Physiology of Hearing and Balance

Question 1

What is the normal human hearing range?

Answer 1

20-20,000 Hz

Question 2

Which part of ear acts as receiver of sound

Answer 2

External ear

Question 3

Which part of ear acts as mechanical amplifier of sound

Answer 3

Middle ear

Question 4

Explain the amplification mechanism of the middle ear

Answer 4

1. Tympanic membrane: OW ratio is 18:1 –> higher pressure
2. Ossicle decrease in size which concentrates energy (malleus:incus ratio)

Question 5

What is the theoretic mechanical gain in energy from the amplifier mechanism in middle ear?

Answer 5

34 dB

Question 6

What acts as the transducer/analyser of sound in the ear?

Answer 6

Curved spiral lamina

Question 7

Describe the coiled tubes of liquid in cochlea

Answer 7

Scala media (endolymph) suspended in between scala tympani & scala vestibuli (perilymph)

Question 8

What is the functional unit of transduction mechanism in ear?

Answer 8

Inner hair cells in the Organ of Corti
(takes pressure wave and transforms into electrical energy)

Question 9

Where is oval window and round window located?

Answer 9

Cochlea and middle ear

Question 10

What is the function of oval and round windows?

Answer 10

Permit transmission of pressure waves in enclosed canal + vibration of the basilar membrane

Question 11

Which cranial nerve gets stimulated after depolarization of the tectorial membrane?

Answer 11

CN VIII (vestibulo-cochlear nerve)

Question 12

What is the function of eustachian tube?

Answer 12

keeps ear at atmospheric pressure

Question 12

Electrical signals culminate in the _____ of the _____ within the ______ gyrus

Answer 12

1. Brodman areas 41-42
2. primary auditory cortex
3. superior temporal

Question 13

Dysfunction of eustachian tube leads to ____

Answer 13

negative middle ear pressure

Question 13

What muscles open eustachian tube?

Answer 13

tensor veli palatini
levator palatine

Question 14

Name the otolith organs

Answer 14

utricle, saccule

Question 15

Name the specialised sensory structures found on hair cells of inner ear?

Answer 15

kinocilium, stereocilia

Question 16

What are otoconia

Answer 16

calcium carbonate crystals found in the gelatinous matrix within the otolithic organs (specifically, the utricle and saccule)

Question 17

What is the function of otoconia

Answer 17

lend weight and due to gravity – brain perceives position and movement when tilting the head or linear motion

Question 18

What is the vestibulo-ocular reflex?

Answer 18

The deflection caused by the movement of perilymph.
‘Bending’ causes stereocilia to deflect.

Question 19

How does right vestibular damage cause vertigo?

Answer 19

• Lack of firing in the right ear (right vestibular nerve damage)
• Increased firing (++) in left ear
• Brain interprets that as turning left, causing vertigo

Question 20

Vestibulospinal tract is responsible for _____?

Answer 20

posture

Question 21

Medial longitudinal fasciculus & ocular muscles are responsible for ____

Answer 21

gaze stabilisation

Question 22

Medial lemniscus and thalamus to cerebrum is involved in ____

Answer 22

awareness