Vestibular System Flashcards
What is the vestibular system responsible for?
Maintaining our balance, posture and spatial orientation.
What three receptor systems does the vestibular system integrate?
The eyes
General proprioceptive and cutaneous receptors
Vestibular receptors in the inner ear
What composes the inner ear?
The labyrinth, vestibular apparatus and cochlea
What two types of fluid are in the labyrinth? How do they differ in concentration of potassium and sodium?
Perilymph (low potassium, high sodium)
Endolymph (high potassium, low sodium)
What ducts does the vestibular part of the labyrinth have? What are the three other parts?
Semi-circular
Ampullae, utriculus and sacculus (the receptor cells are located here)
What cells in the ampulla detect movement? What is their purpose?
Hair cells (kinocilia) - they have kinetic sensitivity, they are sensitive to head rotation, and angular acceleration. They cause either depolarisation or hyper-polarisation depending on the direction of movement (away from the afferent nerve fibres for depolarisation).
What is the role of the endolymph in sensing head movement?
If the head moves one way, the endolymph moves in the opposite direction, which bends the cupula with it (the cupula contains the cilia and hair cells).
Where are the otoconia?
In the utriculus and sacculus
What are utricles?
Hair cells are polarized (excited) towards the striola (divides each macula into medial and lateral halves) HORIZONTAL ENCODING
What are saccules?
Hair cells are polarized away from the striola (divides each macula into anterior and posterior halves)
VERTICAL ENCODING
What do the hair cells of the utricles and saccules work together to do?
Provide a three dimensional representation of the direction of linear force. They sense the tilt of the head, as well as gravity.
What type of organs are saccule and utricle?
Otolithic
What is the vestibulo-ocular reflex?
Activation of the vestibular system causes eye movement in order to stabilize images on the retinas during head movement. This is done by producing eye movements in the direction opposite to head movement.
What is nystagmus?
Involuntary eye movements due to damage to vestibular apparatus, brainstem or cerebellum.
Cristae for ____ changes, maculae for ____ changes.
Rotational
Linear
VESTIBULO-OCULAR REFLEX - what is the pathway?
Vestibular nerve afferents –> central vestibular neuron –> extra-ocular motor neurons –> eye muscles
What vestibular nuclei are there? Where are they?
Superior, medial, lateral and inferior/descending - next to cerebellum/pons.
Where are the inputs from to the vestibular nuclei? Where do the outputs go?
From the vestibular apparatus and anterior lobe of cerebellum
To vestibulospinal tract and to eye muscle nuclei
What centre does the reticular formation have relevant to the eyes?
Gaze
The sense of equilibrium depends on signals coming from where? What does this record?
This must continuously be related to the positions and movements of the eyes and the body.
Vestibular apparatus - the position and movements of the head.
Signals from vestibular receptors contribute to our conscious awareness of…?
The position of the body in space
Name three peripheral vestibular pathologies.
Kinetosis (motion sickness)
Meniere’s disease
Benign paroxysmal positional vertigo (BPPV)
What causes BPPV?
This causes dizziness due to damaged (i.e. by head injury, infection, age) otoconia from the utricle being displaced.
How do you test for BPPV?
Hallpike manoeuvre (watch for nystagmus/if they get dizzy). Affected ear is pointed to the floor.
What are the symptoms of peripheral vestibular pathologies? (5)
Nystagmus Nausea Dizziness Disequilibrium Vertigo
What are the causes of peripheral vestibular pathologies? (5)
Nerve/inner ear infections Tumours Vascular insufficiency Trauma Endolymph imbalance
