15b. Inner Ear, Hearing, Vestibular Function

Question 1

What is presbycusis?

Answer 1

Age-related bilateral hearing impairment

Unable to hear frequencies below 1500 Hz

Question 2

What are the risk factors for presbycusis?

Answer 2

Noise exposure
Ototoxins
Infections
Smoking, hypertension, vascular disease, diabetes
Immunological disorders
Genetics (mtDNA)

Question 3

What is sensorineural presbycusis?

Answer 3

Degeneration of the cilia on hair cells of organ of Corti or loss of cochlear nerve fibres

Question 4

What is conductive presbycusis?

Answer 4

Stiffening of the basilar membrane of the cochlea or ossicles

Question 5

What is metabolic presbycusis?

Answer 5

Atrophy of the stria vascularis

Loss of resting potential of endolymph

Question 6

What is the treatment for presbycusis?

Answer 6

Ear protection, avoid loud noises
Assistive devices
Lip reading
Amplification devices and cochlear implants

Question 7

What is the function of hearing aids?

Answer 7

Amplify waves in the outer ear and auditory canal

Question 8

What are the parts of a hearing aid?

Answer 8

Microphone, amplifier, speaker

Question 9

What is the use of both a hearing aid and a cochlear implant called?

Answer 9

Electric Acoustic Stimulation

Question 10

What is the function of a cochlear implant?

Answer 10

Capture and convert sound to electrical signals

Goes to electrode array in cochlea via a stimulator

Question 11

What type of energy does the vestibular system rely on?

Answer 11

Hydraulic

Question 12

What is the name of the sensory epithelium of the ampulla of the semi-circular canals?

Answer 12

Crista ampullaris

Question 13

What does the crista ampullaris detect?

Answer 13

Angular acceleration (rotation)

Question 14

What are the utricle and saccule collectively known as?

Answer 14

Otolith organs

Question 15

What do the otolith organs detect?

Answer 15

Position of the head with respect to gravity (linear acceleration)

Question 16

What does the superior semi-circular canal detect?

Answer 16

Up and down movements

Question 17

What does the posterior semi-circular canal detect?

Answer 17

Head tilting to one shoulder

Question 18

What does the horizontal semi-circular canal detect?

Answer 18

Head turning side to side

Question 19

What is the name of the gelatinous mass that surrounds the crista ampullaris?

Answer 19

Cupula

Question 20

What happens to the endolymph when the semi-circular canals rotate?

Answer 20

Endolymph stays still

Pushes against cupula which bends stereocilia of hair cells

Question 21

What happens when the stereocilia are pushed against the kinocilium?

Answer 21

Influx of K+ and Ca+ via mechanoceptors causes depolarisation
Release of glutamate activates the vestibular nerve

Question 22

What happens in the opposite ear to the one with the activated vestibular nerve?

Answer 22

Stereocilia bend away from the kinocilium

Hair cells hyperpolarise

Question 23

What are the Otolith Organs?

Answer 23

Membranous labyrinths within the vestibule

Question 24

What is the saccule connected to?

Answer 24

Scala media

Question 25

What is the utricle connected to?

Answer 25

Semi-circular ducts

Question 26

What is the name of the sensory epithelium in the otolith organs?

Answer 26

Macula

Question 27

What is the macula composed of?

Answer 27

Supporting cells, sensory hair cells, vestibular dark cells

Question 28

What surrounds the macula?

Answer 28

Otolithic membrane

Question 29

Describe the make-up of the otolithic membrane

Answer 29

Gelatinous | Contains calcium carbonate crystals (otoliths, otoconia)

Question 30

What plane do the macular hair cells project into in the utricle?

Answer 30

Vertical

Question 31

What does the utricle respond to?

Answer 31

Horizontal linear acceleration | Head tilt

Question 32

What plane do the macular hair cells project into in the saccule?

Answer 32

Horizontal

Question 33

What does the saccule respond to?

Answer 33

Vertical linear acceleartion | Low frequency vibration

Question 34

What is the resting potential of the endolymph?

Answer 34

80mV

Question 35

What is the resting potential of the perilymph?

Answer 35

6mV

Question 36

What transport proteins maintain the resting potential of the endolymph?

Answer 36

Na/K NKCC1 (Na, K and 2Cl into cell) K+ leak channel

Question 37

What is motion sickness?

Answer 37

Continual movement of endolymph after head movement has stopped and visual cues tell the brain you are stationary

Question 38

What is Méniere's disease?

Answer 38

Unilateral fluid imbalances in inner ear due to a build-up of endolymph or a reduction of blood flow to the ear

Question 39

What are the risk factors for Meniere's disease?

Answer 39

Abnormal immune response Viral infection Genetics

Question 40

What are triggers for Meniere's disease?

Answer 40

Stress, overwork, fatigue, emotional distress, migraine Autoimmune disorders Pressure changes High salt, caffeine, alcohol

Question 41

What are the symptoms of Meniere's disease?

Answer 41

``` Feeling of fullness in ear Low-pitched tinnitus Hyperacusis (more sensitive to changes in sound) Sensorineural hearing loss Nystagmus, vertigo, ataxia Nausea and vomiting Tumarkin's otolithic crisis ```

Question 42

What is Tumarkin's otolithic crisis?

Answer 42

Spontaneous feeling of being pushed | Patient will fall to the ground without notice

Question 43

What diet changes can help with Meniere's disease?

Answer 43

Reduce salt, caffeine, alcohol and smoking

Question 44

What lifestyle changes can help with Meniere's disease?

Answer 44

Counselling and physical therapy

Question 45

What medications can help with Meniere's disease?

Answer 45

Anxiolytics Antiemetics Diuretics Steroid injection into inner ear (reduces inflammation) Gentamycin injection into inner ear (purposefully damages to stop vertigo)

Question 46

What surgeries can help with Meniere's disease?

Answer 46

Endolymphatic sac surgery | Endolymphatic duct blockage

Question 47

What is the procedure for endolymphatic sac surgery?

Answer 47

Bone is removed and shunt placed in endolymphatic sac to drain fluid

Question 48

What is the procedure for endolymphatic duct blockage?

Answer 48

Bone removed and clip placed on endolymphatic sac to prevent fluid build-up in rest of inner ear