Vestibular Physiology

Question 1

What are the utricle and saccule collectively known as?

Answer 1

Otolith organs

Question 2

Where are the sensory cells of the semicircular canals?

Answer 2

Ampulla - swellings at the base of the bony canals

Question 3

What are the sensory receptors?

Answer 3

Cristae - capula and cilia

Question 4

What do the cristae respond to?

Answer 4

Movement of endolymph within the canals

Question 5

Cilia embedded in the capula synapse directly with which nerve?

Answer 5

Vestibular nerve (CN8, VIII)

Question 6

What allows the detection of movement?

Answer 6

Ampulla moves instantly because it’s embedded in the skull

Inertia of the endolymph produces drag and bends the capula in the opposite direction to movement

Question 7

Two types of cilia of the hair cells

Answer 7

Single large kinocilium

Set of progressively smaller stereocilia

Question 8

What causes increased depolarisation and discharge of APs in the vestibular nerve?

Answer 8

Distortion of the cilia towards the kinocilium

Question 9

What causes hyperpolarisation and decreased discharge of APs in the vestibular nerve?

Answer 9

Distortion of the cilia away from the kinocilium

Question 10

The sensory apparatus of the utricle and saccule are collectively known as?

Answer 10

The maculae

Question 11

The macula in the utricle are orientated in?

Answer 11

The horizontal plane

Question 12

The macula in the saccule are orientated in?

Answer 12

The vertical plane

Question 13

The maculae also have a set of cilia which protrude into

Answer 13

The otolith membrane (gelatinous mass)

Question 14

Embedded in the otolith membrane are CaCO₃ crystals called?

Answer 14

Otoliths

Question 15

Otoliths move in response to?

Answer 15

Gravitational forces, otoliths are more dense than the otolith membrane

Question 16

Static reflex?

Answer 16

Eyes intort/extort when you tilt your head

Question 17

Dynamic vestibular nystagmus?

Answer 17

Series of saccadic movements that rotate the eye against the direction of rotation of the head and body (e.g. slowly rotating roundabout)
When the eye reaches the end of its range of motion, flicks quickly back to start position

Question 18

What determines the direction of the nystagmus?

Answer 18

The direction of the rapid flick back (matches the direction of rotation)

Question 19

COWS?

Answer 19

Cold - Opposite

Warm - Same

Question 20

Powerful maintained stimulation of the vestibular system can give rise to?

Answer 20

Kinetosis (motion sickness)

Question 21

When is motion sickness most likely to occur?

Answer 21

When visual and vestibular system inputs to the cerebellum are in conflict.

Question 22

What is vertigo?

Answer 22

The perception of movement in the absence of movement. May also be nystagmus
Causes gross impairment of posture and balance

Question 23

Labyrinthitis?

Answer 23

Acute interference with normal vestibular function as a result of infection

Question 24

What are the symptoms of labyrinthitis?

Answer 24

All ANS symptoms and vertigo

Question 25

Ménière’s disease?

Answer 25

Over production of endolymph causing increased pressure (cause unknown)

Question 26

What are the symptoms of Ménière’s disease? (4)

Answer 26

Vertigo
Nausea
Nystagmus
Tinnitus

Question 27

Inner ear can be susceptible to damage from drugs such as?

Answer 27

Streptomycin

Question 28

Can chronic vestibular impairment be compensated?

Answer 28

Compensated by the visual system, learning circuits set up in the cerebellum
Problems occur of visual information cannot be used

Question 29

What can lead to nystagmus at rest?

Answer 29

Lesion of the brain stem