of 3 bones: - Malleus - Incus - Stapes

Question 51

What do the ossicles do?

Answer 51

Connect the tympanic membrane to the oval window of the cochlea

Question 52

What is glue ear?

Answer 52

Its where the middle ear fills with fluid which impedes motion of ossicles

Question 53

What does glue ear do?

Answer 53

Reduces middle ear gain, raising hearing threshold

Question 54

What are the 3 chambers to the cochlea?

Answer 54

- Scala vestibuli - Scala media - Scala tympani

Question 55

What is the cochlea?

Answer 55

The cochlea is a fluid filled space canal divided by a flexible membrane

Question 56

What does the basilar membrane do?

Answer 56

Basilar membrane filters sound according to frequency

Question 57

Where does the organ of corti sit?

Answer 57

Sits on top of the basilar membrane within the scala media

Question 58

What is mounted on the organ of corti?

Answer 58

Inner and outer hair cells are mounted on it

Question 59

What does motion of the organ of corti on the membrane cause

Answer 59

Motion of the organ of corti on the basilar membrane causes displacement of sterocilia

Question 60

What do inner hair cells do?

Answer 60

Inner hair cells do transduction

Question 61

What do outer hair cells do?

Answer 61

Outer hair cells are there to act as an amplifier

Question 62

What does an influx of positive ions do to outer hair cells?

Answer 62

Influx of positive ions makes the outer hair cells contract

Question 63

What happens to outer hair cells when ion channels are closed?

Answer 63

When ion channels are closed, prestin has a long conformation and the cell expands

Question 64

What happens to outer hair cells when ion channels are opened?

Answer 64

When ion channels are open, prestin has a short conformation and the cell contracts

Question 65

How does the cochlear amplifier work?

Answer 65

-As the basilar membrane moves upwards, it pushes against the tectorial membrane making the hair cells lean -This allows an influx of positive ions in the outer hair cell -An increase in voltage results in: -Prestin in short conformation state -Outer hair cell contracts -This pulls the basilar membrane towards the tectorial membrane

Question 66

What does the endolymph create?

Answer 66

The high K+ concentration of the endolymph of the scala media creates a 2x amplification

Question 67

What would happen if the endolymph were not K+ rich?

Answer 67

If the endolymph were not K+ rich, then inner hair cell output would be halved making sound quieter