Vestibular system Flashcards
what are the 3 main contributions to orientation?
- vision (visual space)
- Vestibular system (inertial space)
- Proprioception (internal space)
When there is no vestibular function and vision absence, what does this cause?
Tilting
What do the otholith organs and semicircular canals do?
Otholith - detect movements in any direction. Linear acceleration and tilt
Canals - angular velocity. the fluid in these provide the interia.
The otholiths and canals contain sensory hair cells called what?
Cilia
Movement of the body causes deflection of cilia hairs. movement of the hairs towards the what causes depolarisation and increases firing rate of afferent
Stereocilium
explain the push-pull action of left-right signals
2 vestibular systems (one in each ear) work together
Rotation and acceleration is signalled by the difference in firing rate between the 2 ears
Lose 2 ear and you’ll feel a very strong sense of rotation which causes vertigo and dizziness
What is the main role of the Utricle and Saccule (otholith organs) and what is their structure?
Postural stabilisation
utricle is approximately horizontal
saccule is approx vertical
They both respond to acceleration and gravity
Why is there tilt/acceleration ambiguity?
they can both do the same things to the hair. so without vision, one may feel like the other
Explain the somato-gravic illusion
produces a ‘false climb’ illsion in an aircraft. It is very dangerous for pilots as their intuitive response is to pitch the aircraft downwards causing it to crash. Pilots must therefore rely on instruments
What are the 3 semicircular canals and what do they do
anterior posterior and horizontal
they detect rotation in any direction
What happens to the capula in each semicircular canal if you spin for a long period of time?
it bend when the canal rotates. After a long period of time it’ll shift back into its neutral position and when you stop the fluid will move it in the opposite direction to give you post rotational effects.
After alcohol, the capula becomes lighter thanthan the surrounding fluid. Therefore rises when lying down, thus producing a left-bearing ___ when lying on your left ear. What is this known as?
Positional alcohol nystagmus
What is the vestibular ocular reflex?
Stabilisation of gaze is achieved via vestibular input from both sides of the head
What is caloric vestibular stimulation?
It is a method of modulating the firing rate of primary vestibular afferent, by irrigation of the ear canal with warm or cold water
how does caloric vestibular stimulation work?
- person lies down
- warm water irrigation into the ear
convection currents in horizontal canal to increase firing rates - which mimics head turn towards the irrigated ear - cold water irrigation
Convection currents reduce firing rates - which mimics head turn away from the irrigated ear
