Vestibular System Flashcards by Ell Loukily

What are the 3 main inputs of the vestibular system?

Visual
Proprioceptive
Vestibular info

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What are the main outputs of the vestibular system?

Reflexes that allow you to be maintain stable posture, gaze and stop you from falling over:
Ocular reflex
Postural control

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Where is the vestibular organ found?

Posterior area of inner ear

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What does the vestibular organ do?

Senses rotation and movement of the head

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How many semicircular canals are there and describe them

There are 3: anterior, posterior and lateral
They have an ampulla on one side and are connected to the utricle
They do not have otoliths

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What is the biggest cilium on vestibular hair cells called?

Kinocilium

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Where are hair cells in the vestibular cells found?

On all 5 organs:
utricle
saccule
lateral, posterior and anterior semicircular canals

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How do the cilia on hair cells allow depolarisation?

They are moved by endolymph when the head moves

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What are the otolith organs? Where are their cells located?

Utricle and saccule

Their cells are located on the maculae

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What are otolith?

Carbonate crystals on top of the hair cells that helps their deflection

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How are cells placed in the utricle?

Horizontally

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How are cells placed in the saccule?

Vertically

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How is the macula structured?

Contains hair cells, a gelatinous matrix and the otoliths on top

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In the semicircular canals where is the hair located?

On the crista in the ampulla

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What are the 3 planes in the semicircular canals?

Anterior and posterior (that form a 90 degree angle)

Lateral which are horizontal to the others

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Where do primary afferents end?

Vestibular nuclei (in brainstem) and cerebellum

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What do the vestibular nuclei have projections to?

Spinal cord
Nuclei of the extraocular muscles (eye movements)
Cerebellum (to get feedback)
Centres for cardiovascular + respiratory control

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What is the role of the vestibular cortex? (3)

To detect and inform about head movements
To keep images fixed in the retina during head movements
Postural control

How many potentials do hair cells have?

Resting
Excitation
Inhibition

Describe the resting potential of hair cells

Has a basal discharge to the nerve

What happens to nerve discharge during excitation?

Increases

When do hairs move towards to kinocilium?

During excitation: depolarisation of cell

When do hairs move away from the kinocilium

During inhibition: hyperpolarization of cell

What type of movement do otolith organs detect?

Linear acceleration and tilt

Out of the utricle and saccule, which is sensitive to horizontal movement and which to vertical movement?

Utricle: horizontal movement Saccule: vertical movement

What movement do semicircular canals detect?

Angular acceleration

How do semicircular canals work?

In pairs- anterior from one side will work with posterior from other side Cupulla moves and displaces hair cells (capulla surrounds hair cells) Output signal on vestibulocochlear nerve is velocity

What does the vestibulo-ocular reflex do?

Keeps images fixed in the retina when you move your head Eyes move in the opposite direction to head movement but at same velocity and amplitude Connection between vestibular nuclei and ocular nuclei

What does the vestibulo spinal reflex do?

If moving and about to loose balance it stops you from falling by causing certain muscles to contract

Where do motor neurons of the lateral vs medial tract go to in terms of the vestibulospinal reflex?

``` Lateral= go to limb muscles Medial= go to neck and back muscles ```

What is assessed in a vestibular system assessment?

``` Anamnesis (history) Posture and gait Cerebellar function Eye movements Vestibular tests ```

What is the main symptom of balance disorder?

Dizziness or vertigo | Vertigo is spinning but dizziness is a subjective term

What do peripheral vestibular disorders affect?

Labyrinth or CN VIII

What do central vestibular disorders affect?

CNS: Brainstem or cerebellum

What are the main acute vestibular disorders?

Vestibular Neuritis (‘labyrinthitis’), stroke

What is the main intermittent vestibular disorder?

Benign Paroxysmal Positional Vertigo (BPPV)

What are the main recurrent vestibular disorders?

Meniere’s Disease (hearing loss will be in one ear), Migraine

What are the main progressive vestibular disorders?

Schwannoma vestibular (VIIIth nerve), Degenerative conditions (MS)

What else may dizziness indicate other than vestibular disorders?

``` Heart disorders Presyncopal episodes Orthostatic hypotension Anaemia Hypoglycaemia Psychological Gait disorders ```

How is hearing loss characteristic in Menieres?

Only occurs in one ear

What is the vestibular cortex?

It's not one specific area since many inputs and integrators are involved- many cortical areas participate

Where is the main processing centre of the vestibular cortex?

In the parietal lobe in the parieto-insular vestibular cortex

What vestibular tests can be carried out?

Caloric test Video head impulse test Vestibular evoked myogenic potential (measures connections between vestibular system and neck muscles) Rotation test

What imaging techniques can be used to assess the vestibular system?

CT, MRI