Vestibular System

Question 1

Vestibular system function

Answer 1

Maintaining balance, posture and special orientation

Question 2

Vestibular system 3 receptors

Answer 2

Eyes
General proprioceptive and cutaneous receptors
Vestibular receptors in ear

Question 3

Spinothalamic

Answer 3

Crude touch
Pain
Temperature

Question 4

Dorsal columns

Answer 4

Vibration
Proprioception
Discriminative touch

Question 5

Membranous labyrinth

Answer 5

Inner ear
Vestibular part (semi-circular canal)
Auditory part (cochlea)

Question 6

Endolymph

Answer 6

Fills membranous labyrinth
High potassium
Low sodium
–> Endocochlear potential, +ve voltage within ML

Question 7

Perilymph

Answer 7

Within bony labyrinth surrounding membranous labyrinth

High sodium, low potassium

Question 8

Semi-circular canals

Answer 8

Anterior Canal- Vertical
Lateral Canal- Horizontal
Posterior Canal- Vertical
Canals are at right angles of each other

Question 9

Endolymph movement

Answer 9

When we move head, endolymph shifts within the canals
–> allows us to know which plane our head is rotating along
Speed/volume of endolymph gives us information of strength of rotation

Question 10

Where do semi-circular ducts end

Answer 10

In Ampulla

Question 11

Otolithic Organs

Answer 11

Utriculus

Sacculus

Question 12

Hair cells within vestibular apparatus

Answer 12

Long kinocilium on top
–> when hair bends, either depolarises or hyperpolarises depending on direction
Depolarization- release neurotransmitter (glutamate) –> excites
Hyperpolarization- stops neurotransmitter release

Question 13

Kinocilium MOA

Answer 13

Contain potassium channels that open in response to movement

Question 14

Ampulla of semi-circular ducts

Answer 14

AKA Crista ampularis
Embedded in gelatinous gel
Senses angular acceleration and deacceleration

Question 15

Utricular + Saccular maculae

Answer 15

Membranous sacs

Contain Otoliths- crystals that compress cilia continuously + responsive to gravitational forces

Question 16

Striola

Answer 16

Curved ridge that runs through the middle of the macula

Orientate stereocilia

Question 17

Utricles

Answer 17

Hair cells polarised (excited) towards striola

Striola divides macula into medial and lateral halves

Question 18

Saccules

Answer 18

Hair cells polarised away from the striola

Striola divides each macula into anterior/posterior halves

Question 19

Semi-circular hair cells

Answer 19

Kinetic sensitivity
Sensitive to head rotation
Angular acceleration
Complementary bilateral signalling

Question 20

Otolithic Organ hair cells

Answer 20

Utriculus- horizontal
Sacculus- vertical
Gravity
Tilt of head
Linear acceleration

Question 21

Vestibulo-Ocular reflex

Answer 21

Vestibular-nerve afferents –> central vestibular neurones –> extraocular motor neurones –> eye muscles

Question 22

Move head to the right

Answer 22

Endolymph causes hyperpolarisation on left, which inhibits left medial rectus + right lateral rectus
Causes depolarisation on right, stimulating right medial rectus and left lateral rectus
–> eyes move left, staying on object they were fixed on

Question 23

Nystagmus

Answer 23

Form of vestibulo-ocular reflex
Rapid and accurate eye movements
Initial slow rotation followed by fast flick back

Question 24

Opokinetic (fixation) and rotational nystagmus

Answer 24

Normal

Question 25

Spontaneous nystagmus

Answer 25

Abnormal | Damage to vestibular apparatus, brainstem or cerebellum

Question 26

Superior vestibular and medial vestibular nucleus

Answer 26

Afferents from ampulla of semi-circular canals

Question 27

Lateral vestibular and inferior vestibular nucleus

Answer 27

Afferents from ampulla of semi-circular canals

Question 28

Ascending vestibular pathway

Answer 28

Ascending axons of neurones in SVN enter MLF rostral to abducens nucleus

Question 29

Superior + Medial Vestibular Nuclei travel to..

Answer 29

Oculomotor and trochlear nucleus along the reticular formation

Question 30

Lateral vestibulospinal tract

Answer 30

Antigravity muscles

Question 31

Medial vestibulospinal tracts

Answer 31

Head/neck muscles

Question 32

Sens of equilibrium

Answer 32

Depends on signal coming from vestibular apparatus

Question 33

Kinetosis

Answer 33

Motion sickness

Question 34

Meniere's disease

Answer 34

Disease of inner ear Episodes of vertigo Otoliths go into semi-circular canals where they are not supposed to be

Question 35

Benign paroxysmal positional vertigo

Answer 35

brief episodes of mild to intense vertigo

Question 36

Balance disorders clinical exam

Answer 36

Eye movements caloric testing Hallpike manoeuvre- lower head to table + turn to one side, watch for nystagmus + dizziness--> if anything, ear pointing to floor is affected