vestibular function Flashcards
what do vestibular labryinths sense?
head motion
how many axes of rotation are detected by the semicircular canal?
one of the three
what does the otolith ( utricle and saccule detect)?
3 axes of translational movement and force of gravity
what is the purpose of the vestibulo-ocular -reflex?
to keep the visual scene steady on the retina during head movements
what structure is the ampulla apart of and what are some of it’s properties?
it is apart of the semicircular canal of the inner ear and it has hair cells w/ directional orientation
what is the semicircular canal important for?
angular acceleration in ( rotational direction)
what is the utrical and saccular detection system used for?
inertial guidance detectors and detectors of gravity
what do the sacculus and the utricle striola separate?
hair cells with opposite polarity
how is the saccculus directed
VERTICALLY
how is the utricle directed?
horizontally
the ________ of a group of hair cells located on the same side and are in the same orientation
kinocilia
the ampulla of each canal are oriented in _________?
the same direction
why is there continuous representation of all body movements?
because there are structures on both sides of the head
in the utricle and the sacculus the cilia of the hair project into the _________ _________ _________
gelatinous otolithic membrane
the mecahnism for stimulating hair cells differs btw __________ vs ___________ and ___________
ampulla vs. the utricle and the sacculus
what is the otoconia?
a calcium carbonate covering which provides mass to cover the membrane
*when you are accelerating forward what is the displacement of the otolithic membrane and hair cells? and what type of polarization is this?prob on test see pg 914
backward
depolarization( i.e. increasing response of innervating CN8 -excitation)
*when you are decelerating what is the displacement of the otolithic membrane and hair cells? and what type of polarization is this? prob on test see pg 914
forward
hyperpolarization (i.e. decreasing response of innervating CN8 -inhibition)
forces acting on the head and the displacement of the otolithic membrane will __________ or ___________ sets of hair cells
excite or inhibit
* the displacement of the otolithic membrane and hair cells is in the _________ direction of the _______force prob on test
the opposite direction of the inertial force
how many degree of rotation do we detect?
three ( i.e. 3 axis: yaw ( z axis), roll (x axis), pitch( y axis) see p6 916
which canals on either of the head work together?
the anterior canal on one side works with the posterior canal of the other side
explain the mechanism of how the anterior canal on one side works with the posterior canal of the other side
rotation in a particular direction will yield excitation of the hair cells in one canal of a pair and inhibition in the other
the semicircular canal is filled with?
fluid
what membrane is displaced by the inertia of the fluid in the canals?
the cupula
fluid flow and angular acceleration are in the _______ direction
opposite
when you move your head to the right what happens to the vestibular nerve on the right and what happens to the one on the left
the one on the right is excited ( depolarized) and the one on the left is inhibited ( hyperpolarized)
explain the vestibular ocular reflex with and example of turning to the left
the left vestibular nuclei is excited while the left is inhibited–> the left vestibular nuclei excites the right abducens and via the mlf the left CN III is excited and the eyes turn right , the inhibition o of the left vestibular nuclei inhibits the left abducens and right CN III
why does nystagmus result in pathological conditions
the brain can mistake the resting discharge as representing a head movement
e.g. if there is no firing from the left canal and there is baseline firing in the right canal there will be a right nystagmus ( named for the resetting of the saccade) because it mimicks rotation to the right i.e. a slow movement of eyes to the left ( as in a normal rotation to the right) and a snap back to the right quickly
if a person has no firing in the right ear which way would they fal if they try to get up from their seat and why ?
they would fall the right
the pathology mimicks a rotation to left so the person thinks they are falling left and they will excite their extensor muscles to compensate and maintain posture which disrupts balance
