Vestibular Function Flashcards
what is the vestibular system
Sensory system in control of posture and balance
Where is the vestibular system found
The inner ear. Series of fluid-filled membranous tubes (labyrinths) embedded in the temporal bone
What does the vestibular apparatus consist of
3 semi-circular canals, ampulla, utricle (semi-lunar canals connect to this), saccule
Where are the sensory hairs found
Ampulla
(Utricle and saccule have similar sensory hairs)
What movement does the utricle detect
Back/front tile and horizontal acceleration (e.g. in the car)
What movement does the saccule detect
Vertical acceleration (e.g. in lift)
What movement does the semi-lunar canal detect
Rotational acceleration (e.g. spinning)
What are the hair cells embedded into
Cupula (stretches width of the ampulla)
What fluid circulates the semi-lunar canals
Endolymph
How does movement of endolymph fluid sent signal back to the brain that you are moving
Movement of Endolymph fluid distorts the cupula - by distorting the cupula the hair cells are distorted which sets up action potential in the vestibular nerve sent back to the brain
What is the maculae
Combination of the utricle and saccule
What are otoliths
CaCO3 crystals which detect the tilting of the head
What is the tonic labyrinthine reflex
Keeps the axis of the head in constant relationship with rest of the body
Uses information from maculae and neck proprioceptors
What is the dynamic righting reflex
Rapid postural adjustments that are made to stop you falling when you trip.
Long reflexes involving extension of all limbs (profound in cats)
Vestibulo-ocular reflexes
Association between vestibular apparatus, visual apparatus and postural control
Eyes are able to compensate to some extent for a loss of input from vestibular system
What is vestibular nystagmus
Movements which rotate the eye against the direction of the head and body so that the original direction of gaze is preserved despite head rotation (think about when going round slow roundabout)
Extent of eye movement restricted by eye movement, when eyeball reaches end of range of motion it rapidly flicks back to starting position (i.e. straight ahead)
R rotation —> R nystagmus
(Often get nystagmus when drunk)
How can nystagmus be used to test vestibular function
Outer ear washed with cold or warm fluid, temperature difference from core 37 Celsius sets up convection currents affecting endolymph. Cold causes nystagmus away from affected side, warm towards affect side
COWS - Cold Opposite, Warm Same
Cold into R ear —> L Nystagmus, Warm into R ear —> R Nystagmus
What causes motion sickness
Visual and vestibular system inputs to cerebellum in conflict (e.g. vestibular system indicates rotation but visual doesn’t)
Cerebellum generates sickness signal to hypothalamus
What symptoms are caused by “sickness signal” from cerebellum to hypothalamus in motion sickness (6)
Autonomic neuropathy symptoms (ANS):
nausea, vomiting, decreased BP, dizziness, sweating and pallor
What causes labyrinthitis, what are the symptoms
Acute interference with normal vestibular function as a result of infection
ANS symptoms and vertigo
What is vertigo
Perception (hallucination) of movement in the absence of movement (may also be nystagmus, impairment of posture and balance)
What causes symptoms Ménière’s disease
Over production of endolymph (unknown why) causing increased pressure
What are the symptoms of Ménière’s disease (what is the distinguishing feature from labyrinthitis)
Vertigo, nausea nystagmus AND tinnitus (distinguishing feature from labyrinthitis)
