Vestibular System Flashcards
What are the 3 main inputs of the vestibular system?
Visual
Proprioceptive
Vestibular info
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
Where is the vestibular organ found?
Posterior area of inner ear
What does the vestibular organ do?
Senses rotation and movement of the head
How many semicircular canals are there and describe them
There are 3: anterior, posterior and lateral
They have am ampulla on one side and are connected to the utricle
What is the biggest cilium on vestibular hair cells called?
Kinocilium
Where are hair cells in the vestibular cells found?
All 5 organs
How do the cilia on hair cells allow depolarisation?
They are moved by endolymph when the head moves
What are the otolith organs?
Utricle and saccule
What are otolith?
Crystals on top of the hair cells that help them move
How are cells placed in the utricle?
Horizontally
How are cells placed in the saccule?
Vertically
What ion is endolymph rich in?
Potassium
In the semicircular canals where is the hair located?
On the crista in the ampulla
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
Where do primary afferents end?
Vestibular nuclei and cerebellum
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
What is the role of the vestibular cortex?
To detect and inform about head movements
To keep images fixed in the retina during head movements
Postural control
Where is the vestibular cortex found?
Many cortical areas participate
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
When do hairs move away from the kinocilium
During inhibition
What type of movement do otolith organs detect?
Acceleration without angle
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
What does the vesticulo ocular reflex do?
Keeps images fixed in the retina when you move your head
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 assessed in a vestibular system assessment?
Anamnesis Posture and gait Cerebellar function Eye movements Vestibular tests
What is the main symptom of balance disorder?
Dizziness or vertigo
What do peripheral vestibular disorders affect?
Labyrinth or CN VIII
What do central vestibular disorders affect?
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 recurrent progressive 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
