Vestibular Function Flashcards
what is the function of the vestibular system?
controls posture and balance
where is the vestibular system found in the body?
inner ear
what are the name of the semi circular membraneous tubes?
labyrinths
what bone is the semi circular canals embedded into?
temporal bone
what fills the labyrinth tubes?
endolymph
state the importance of the structure of the semi circular canals
the canals are at 90 degrees to each other so tubes can detect movement in 3 dimensions
state the three structures which make up the vesicular system
- 3 semi circular canals
- utricle
- saccule
what is the swelling at the base of the semi circular canals called?
ampulla
what structure connects the three semi circular tubes together ?
the utricle
where are sensory hair cells found?
ampulla
utricle
saccule
what is the utricle and the saccule collectively known as ?
otolith organs
what structure in the vestibular system detects linear acceleration?
utricle
saccule
- otolith organs
what structure in the vestibular system detects rotational acceleration?
semi circular canals
what are the sensory receptors called which are present in the ampulla?
cristae
how many ampulla are there in the inner ear?
3
- one of each semi circular canal
what is the gelatinous structure which structure across the ampulla ?
cupula
how does the endolymph in the semi circular canals affect the ampulla?
when the endolymph moves in one direction the crista and cupula is pushed in the same way. This affects the cilia of the hair cells which directly synapse with the vestibular nerve.
state the two types of cilia of the hair cells
- kinocilium
- sterocilia
which of the two hair cell cilia are longer ?
kinocilium
state how rotational acceleration is detected when the head is rotated suddenly
- the ampulla moves with the bone
- endolymph stays stationary for a moment due to its own inertia
- the endolymph then produces drag and bends the cupula in the opposite direction
- as the endolymph catches up with the acceleration the cupula becomes unbent
- at a sudden stop, the bone stop moving so the ampulla is stationary but the endolymph still has its momentum so continues the path it had.
- this causes the cupula to be bent in the opposite direction
- this causes sense of movement and dizziness
distortion of cilia towards the kinocilium causes ?
- depolarisation
- hyper polarisation
depolarisation
- increase APs
distortion of cilia towards the stereocilia causes ?
- depolarisation
- hyper polarisation
hyper polarisation
- decrease APs
what is the function of the different cilia in the hair cells?
allows the brain to determine movement in time and space
where does most of the integration of sensory information take place?
cerebellum
what are the sensory apparatus in the utricle and saccule called?
maculae
is the macula in the utricle in a
- horizontal plane?
- vertical plane ?
horizontal
is the macula in the saccule in a
- horizontal plane?
- vertical plane ?
vertical
where do the cilia sit in the maculae ?
the cilia are in the gelatinous mass called the otolith membrane
whats embedded in the otolith membrane of the maculae ?
otoliths crystals
what nerve do the cilia on the hair cells synapse to?
vestibular nerve
do the otoliths have a lower or greater density to the endolymph?
greater density
when the head is tilted back what happens to the otoliths ?
the otoliths slide backwards towards the direction of the kinocilium causing depolarisation and increased APs
when the head is tilted forward what happens to the otoliths ?
the otoliths slide forwards towards the stereo cilia and causes hyper polarisation which decreases APs
what part of the vestibular system detects if the head is tilting forward?
the utricle
what part of the vestibular system detects if the head is lying down on its side?
the saccule
what is the function of the tonic labyrinthine reflexes?
keep the axis of the head in constant relationship with the rest of your body
when does the dynamic righting reflex occur?
when you trip
- to prevent you falling over
what species is very good at using their dynamic righting reflex?
cats
is there a strong association of vision with balance ?
yes
- visual system also sends powerful descending projections which control posture.
what is the static reflex of the eyes ?
When you tilt your head, the eyes intort/extort to compensate
what can be seen with Dynamic Vestibular Nystagmus ?
A series of saccadic eye movements that rotate the eye against the direction of rotation of the head
- quick flick back is away direction travelling
if the person is spinning towards the left, what way is the nystagmus ?
right nystagmus
what equipment can be used to research about nystagmus ?
Barany chair
what is caloric stimulation to research nystagmus ?
when either warm or cold water is poured into the persons ear. the temperature difference causes convention currents which affects the endolymph and causes nystagmus towards or away the affected side depending on the temperature of water poured in
what way does the nystagmus go if cold water is poured into the ear?
COWS
cold opposite
what way does the nystagmus go if warm water is poured into the ear?
COWS
warm same
lesions where abouts in the CNS can cause nystagmus ?
vestibular pathways
what is kinetosis ?
motion sickness
what are the symptoms of kinetosis ?
nausea vomiting decreases BP dizziness sweating pallor
what is vertigo?
perception of movement in the absence of movement.
what is Ménière’s disease?
Vertigo, nausea, nystagmus and tinnitus
what drugs can destroy the hair cells in the inner ear?
streptomycin
can vestibular impairment be compensated by the visual system?
yes
what are the symptoms of labyrinthitis ?
nausea vomiting decreases BP dizziness sweating pallor vertigo
