Physiology

Question 1

How does the middle ear structure allow amplification of sound?

Answer 1

High tympanic membrane to ovale window ratio,

Malleus handle is much larger than incus

Question 2

Describe the steps of hearing

Answer 2

1. Sound waves hit tympanic membrane causing it to vibrate
2. Vibrations pass from malleus to incus to stapes to ovale window
3. Vibrations travel through perilymph in the bony labyrinth (otic cavity)
4. Movement through perilymph causes the basilar membrane to vibrate and this moves the hair cells on the organ of corti
5. This causes ion channels to open and depolarisation to occur leading to action potentials
6. APs travel to the spiral ganglion & cochlear nerve
7. Ultimately they reach the posterior superior temporal gyrus

Question 3

What two parts make up the bony labyrinth?

Answer 3

Scala vestiboli & scala tympani

Question 4

How are different frequencies recognised?

Answer 4

Basilar membrane has a variety of fibres that resonate at different frequencies

• short fibres at high frequencies
• long fibres at low frequencies

Question 5

What age can a foetus hear?

Answer 5

18 weeks (from 26 weeks it can respond to sound/voice)

Question 6

At what age can a baby recognise its mothers voice?

Answer 6

3 months

Question 7

At watch age will a baby turn towards sound?

Answer 7

6 months

Question 8

When a baby is 12 months how should their hearing have developed?

Answer 8

Make simple noises, follow instructions and turn to sounds

Question 9

By 2-3 years how should a child’s hearing have developed?

Answer 9

Use three word sentences, rhymes, understands order

Question 10

Which part of the inner ear controls balance?

Answer 10

Semicircular canals, utricle and saccule

Question 11

What is the name for the utricle and saccule?

Answer 11

Otolith Organs

Question 12

In what plane do the otolith organs detect movement?

Answer 12

Horizontal/verticle

Question 13

What do the otolith organs have that allow them to detect motion?

Answer 13

Stereo cilia which project upwards into a gelatinous heavy membrane with otoconia

Question 14

How do otolith organs detect movement?

Answer 14

When you tilt your head the heavy membrane with otoconica is dragged in that direction which stresses the hair cells and thus causes depolarisation and action potentials

Question 15

What nerve are the action potentials produced in the otolith organs passed along?

Answer 15

Vestibular nerve