Vestibular system Flashcards
What is the vestibular system?
- Senses equilibrium and balance
- Informs other systems about changes in orientation of the body
- Acceleration and deceleration of the head
Where are the sensory receptors located?
Within the labyrinth of the inner ear.
Via which nerve is sensory afferent information taken from the inner ear?
Vestibulocochlear nerve - CN VIII
What is the role of the endolymph fluid?
Found within the membranous labyrinth, it circulates between the spaces as you move and is constantly stimulating sensory organs in different planes to inform the brain where your head is
Where are the utricle and saccule found?
Macula - below the 3 semi-circular canals
What is the role of the hair cells?
They act as a sensor in vestibular organs as they are in contact with the dendrites of the vestibulocochlear nerve
What occurs when the hair cells bend?
There is a change in depolarisation/ hyperpolarisation so action potentials fire more frequently or less frequently
What do cristae detect?
Rotatory movement - dynamic balance
- occur during acceleration and deceleration
How do otoliths detect tilting of the head?
They are heavy, so tilting causes gravity to drag them, which bends the hair cells, causing a change in CN VIII input
Via which 3 nerves do the vestibular organs communicate to the extraocular muscles about orientation of our eyes and head?
III - occulomotor
IV - trochlear
VI - abducens
What are the 3 major postural reflexes the vestibular system is involved with?
- Vestibular reflex
- Tonic neck reflex
- Righting reflex
What does the vestibular reflex detect a change in?
The angle of the head relative to gravity
What does the tonic neck reflex detect a change in?
A change in the head:neck angle
How does the righting reflex work?
Uses vestibular and tonic neck reflex pathways together, plus skin pressure sensors.
- once head position is fixed relative to gravity, the body adjusts relative to the head
Which reflex fixes image on the retina during head rotations?
Vestibulo-ocular reflex
What causes motion sickness?
If there is a conflict between visual and vestibular input
Damage to which specific anatomical structures could present with signs of vestibular dysfunction?
- The inner ear – cristae, maculae
- Pons, medulla oblongata
- Thalamus
What clinical signs might you expect, in an animal with vestibular disease?
Lack of balance, falling to one side (in a circle), nystagmus (flicking of the eyes)
In which structure of the inner ear are the cristae ampullaris found?
Semicircular canals
Where in the CNS are the vestibular nuclei found?
Medulla oblongata and pons
