1.6 The Vestibular System Flashcards
what is the vestibular system
a mechanosensory system that monitors linear and angular accelerations of the head and the body
- signals used for balance, posture and eye reflexes
what are the 2 primary functional systems
o The utricle and saccule (otolith organs) detect linear acc.
o The three semi-circular canals detect angular acc.
These five components are bony, hollow structures filled with endolymph.
what measures head tilt
hair cells in the utricle
what does the Relative motion between the otolithic membrane and hair cells results in
receptor activation
o Deflection of stereocilia in preferred direction of a hair cell results in its depolarisation and increase in afferent fibre spike rate.
o Deflection in opposite direction results in hyperpolarisation and decrease in spike rate
o Stimulation in orthogonal directions has little effect on spike rate
Modelled by a cosine-shaped function
how are hair cells arranged
in a way so different hair cells measure head tilt in different directions
uses an entire population of cells to encode a continuous parameter is a general principle used in the NS
what happens during head rotations
in the ampullae of the semicircular canals, the inertia of the fluid within the canals forces a deflection of the stereocilia of the hair cells
o The measuring axes of the cannels build an almost orthogonal system.
what refines the info about angular rotations
The signals of the horizontal canals as well as the signals of anterior/posterior canals may be combined to refine
what happens to avoid motion blur
the lateral eye muscles contract the counter-rotate the eyes
what is important in stabilisation reflexes
Such alignment of sensor and actuator axes can be of tremendous help when response speed is important
