vestibular system Flashcards
What is the vestibular system ?
Located in the ear
Important for reflex movement
Balance
Head position, self motion and spatial orientation
What is the vestibular system joined to?
The cochlea
Same fluids and ionic profiles
Movement can take place in 3 different axis. What are they ?
Roll: rotation around X axis
Pitch: rotation around Y axis
Yaw: rotation around Z axis
What are the two types of movement ?
Translational- static head tilts, detected by otolith (inner ear)
Rotational- detected by semi-circular canals
Where are vestibular hairs located ?
In the utricle, saccule (otolith organs), amplullae of the semicircular canals
Describe the spontaneous activity of the vestibular hair cells (experiment)
Reading from vestibular axon of utricle
Before and after head tilts there electrical activity in axon
Absence of stim = ion channels in stereocilia open
TONIC release of NT
What does the change in spontaneous vestibular nerve cell activity correlate to ?
The electrical acitivy of the hair cells and movement of the head
What are the otolith organs ?
Utricle and saccule
What is the sensor epithelium called ?
Macula
What is the otolithic membrane ?
Gel layer with calcium carbonate crystals
What happens to the macula when the head is tilted back?
Static tilt = gravitational force along the macula distorting hair cell processes
Describe the effect of linear head accelerations
Stereocilia bundles orientated towards the striola
Striola acts as axis of symmetry, hair bundles on either side have opposing morphological polarisation = differential pattern of excitability encoding head position
The utricle detects movements in what plane ?
Horizontal
The saccule detects movements in what plane ?
Vertical
What does the utricle and saccule both detect?
front-back translational movement and front-back head tilts
