vestibular system Flashcards
where is vestibular system
It is encased in the bony labyrinth and is continuous with the cochlea
what are functions of vestibular system
Providing spatial reference for other sensory motor co-ordinations
Providing compensatory reflexes (Vestibular Ocular reflex)
Tuning cardiovascular function for re-orientations
Helping with perception of motion in space
Controlling balance reactions
what is the vestibular system
sensory organ for detecting sensations of equilibrium
name the otolith organs and their functions
Utricle and Saccule
Each has a sensory area called a MACULA
Detects LINEAR ACCELERATION and POSITION OF THE HEAD DUE TO GRAVITY
name the semicircular canals and their functions
Anterior, Posterior, Lateral
Canals are filled with ENDOLYMPH
Have swelling at the end called AMPULLA
Detects ANGULAR ACCELERATION
what do the maculas contain
hair cells which synapse with the vestibular nerve
describe the structure of these hair cells
hair cells have minute projections called STEREOCILIA and one longer projection (on one side) called a KINOCILIUM
what is the gel layer that the stereocilia and kinocilium project project into
OTOCONIA (gel containing small calcium carbonate crystals )
describe how linear acceleration and gravity is detected by the otolith organs
Gravity pulls on crystals called OTOCONIA or linear acceleration causes them to move
The otoconia in turn cause the stereocilia and kinocilium to move
This opens ion channels and causes depolarization or hyperpolarization of the hair cells
Thus, signals are sent via the vestibular nerve to give an idea of linear acceleration and the position of the head due to gravity
how are the three semi-circular canals arranged
at right angles to each other
describe the structure of semi circular canals
They each have an enlargement at one end which is called the ‘ampulla’
They are also filled with a fluid called endolymph
describe how the SCC aid in detecting angular acceleration
When you move your head one way, your SCC also move that way, however, the endolymph moves in the OPPOSITE DIRECTION
This moves a structure in the ampulla called the CUPULA and stimulates hair cells and vestibular nerves
The semi-circular canals give us information about angular acceleration
describe what happens in the sac when the head is moved to the left
At least one of semi-circular canals ON BOTH SIDES OF YOUR HEAD will move to the left
Endolymph in the SCC will move to the right (clockwise)
On the left hand side the endolymph will be moving in such a way that it STIMULATES the hair cells and there is increased firing
On the right hand side the endolymph will be moving in such a way that it INHIBITS hair cells and decreases firing
Thus when you move your head to one side, there is increased firing of nerves on the opposite side
define dizziness
a term used to describe a range of sensations, such as feeling faint, woozy, weak or unsteady
define vertigo
a feeling of spinning or whirling when you are not actually moving
