4.6 Hearing and Equilibrium

Question 1

What are the three parts of the ear?

Answer 1

1. External Ear
2. Middle Ear
3. Inner Ear

Question 2

What is the external ear?

Answer 2

• pinna, external auditory meatus and tympanum (tympanic membrane)
• transmits airborne sound waves to fluid-filled inner ear
• amplifies sound energy

Question 3

What is the middle ear?

Answer 3

• Transmits airborn sound waves to fluid filled inner ear

- amplifies sound energy

Question 4

What is the inner ear?

Answer 4

houses two different sensory systems

1. Cochlea:
   - contains receptors for conversion of sound waves into nerve impulses, which makes hearing possible
2. Vestibular Apparatus
   - necessary for sense of equilibrium

Question 5

What is hearing?

Answer 5

the neural perception of sound energy

Question 6

What two aspects are involved in hearing?

Answer 6

1. Identification of the sound (what)

2. Localization of the sound (Where)

Question 7

What are sound waves?

Answer 7

Travelling vibrations of air

-consist of alternate regions of compression and rarefaction of air molecules

Question 8

What are the three properties of sound waves?

Answer 8

1. Pitch (tone)
2. Intensity (volume)
3. Timbre (quality)

Question 9

What is Pitch?

Answer 9

• depends on frequency of air waves
• greater frequency produces higher pitch
• human ear detects 20-20,000 frequency

Question 10

What is intensity?

Answer 10

volume
-Depends on amplitude of air waves or pressure differences between a high-pressure region of compression and a low-pressure region of rarefaction

*greater amplitude = louder sound

Question 11

What is timbre?

Answer 11

-determined by overtones (additional frequencies superimposed on top of the fundamental pitch or tone)

Question 12

What is the tympanic membrane?

Answer 12

In external ear

• vibrates when struck by sound waves
• outside of eardrum is exposed to atmospheric pressure
• inside eardrum exposed to atmospheric pressure via eustachian tube

Question 13

What happens in the middle ear?

Answer 13

vibrations are transferred through ossicles to oval window

Question 14

What are the ossicles?

Answer 14

three smallest bones

• malleus
• incus
• stapes

Question 15

What is the oval window?

Answer 15

Entrance into fluid-filled cochlea

Question 16

Sound pressure of airborne sound waves is amplified by two mechanisms:

Answer 16

1. surface area of the tympanic membrane

2. lever action of ossicles

Question 17

What do waves in the cochlear fluid cause?

Answer 17

motion of the basilar membrane

Question 18

What is the basilar membrane?

Answer 18

forms floor of the cochlear ducts

• has organ of Corti
• Receptive hair cells are bent as membrane is moved up and down

Question 19

What are hair cells?

Answer 19

Receptors for sound

• one row of inner hair cells: -Tranform mechanical forces of sound (cochlear fluid vibration) into electrical impulses of hearing (action potentials)
• 3 rows of outer hair cells: actively change length in response to changes in membrane potential

Question 20

What structure protrudes from each hair cell? What does it do?

Answer 20

stereocilia

-contact the tectorial membrane