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BB2 > Vestibular System > Flashcards

Vestibular System Flashcards

1
Q

What is the function of the vestibular system?

A

Maintains balance, posture and spatial orientation

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2
Q

What are the 3 receptor systems of the vestibular system?

A

Eyes
General proprioception via muscles/tendons/joints and cutaneous receptors
Vestibular receptors in the ear

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3
Q

What is the role of the spinothalamic tract?

A

Basic sensations:

crude touch, pain and temperature

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4
Q

What is the role of the DCML?

A

Complex sensations:

vibration, conscious proprioception, discriminative touch

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5
Q

What is the membranous labyrinth?

A 
Vestibular part (semi-circular canal)
Auditory part (cochlea)
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6
Q

What is the endolymph?

A

Fills the membranous labyrinth

Endocochlear potential formed (positive voltage) due to high potassium and low sodium

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7
Q

What is the perilymph?

A

Within bony labyrinth
Surrounds membranous labyrinth
High sodium low potassium

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8
Q

What do the semi-circular canals consist of?

A

Anterior, lateral and posterior canals

All at right angles to each other

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9
Q

How do we know which plane our head rotates in and the strength of this rotation?

A

The endolymph shifts within the canals

- speed/volume of endolymph movement

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10
Q

What are the otolithic organs?

A

Utriculus

Sacculus

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11
Q

What is the role of the kinocilium?

A
  • when endolymph bends kinocilium causing depolarisation or hyperpolarisation
  • Kinocilium contains potassium channels that opens in response to movement
  • depolarisation: releases neurotransmitter (glutamate) causing excitation
  • hyperpolarisation: stop neurotransmitter release
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12
Q

Where is the kinocilium?

A

In the vestibular apparatus arranged in size order with long at the top

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13
Q

What happens within the ampulla of the semi-circular ducts?

A
  • crista ampularis
  • embedded in gelatinous gel
  • senses angular acceleration and deacceleration
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14
Q

What happens within the utricular and saccular maculae?

A

Membranous sacs
Contain otoliths which compress the cilia and respond to gravitational forces
- utricles get polarised towards the striola so it divides the macula into medial and lateral halves
- saccules get polarised away from the striola so it divides macula into anterior and posterior halves

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15
Q

What is the striola?

A

Curved ridge running through middle of sensory epithelium

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16
Q

What is the pathway of the vestibular-ocular reflex?

A

Vestibular nerve afferents -> central vestibular neurons -> extraocular motor neurons -> eye muscles

17
Q

How do eyes stay fixed on an object whilst the head moves right?

A
  • endolymph causes hyperpolarisation on the left inhibiting left medial rectus and right lateral rectus
  • depolarisation on the right stimulates right medial rectus and left lateral rectus
  • means eyes move towards the left and stay focused on object
18
Q

What is nystagmus?

A

A form of vestibulo-ocular reflex

  • combination of initial slow rotation followed by fast flick back
  • rapid and accurate eye movements
19
Q

Is nystagmus normal or abnormal?

A

Optokinetic (fixation) and rotational nystagmus - normal

Spontaneous nystagmus - abnormal as damage to vestibular apparatus/brainstem/cerebellum

20
Q

Which nerves are responsible for motor control of eye movements?

A
  • CN III
  • CN IV (superior oblique)
  • CN VI (lateral rectus)
21
Q

What is the central pathway from the vestibular labyrinth?

A

Afferents from vestibular labyrinth to vestibular nuclei

22
Q

Where are the vestibular nuclei?

A

Rostral medulla and pons

23
Q

What are the vestibular nuclei?

A
  • superior vestibular and medial vestibular nucleus

- lateral vestibular and inferior vestibular nucleus

24
Q

What are the afferents to the superior vestibular and medial vestibular nucleus?

A

From the ampulla of the semi-circular canals

25
Q

What are the afferents to the lateral vestibular and inferior vestibular nucleus?

A

From the maculae of the utricle and saccule

26
Q

What is the ascending vestibular pathway?

A

Ascending axons of the neurons in superior vestibular nucleus enter medial longitudinal fasciculus

27
Q

How does the vestibular apparatus project to the cerebellum?

A

Afferents reach flocculonodular lobe:

  • directly from vestibular apparatus
  • indirectly from medial and inferior vestibular nuclei
28
Q

How does the cerebellum project to the vestibular apparatus?

A

Lateral vestibular nucleus receives excitatory and inhibitory signals from the cerebellum

29
Q

What is the role of the innervating ocular muscles?

A
  • superior vestibular nucleus and medial vestibular nucleus travel to the oculomotor and trochlear travel to them along reticular formation
30
Q

What are the vestibulocortical projections?

A

Superior vestibular and lateral vestibular communicate with the cerebral cortex

31
Q

What are the vestibulospinal projections?

A

Lateral vestibular nucleus and medial vestibular form:

  • lateral vestibulospinal tracts (antigravity muscles) from lateral nucleus
  • medial vestibulospinal tracts (head and neck muscles) from medial nucleus
32
Q

What does equilibrium depend on?

A
  • signals coming from vestibular apparatus (positioning and movements of head must be continuous with those of eyes and body)
33
Q

What are the main 3 vestibular pathologies?

A
  • kinetosis
  • Meniere’s disease
  • benign paroxysmal positional vertigo
34
Q

What is kinetosis?

A

motio sickness

- difference between visually perceived movement and sense of movement

35
Q

What is Meniere’s disease?

A

Of inner ear causing vertigo episodes

- otoliths go into semi-circular canals and shouldn’t be there

36
Q

What is BPPV?

A

Benign paroxysmal positional vertigo:

brief episodes of mild to intense vertigo

37
Q

How do you clinically examine balance disorders?

A

Eye movements
Caloric texting
hallpike manoeuvre

38
Q

How do you test for balance disorders?

A 
Clinical examination
vestibular testing (videonystagmography and electronystography)
Vestibular imagine (MRI)

BB2 (31 decks)

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