1b// Vestibular System Flashcards
What is the role of vestibular organ?
capture low frequency motion (movements)
What is the role of the hearing organ?
capture high frequency motion (sound)
what are the cellular origins of the hearing and vestibular organs?
What are the inputs for a vestibular system?
movement and gravity
how are movement of gravity (inputs) for the vestibular system detected?
mechanical sensors
(canals and otoliths)
What happens to the input to mechanical sensors of the vestibular system?
the CNS integrates this info and generates responses
What are the outputs of the vestibular system?
the outputs are perception and reflexes that maintain posture and gaze
ocular reflex
postural control
Describe the whole process (input and output) of the vestibular system?
Label.
Where are the utricle and saccule located? And what are they joined by?
in the vestibule and are joined by a conduit
the saccule is also joined to the cochlea
How many semicircular canals are there on each ear?
3 each
ant, post and lateral
What do the semicircular canals have on their side? And what arte they filled with?
an ampulla on one side, and they are connected to the utricle
filled w/fuid and respond to movement
What are the otolith organs and where are they located?
Utricle and saccule are the otolith organs. Their cells are located on the maculae, placed horizontally in the utricle and vertically in the saccule
Label.
What do maculae contain? (3)
The maculae contain the hair cells, a gelatinous matrix and the otoliths on top. These otoliths are carbonate crystals that help the deflection of the hairs.
What is otolith movement?
linear acceleration and tilt
What type of movement does the utricule have?
horizontal movement
What type of movement does the saccule have?
vertical movement
Where are the hair cells in the canals located?
in the ampulla
Label.
What are the orientation of the canals in the head?
defines 3 planes
anterior
posterior
horizontal
anterior and post canals form a 90 degree angle
lateral canals are horizontal to the other canals
therefore they work in pairs
- 6 total canals both ears
What is the biggest cilium in vestibular hair cells called?
kinocilium
What do cilia allow? And what does head movement generate?
Cilia allows the cells to depolarise the cell with movement of the endolymph generated by head movement
towards the kinocilium= dfepolarisation
What type of potential do hair cells have? And what does that have?
Hair cells have a resting potential which has a basal discharge to the nerve
What happens when hairs move towards or away the kinocilium?
Hairs moving towards the kinocilium generates depolarization and an increase in nerve discharge.
Hairs moving away from the kinocilium generates hyperpolarization and a reduction in nerve discharge.
Where do primary afferents end?
in vestibular nuclei in the brainstem (pons)
Label.
What are the functions of the vestibular system?
to detect and inform about head movements
balance
to keep images fixed in the retina during head movements
What are the vestibular reflexes?
Vestibulo-ocular Reflex (VOR)
Vestibulo Spinal Reflex (VSR)
What is the vestibulo-occular reflex for?
Keeps images fixed in the retina
Describe the mechanism of the vestibulo-occular reflex?
Connection between vestibular nuclei and the oculomotor and (abducen) nuclei (CN3&6)
Eye movement in opposite direction to head movement, but same velocity and amplitude
How can you categorise vestibular disorders?
timing and laterality
acute AND unilateral
slow AND unilateral or any bilateral loss
What are the main complaints of acute and unilateral? and why?
imbalance, dizziness, vértigo and nausea
due to sudden asymmetry
What are the main complaints of slow and unilateral or bilateral loss?
imbalance and nausea – NO vertigo
What are the 2 types of location vestibular disorders?>
peripheral and central
Where are peripheral vestibular disorders located?
vestibular organ and/ or VIII nerve
What are examples of peripheral vestibular disorders?
Vestibular neuritis
Benign Paroxysmal Positional Vertigo (BPPV)
Meniere’s disease
Where are central vestibular disorders located?
CNS (brainstem/ cerebellum)
What are examples of central vestibular disorders?
Stroke
Multiple Sclerosis
Tumours
What is the clinical approach of a vestibular disorder? main diagnoses and core exam
*BPPV normal gelatinous matrix dislodges, so assymetrical signalling bc the crystals are moving
What are the red flags of vestibular disorders?
Headache
Gait problems
Hyper-acute onset (vascular event)
Hearing loss (e.g., blood supply to cochlea gone)
Prolonged symptoms (>4 days)
What are the balance disorders timing classification?
acute
recurrent
intermittent
progressive
What test do you do for acute balance disorders?
HINTS exam
What test do you do for intermittent balance disorders?
Dix-Hallpike test
What are examples of acute timing balance disorders?
Vestibular Neuritis
Stroke
What are examples of intermittent timing balance disorders?
Benign Paroxysmal Positional Vertigo (BPPV)
What are examples of recurrent timing balance disorders?
Migraine
(Meniere’s Disease)
What are examples of progressive timing balance disorders?
Schwannoma vestibular (VIIIth nerve)
Degenerative conditions (MS)
What does more dizziness most likely mean?
Benign Paroxysmal Positional Vertigo (BPPV)
What is significant about migranes?
any movement makes it worse
What is the HINTS exam?
What is nystagmus?
rhythmical, repetitive and involuntary movement of the eyes aka jerking movement of the eyes
What could support a diagnosis of Benign Paroxysmal Positional Vertigo (BPPV)?
The sudden and intermittent vertigo crisis which is very characteristic of this disorder.
Short lasting (minutes) spinning vertigo.
Triggered when getting up and lying down.
He does not refer to any symptoms when standing still
He does not mention any new hearing symptom accompanying the vestibular event, the hearing problems are clearly coming from previous time.
