The vestibular system Flashcards
What are the 3 semi-circle canals?
Anterior vertical
Posterior vertical
Horizontal
Where are hair cells located?
In the ampulla
What structure aids with linear movement?
Otolith
In which direction does the utricle aid movement with ?
Left
Right
Backwards
Forwards
In which direction does the saccule aid movement with?
Up
Down
Where are hair cells located?
In the ampulla
Why does endolymph have a high potassium conc?
Potential difference provides an electrochemical gradient
- Depolarisation of the hair cells
How does depolarisation occur in hair cells?
Due to opening of tip links
- Occurs when taller stereocilia cells pull on tip links
- Opens non-selective cation channels and allow cations to move in
- Causes depolarisation
How does hyperpolarisation occur in hair cells?
Tip links push on shorter stereocilia
- Tension on tip links relaxes and channels close
- Leads to hyperpolarisation, more negative membrane potential
How are vestibular hair bundles different to auditory hair cells?
The vestibular saccular hair cells keep their kinocilium throughout their life
- Higher resistance due to less flexibility
How do type 1 and type 2 vestibular hair cells differ?
Type 1 have a single afference surrounding the base of the vestibular cell
Whereas
Type 2 have vesicles that are released onto afferent dendrites
What is the striola?
A line on the utricle which set the polarity of the hair cells
- Hair bundles are arranged in different ways and cause opposite inhibitory and excitatory effects
What lies on top of the gelatinous otolithic membrane?
The otoconia calcium carbonate crystals
How does the GOM move?
The otoconia calcium carbonate is moved by gravity and causes movement on the GOM
- The hair bundles are pushed and pulled with the GOM
How does endolymph protect the vestibular system?
The endolymph moves more slowly than physical structures so buffers the movement
How is angular acceleration detected?
The endolymph displaces the cupula
- This orientates the hair cells
How do semi-circular canals work in pairs?
An anterior and posterior canal lie in parallel with each other
- One is activated and the other is inhibited
- Functional pair
Where is the vestibular nuclei found?
In the medulla
Why does the vestibular nuclei interacts with the cerebellum?
Important for balance
- Feeds into spinal cord and cerebral cortex
What does interactions between the vestibular nuclei and the reticular formation cause?
Visceral response
-> Ocular motor nuclei inputs into the muscles that control your eyes, aids eye muscle correction
Why are you able to move your head and still read?
The vestibular system is faster than the ocular system
If endolymph moves to the right, which horizontal canal is activated?
The left horizontal canal
What enables the resetting of eye position during a sustained head rotation?
Vestibular nystagmus
What is the slow phase of sustained head rotation?
Eyes rotate in the opposite direction to head movement
What is the quick phase of sustained head rotation?
Rapid resetting movement back to the centre of the gaze
