Chapter 7 - The Ear, Hearing and Balance

Question 1

What are the 3 sections of the ear and what are they filled with?

Answer 1

Outer - Air

Middle - Air

Inner - Liquid

Question 2

What are the components of the outer ear and their purpose?

Answer 2

The pinna - funnelling sound into the auditory canal.

The auditory canal - direction sound to the tymphatic membrane (ear drum)

Question 3

What separates the outer and middle ear?

Answer 3

The tymphatic membrane (ear drum)

Question 4

What are the components of the middle ear and what are their purpose?

Answer 4

The ossicles (Maleus (Hammer), Incus (Anvil), Stapes (Stirrup)) - To transmit vibrations from the tymphatic membrane to the oval window of the cochlea.

The eustachian tube - a tube that connects the middle ear to the throat and allows for pressure equalisation between the middle ear and the outside.

Question 5

What are the components of the inner ear and what are their purpose?

Answer 5

The cochlea - Transmits vibrations, from the oval window, into electrical impulses sent to the brain via the auditory nerve.

Question 6

What 2 barriers separate the middle ear and the inner ear?

Answer 6

The oval window and the round window.

Question 7

What is the name of the system responsible for hearing?

Answer 7

The auditory system

Question 8

What is the name of the system responsible for balance?

Answer 8

The vestibular system

Question 9

What is the membrane in the middle of the cochlea called that is responsible for creating the electrical impulse sent to the brain?

Answer 9

The corti membrane

Question 10

What 2 ways can vibrations be recieved by the inner ear?

Answer 10

Through the middle & outer ear

From the skull by bone conduction

Question 11

What is the human hearing frequency range.

Answer 11

20 - 20000Hz

Question 12

What is sound intensity/loudness measured in?

Answer 12

dB

Question 13

What increaase in dB is equivelant to doubling intensity?

Answer 13

3dB

Question 14

What increaase in dB is equivelant to doubling loudness?

Answer 14

10dB

Question 15

What kind of frequency sounds will have more of an adverse effect on a pilot?

Answer 15

high frequency sounds

Question 16

What can exposure to extremely high levels of sound cause?

Answer 16

Acoustic trauma

Question 17

What dB range when heard continuously can cause hearing loss?

Answer 17

90+dB

Question 18

What dB of sound can cause discomfort?

Answer 18

100dB

Question 19

What dB of sound can cause pain?

Answer 19

140dB

Question 20

What is Noise Induced Hearing Loss (NIHL), and what can it lead to?

Answer 20

Damage to the sensitive membrane in the cochlea due to over exposure to noice above 90dB.

Leads to permanent hearing loss of particular frequency.

Question 21

What can affect the damage to hearing for a pilot?

Answer 21

Intensity of sounds

Frequency of sounds (highest worst)

Duration of exposure

Proper use of headset

Question 22

What is conductive hearing loss?

Answer 22

Defect of the mid or outer ear which prevents sound from being transmitted to the inner ear.

Question 23

What can cause conductive hearing loss?

Answer 23

Mid ear infection, otitis media (glue ear)

Osteosclerosis

Physical damage to ear drum

Excessive accumilation of wax

Damage to ossicles in mid ear.

Question 24

What is presbycusis?

Answer 24

Hearing loss due to degeneration of the hearing system due to age.

High frequencies tend to go first.

Question 25

What is Tinnitus?

Answer 25

A constant ringing/humming/buzzing noise due to damage in auditory system.

Question 26

What is barotrauma?

Answer 26

Where the pressure between the middle and outer ear cannot be equilised due to a block eastachian tube.

Question 27

Why should you never go flying if you suspect that you can't clear your ears?

Answer 27

You may suffer from barotrauma.

Question 28

When is barotrauma most likely to be worst?

Answer 28

During rapid descent.

Question 29

What is the Valsava method?

Answer 29

equilising pressure between mid and outer ear by trying to blow through nose while holding it shut, forcing the eustachian tube open.

Question 30

What is the information obtained from the vestibular system used for?

Answer 30

Posture, balance and stabilising vision.

Question 31

What does the vesitbular system comprise of and what are their purpose?

Answer 31

Otoliths (Utricle and Saccule) - Linear accelaration detection Semi circular canals - Angular accelaration detection.

Question 32

How do the semicircular canals detect angular accelaration?

Answer 32

Inside each canal is a liquid and at the end of each canal is a bulb formation called an Ampulla. Inside the Ampulla is a Cupula, which has little hair cells sticking out of it. When a rotation occurs, the liquid flows in the canals and thus displaces the hair cells on the cupula, which is interpretted as a rotational movement.

Question 33

What are the names of the 3 different semicircular canals?

Answer 33

Lateral - z axis Posterior - y axis Anterior - x axis

Question 34

How do the Otoliths detect linear accelaration?

Answer 34

The Utricle, positioned horizontally, and the Saccule, positioned vertically, each have an array of hair like sensors which then have tiny crystals mounted of top of them, also called otoliths. When a linear accelaration occurs, these top heavy cells deflect and this is interpreted as an accelaration. They also detect tilt.

Question 35

What are the limits of the vestibular system?

Answer 35

It assumes linear accelarations of 1g relative to the body are the effect of gravity Can only detect initial rotational movement Has threshold below which externam stimulation do not trigger action potentials.

Question 36

What is motion sickness?

Answer 36

Disorientation regarding an objects relative movement

Question 37

What is visual habituation?

Answer 37

A decrease in response of the visual system neurons to motion detection due to prolonged exposure (eg. when driving for a long time of a motorway.)

Question 38

What are the symptoms of motion sickness and what can be done to remedy them?

Answer 38

Symptoms: Nausea; Hyperventillation Remedies: Keep head still; Open air vents; Steady progressive maneovres; Medication may help but always consult an aviation doctor before self medication.

Question 39

What effect does alcohol have on the ear and how long can it's effects last?

Answer 39

It reduces the SG of the liquid in the inner ear, leading to erroneous signals in the otoliths and semicircular canals. They can persist for up to 3 days,