Vestibular system Flashcards
(81 cards)
What is important to remember about balance
Everything is related to balance- ear (series of impulses ) and central processing.
What are the inputs to the vestibular system
Visual system Inner ear ( detecting rotation, movement and gravity) Pressure- detected by joints and limbs
What are the outputs of the vestibular system
These inputs feed into the CNS (brainstem, cortex and cerebellum)
We have reflex responses- the vestibular-ocular reflex
And also postural control ( spinal reflex)
Nausea is another potential output- if mismatch between auditory and visual perceptions
What happens if these reflexes are not quick
You would lose balance and fall over
Summarise what is meant by the vestibular system
The vestibular system is the only sensory organ specialised to transduce absolute motion in space. Angular (rotatory) motion (of the head) is sensed by the semicircular canals; acceleration
of the head and strength and direction of gravity are sensed by the otolith organs.
What does CN8 nerve conduct
Both vestibular and auditory informaiton
What is the inner ear known as
The labyrinth
Where is the inner ear located
In the petrous part of the temporal bone
This the hardest part of the temporal bone (and the body in fact)
So the inner ear is well protected
Otherwise, you would lose balance and hearing- upon trauma
The inner ear and its structures are carved within the bone- so it fits perfectly
How many parts of the vestibular organ are there
5
Or you could say there are 5 vestibular organs
What are the two otolith organs
Saccule
Utricle
Saccule is closer to and connected to the cochlea
The utricle is connected to the saccule
Describe the semi-circular canals
3 semi-circular canals (anterior, posterior and lateral)
All connected to the utricle
Everything is connected in the inner ear
Where is the perilymph found
Between the vestibular structures and the bone
Were is the endolymph found
Within the vestibular organs themselves
What do the semi-circular canals have at the end which attaches them to the utricle
An ampulla
Anterior and posterior semi-circular canals join at their non-ampulla ends
Lateral canals do not join to any other semi-circular canal
What is the function of the endolymph fluid
Help move hair cells for transduction (for sound or movement)
Why is the orientation of the vestibular organ important for its function, but not so much for the cochlea
Because the stimulus for the vestibular organ is movement- so it matters what plan and orientation you are moving in
Where abouts in the labyrinth are the vestibular organ and cochlear found
Cohclea- anterior labyrinth
Vestibular organ- posterior labyrinth
Describe the orientation of the semi-circular canals
Anterior canal: 45deg anterior
Posterior canal: 45deg posterior
Lateral canal: lie horizontally
What structures are found within the semi-circular canals and within the otolith organs
Hair cells (same as the cochlear- but not called inner or outer)
Summarise the hair cells of the vestibular organ
Type I: More in number Direct afferent, indirect efferent Round shaped Like the inner hair cells of the cochlea Type II: Direct afferents and efferents More efferents Like the outer hair cells of the cochlea
What is important to remember about the hair cells of the vestibular organ
No special distribution of hair cells- as in the cochlea
As in the cochlea, tight junctions seal the apical surfaces of the vestibular hair cells, ensuring the endolymph selectively bathes the hair cell bundle while remaining separate from the perilymph surrounding the basal portion of the hair cell
Where are the hair cells found in the vestibular organ
The two otolith organs
The ampullae
Describe the two parts of the labyrinth (the vestibular organ)
The membranous sacs within the bone are filled with fluid (endolymph) and are collectively called the membranous labyrinth.
Between the bony walls (osseous labyrinth) is another fluid, the perilymph, which is similar in composition to the CSF.
Summarise the otolith organs (i.e the static labyrinth)
§ There are 2 otolith organs:
o Utricle – senses movement in the horizontal plane.
o Saccule – senses movement in the vertical plane.
§ The otoconia is a layer of calcium carbonate on top of a gelatinous layer and as it is heavy, movements of the head displace the otoconia and thus pull the hair cells.
o Linear acceleration will also move the heavy otoconia layer.