The Vestibular System Flashcards
what is the point of the vestibular system?
it tells us which way is up and where we are going.
what does the vestibular system contribute to?
keeping our eyes still as we move,
maintaining upright posture,
and our ability to perceive our own movement within space.
what is the gross anatomy of the vestibular system?
the semi-circular canals,
an enlargement at the end of the canals called Ampulla,
and the otolith organs.
what are the structures in the vestibular system that relate to head rotation?
the semi-circular canals.
what are the structures in the vestibular system that relate to head tilt and linear motion?
the otolith organs.
what are the 3 semi-circular canals (scc) ?
the anterior vertical scc,
the posterior vertical scc,
the horizontal vertical scc.
what are the 2 otolith organs?
the Utricle,
the Saccule.
where are the hair cells located?
in the Ampulla and in the Saccule/Utricle.
what happens when the hair cells are at rest?
the bundles are upright and not being stimulated in a direction.
what happens when the hair cells are being stimulated? (towards taller stereocilia)
fluid moves hair bundles towards the taller stereocilia,
results in depolarisation,
and increased in frequency of nerve impulses.
what happens when the hair cells are being stimulated? (towards shorter stereocilia)
fluid moves hair bundles towards the shorter stereocilia,
results in hyperpolarisation,
and decreased impulse frequency.
how are hair cells in the vestibular system structurally different to the auditory hair cells.
they are more clumped together because they aren’t as sensitive to movement,
they also have a kinocilium which are kept through the cell’s life.
in the vestibular system there are 2 types of hair cells:
Type 1 – have a calyx on the afferent dendrite that surrounds the hair cells.
Type 2 – across from presynaptic area is an afferent neuron.
what is the specific sensory patch where the hair cells are found?
the Macula.
the Macula has a striola which divides the structure into 2:
divides it into part dependant on how the hair cells are orientated.
what kind of membrane is above the hair cells?
an otolithic membrane that has a otoconia on it.
gravity can influence the otoconia and therefore…
can move the otolithic membrane.
when the otolithic membrane moves it…
causes displacement of the hair bundles.
what structures are in the Ampulla?
there are ampullary crista.
what is in the ampullary crista?
the cell bodies of the vestibular hair cells and the afferent fibres are embedded.
what is the Ampulla filled with?
endolymph.
what does this mean:
the polarity of the hair cells in the ampulla is the same?
all the hair cells are orientated in the same direction.
explain:
the semi-circular canals detect angular acceleration?
when head is rotated / angular,
the endolymph in the ampulla moves slightly in the opposite direction,
pushing the cupula,
deflecting the hair bundles,
causing depolarisation or hyperpolarisation.
what is the vestibular ocular reflex? (basic)
we are able to read whilst shaking our heads, but can’t read whilst shaking the paper.
what allows us to move our extraocular muscles in an opposite to that of the head’s movement.
info link between the vestibular nuclei, the oculomotor nucleus, and the abducens nucleus.
what is vestibular nystagmus?
allows the resettling of eye position during sustained to head movement.
