Vestibular Function

Question 1

What does the vestibular system control?

Answer 1

Posture and balance

Question 2

Where is the vestibular system found?

Answer 2

Inner ear

Question 3

Where are labyrinths embedded?

Answer 3

In the temporal bone

Question 4

How many semi-circular canals are there?

Answer 4

3

Question 5

What are the semi-circular canals all connected to?

Answer 5

Saccule

Question 6

At what angle are the semi-circular canals to each other?

Answer 6

Right angles

Question 7

What is the swelling at the base of the semi-circular canals called?

Answer 7

Ampulla

Question 8

What do the ampulla contain?

Answer 8

Sensory hair cells

Cristae

Question 9

What is the utricle?

Answer 9

Swelling at the anterior base of the ampulla

Question 10

What is the saccule?

Answer 10

Swelling below the utricle

Question 11

What are the utricle and saccule collectively known as?

Answer 11

Otolith organs

Question 12

What do otolith organs detect?

Answer 12

Linear acceleration and encode information about the position of the head in space

Question 13

What is back/front tilt detected by?

Answer 13

Utricle

Question 14

What is vertical movement detected by?

Answer 14

Saccule

Question 15

Where is rotational movement detected?

Answer 15

Semi circular canals

Question 16

Where are the sensory cells of semi-circular canals located?

Answer 16

Ampulla

Question 17

What are the sensory receptors in the ampulla called?

Answer 17

Cristae

Question 18

What is located at the base of the cupula?

Answer 18

Sensory hair cells

Question 19

What are cupula?

Answer 19

Gelatinous structure that stretch across the entire width of the ampulla

Question 20

What do the cilia or hair cells synapse directly with?

Answer 20

Sensory neurons of the vestibular nerve

Question 21

What is CN VIII?

Answer 21

Vestibulocochlear nerve

Question 22

What movement do the hair cells in the gelatinous material of the ampulla detect?

Answer 22

Rotational acceleration

Question 23

Does endolymph move automatically with skull rotation?

Answer 23

No fluid takes a while to move

Question 24

Does endolymph more as quickly as the skull?

Answer 24

No

Question 25

Does the ampulla move instantly with head movement ?

Answer 25

Yes because it it embedded in the skull

Question 26

What happens to endolymph when the head moves?

Answer 26

Initially it does not move because of its intertia | Then produces a drag in the opposite direction which bends the cupula and the cilia embedded in it

Question 27

If you rotate constantly and the endolymph catches up what happens if you stop suddenly?

Answer 27

Endolymph continues to move and spin | Creating the a continous sense of movement and dizziness

Question 28

What is vertigo?

Answer 28

The perception of movement in the absence of movement

Question 29

What are the 2 types of cilia hair cells in the ampulla?

Answer 29

Kinocilium | Stereocilia

Question 30

What does distortion of the cili in the direction of the kinocilium cause?

Answer 30

Depolarisation and increased discharge of AP in vestibular nerve

Question 31

What does distortion of cilia away from the kinocilium cause?

Answer 31

Hyperpolarisation and decreased discharge of AP in the vestibular nerve

Question 32

Where does much of the cilia movement sensory information integrated?

Answer 32

In the cerebellum

Question 33

What is the sensory apparatus of the utricle and saccule collectively known as?

Answer 33

Maculae

Question 34

Which plane are the macula in the utricle orientated?

Answer 34

Horizontal plane

Question 35

Which plane are the macula in the saccule orientated?

Answer 35

Vertical plane

Question 36

What are the cilia in the maculae called?

Answer 36

Kinocilium | Stereocilium

Question 37

What is embedded in the otolith membrane?

Answer 37

crystals called otoiths

Question 38

Where is tilt of the head detected?

Answer 38

By the macula in the utricle

Question 39

What gives orientation of the head when lying down?

Answer 39

Macula in the saccule (vertical plane)

Question 40

What does backwards tilt of the head cause?

Answer 40

Moves the otolith crystals in the direction of the kinocilium causing depolarisation and increase in AP

Question 41

What does forwards tilt of the head cause?

Answer 41

Moves the otolith crystals away from the kinocilium cause hyperpolarisation and decrease in AP

Question 42

Why do the macula not have the same mechanisms with endolymph?

Answer 42

Because the bones in the skull do not move alot with linear or vertical movements

Question 43

What is kinaesthesia?

Answer 43

Being aware of where you body is in time and space

Question 44

Where do vestibular nuclei receive input from?

Answer 44

Proprioceptors signalling limb and body position | Also from neck and eye muscles

Question 45

Where do vestibular nuclei project via?

Answer 45

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

Question 46

What descending tracts are involved in vestibular system reflexes?

Answer 46

Vestibulocortical | Vestibulospinal tracts

Question 47

What is the tonic labryinthine reflex?

Answer 47

Keep the axis of the head in a constant relationship with the rest of the body. Use information from maculae and neck proprioceptors.

Question 48

What is the dynamic righting reflexes?

Answer 48

Rapid postural adjustments that are made to stop you falling when you trip Involves extension of all of the limbs

Question 49

What is the vestibulor-ocular reflexes?

Answer 49

Strong associations is evident between the vestibular apparatus , the visual apparatus and postural control Afferents from the semi-circular canals project and connect (within the vestibular nuclei) to afferent fibres travelling to the extraocular nuclei and thus have strong input to influencing eye movement.

Question 50

What is the static reflex?

Answer 50

The intorsion and extorsion of the eyes to compenstae for tilt of the head

Question 51

What is kinetosis?

Answer 51

Motion sickness

Question 52

What can powerful maintained stimulation of the vestibular system cause?

Answer 52

Motion sickness

Question 53

What are the symptoms of motion sickness?

Answer 53

``` Nausea Vomiting Decrease in BP Sweating Pallor Dizziness ```

Question 54

What causes motion sickness

Answer 54

If the visual and vestibular system inputs to the cerebellum are in conflict

Question 55

What can lesions of the brain stem lead to?

Answer 55

Nystagmus at rest