15a. Inner Ear, Hearing and Vestibular Function

Question 1

What is the name of the eardrum?

Answer 1

Tympanic membrane

Question 2

What is connected to the tympanic membrane?

Answer 2

Malleus

Question 3

Name the auditory ossicles

Answer 3

Malleus
Incus
Stapes

Question 4

What is the stapes connected to?

Answer 4

Oval window

Question 5

What does the eustachian tube connect the middle ear to?

Answer 5

Nasopharynx

Question 6

What are the functions of the eustachian tube?

Answer 6

Equalise pressure

Drain fluid from the middle ear into the throat

Question 7

What is impedance?

Answer 7

Resistance to movement

Question 8

How is impedance combatted in the ear?

Answer 8

Energy from the large surface area of the tympanic membrane is concentrated onto the oval window
Lever action of the ossicles amplifies vibration

Question 9

What comprises the vestibular apparatus?

Answer 9

Utricle
Saccule
3 semi-circular canals

Question 10

What information is received by the vestibular apparatus?

Answer 10

Balance
Co-ordination
Head positions

Question 11

What lobe does information from the vestibular apparatus go to?

Answer 11

Temporal

Question 12

What is mechanotransduction?

Answer 12

Sound waves are converted to nerve impulses by the displacement of fluid

Question 13

What does pushing in of the oval window cause?

Answer 13

Movement of fluid in the scala vestibuli

Question 14

What fluid is found in the scala vestibuli?

Answer 14

Perilymph

Question 15

What cochlear labyrinth is connected to the round window?

Answer 15

Scala tympani

Question 16

What fluid is found in the scala media/ cochlear duct?

Answer 16

Endolymph

Question 17

What is contained in the scala media?

Answer 17

Organ of Corti

Question 18

What separates the scala vestibuli from the scala media?

Answer 18

Reissner’s membrane

Question 19

Which membrane separates the scala media from the scala tympani?

Answer 19

Basilar membrane

Question 20

What is the composition of perilymph?

Answer 20

Similar to CSF
High Na+
Low K+

Question 21

What is the composition of endolymph?

Answer 21

Low Na+

High K+

Question 22

What is found in the lateral wall of the cochlea?

Answer 22

Stria vascularis

Question 23

What makes up the stria vascularis?

Answer 23

Capillaries and marginal cells

Question 24

What is the function of marginal cells?

Answer 24

Maintain the resting potential of endolymph by maintaining high K+

Question 25

What membrane lies above the hair cells of the Organ of Corti?

Answer 25

Tectorial membrane

Question 26

What happens when hair cells in the Organ of Corti are bent against the tectorial membrane?

Answer 26

Cilia bend Influx of K+ Depolarisation causes opening of voltage gated Ca++ channels Glutamate is released

Question 27

What does amplitude of a sound wave correspond to?

Answer 27

Volume

Question 28

What is the normal hearing threshold?

Answer 28

0-90dB

Question 29

What volume causes pain?

Answer 29

130dB

Question 30

What does frequency of a sound wave correspond to?

Answer 30

Pitch

Question 31

How are different frequencies differentiated from by the Organ of Corti?

Answer 31

Location of the hair cells along basilar membrane of the scala media Low: Close to helicotrema High: Close to base

Question 32

What is the normal audible frequency threshold?

Answer 32

20-20,000 Hz

Question 33

What is the frequency of speech?

Answer 33

100-3400 Hz

Question 34

What hearing test is used to test frequency?

Answer 34

Pure tone audiometry

Question 35

What is an audiogram?

Answer 35

Plot of thresholds for amplitude and frequency

Question 36

What is sensorineural deafness?

Answer 36

Degeneration of hair cells in the Organ of Corti and/or cochlear nerve fibres

Question 37

What are the causes of sensorineural deafness?

Answer 37

Loud sound Vascular lesion Ototoxicity

Question 38

What can cause ototoxicity?

Answer 38

Aminoglycosidases: antibiotics and loop diuretics

Question 39

What is conductive deafness?

Answer 39

Impaired sound transmission in external or middle ear

Question 40

What are the causes of conductive deafness?

Answer 40

Wax Foreign body Perforated tympanic membrane Infection

Question 41

What test is used to differentiate between sensorineural and conductive deafness?

Answer 41

Weber and Rinne

Question 42

What does the Weber test detect?

Answer 42

Unilateral loss | Patient must know which ear is affected

Question 43

What result is positive for conductive hearing loss in the Weber test?

Answer 43

Patient hears tuning fork louder in the affected ear

Question 44

What result is positive for sensorineural hearing loss in the Weber test?

Answer 44

Tuning fork is louder in healthy ear

Question 45

What is the Rinne test used to evaluate?

Answer 45

Air and bone conduction

Question 46

How is the Rinne test conducted?

Answer 46

Tuning fork is placed on the mastoid process until the patient can no longer hear it Quickly place near auditory canal Compare times it took to hear

Question 47

What is a normal/positive Rinne result?

Answer 47

Air conduction> bone conduction

Question 48

What is a negative Rinne/ conductive loss result?

Answer 48

BC> AC | Due to blockage of air entering ear

Question 49

What is the result for sensorineural hearing loss in the Rinne test?

Answer 49

AC> BC but decreased duration of hearing AC