Vestibular Function

Question 1

The vestibular system is in control of

Answer 1

posture and balance

Question 2

What is the vestibular system?

Answer 2

A sensory system

Series of fluid filled membranous labyrinths which are embedded in the temporal bone

Question 3

Components of the vestibular system

Answer 3

3 semi-circular canals
Utricle
Saccule

Question 4

Sensory hair cells are contained within what parts of the vestibular system

Answer 4

Utricle
Saccule
Ampulla

Question 5

How do the otolith organs (utricle and saccule) work?

Answer 5

They detect linear acceleration and encode information about the position of the head in space

Question 6

Back/front tilt of the head is detected by

Answer 6

the utricle

Question 7

Vertical movement of the head is detected by

Answer 7

the saccule

Question 8

The semi-circular canals detect

Answer 8

rotational acceleration

Question 9

The cupula respond to

Answer 9

movement of the endolymph fluid within the canals

Question 10

The cilia in the gelatinous cupula detect

Answer 10

rotational acceleration

Question 11

What are the types of cilia in the gelatinous cupula?

Answer 11

Single large kinocilium

Progressively smaller stereocilia

Question 12

Distortion of the cilia in the direction of the kinocilium causes

Answer 12

depolarisation and increased discharge off the action potentials in the vestibular nerve

Question 13

Distortion of the cilia away from the kinocilium causes

Answer 13

hyperpolarisation and decreased discharge of action potentials in the vestibular nerve

Question 14

Distortion of the kinocilium allows

Answer 14

the brain to determine movement in time and space

Question 15

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

Answer 15

the maculae

Question 16

The macula in the utricle are oriented on what plane?

Answer 16

Horizontal

Question 17

The macula in the saccule are orientated on what plan?

Answer 17

Vertical

Question 18

Tilt of the head is detected by

Answer 18

the macula in the utricle

Question 19

Do otoliths or endolymph have a greater density?

Answer 19

Otoliths - so are subject to a greater force of gravity

Question 20

What part of the brain co-ordinates the postural muscles required to maintain balance?

Answer 20

Cerebellar centres

Question 21

Projections from the vestibular nuclei on one side project

Answer 21

ipsilaterally, bilaterally and contralaterally to descending motor pathways

Question 22

Vestibular nuclei receive input from

Answer 22

proprioceptors signalling limb and body position, and from neck and eye muscles

Question 23

Vestibular nuclei project via

Answer 23

the thalamus to the cerebral cortex to give perception of movement and body position

Question 24

What is kinaesthesia?

Answer 24

Conscious awareness of where the body is and its movements

Question 25

What tracts are involved in the vestibular system reflexes?

Answer 25

Vestibulocortical | Vestibulospinal

Question 26

Function of tonic labyrinthine reflexes

Answer 26

keep the axis of the head in a constant relationship with the rest of the body using information from maculae and neck proprioceptors

Question 27

How do dynamic righting reflexes work?

Answer 27

Rapid postural adjustments made to stop you falling when you trip Long reflexes involving extension of all limbs

Question 28

How do vestibulo-ocular reflexes work?

Answer 28

Afferents from semicircular canals project and connect to extra ocular nuclei and have strong input to influencing eye movement Visual system sends powerful descending projections which control posture

Question 29

How does static reflex work?

Answer 29

When the head is tilted, eyes intort/extort to compensate so that (over a certain range) the image stays the right way up

Question 30

How does dynamic vestibular nystagmus work?

Answer 30

Series of saccadic eye movements that rotate the eye against the direction of the head and body so that the original direction of gaze is preserved despite head rotating

Question 31

What is vestibular nystagmus?

Answer 31

Rapid, involuntary eye movements related to a damaged vestibular system

Question 32

What can be done to test the horizontal semicircular canal?

Answer 32

Caloric stimulation - outer ear washed with cold or warm fluid

Question 33

Warm fluid causes nystagmus towards

Answer 33

the affected side

Question 34

Powerful maintained stimulation of the vestibular system can give rise to

Answer 34

kinetosis (motion sickness)

Question 35

Kinetosis iis most likely to occur if

Answer 35

visual and vestibular inputs to the cerebellum are in conflict