Vestibular System Flashcards
What is the vestibular system?
Sensory system essential in control of posture and balance
Where is the vestibular system found?
Inner ear
What composes the vestibular system?
Series of membranous fluid-filled tubes, embedded in the temporal bone
What detects change in movement in the vestibular apparatus?
Hair cells
What does the vestibular apparatus consist of?
Three semi circular canals
Utricle
Saccule
What contains the sensory hair cells?
Ampulla
What are the otolith organs?
Utricle and saccule
What is the function of the otolith organs?
Detect liner acceleration and encode information about position of the head in space
What positions of the head do the otolith organs detect? (specific)
Utricle - front and back tilt
Saccule - vertical movement
What do the semi-circular canals detect?
Rotational acceleration
What do the cristae consist of?
Flexible gelatinous structures called cupula
What is the function of the cupula?
Responds to movement of the endolymph fluid within the canals
What are the cristae?
Sensory receptors in the ampulla of semi circular canals
What do the cristae synapse with?
Sensory neurons of the vestibular nerve
Why, if the skull is rotated, does the endolymph not move at first?
Inertia
What does the inertia of the endolymph cause?
Produces drag which bens the cupula and consequently the cilia in the opposite direction to the movement
What are the two types of cilla of the hair cells?
Kinocillum and sterocilia
What does distortion of the cilia in direction of the kinocilium cause?
Depolarisation and increased discharge of APs in the vestibular nerve
What does distortion of the cilia away from the kinocilium lead to?
Hyperpolarisation and decreased discharge of APs in the vestibular nerve
What does the change in discharge of APs dependent on direction of movement allow for?
Brain to determine movement in time and space
Where does most of the integration of the sensory information from the vestibular system take place?
Cerebellum
What are the sensory apparatus of the saccule and utricle collectively known as?
Maculae
How are the macula orientated in the saccule and utricle?
Horizontal plane in the utricle
Vertical pain in the saccule
What are otoliths?
Calcium carbonate crystals embedded in the otolith membrane
What do the vestibular nuclei project to?
Ipsilaterally, bilaterally and contra laterally to descending motor pathways
Via thalamus to cerebral cortex - perception of movement and body movement
What do the vestibular nuclei receive input from?
Proprioceptors signalling limb and body position - also neck and eye muscles
What tracts do the vestibular system reflexes involve?
Vestibulocortical and vestibulospinal tracts
What are the tonic labyrinth reflexes?
Keep the axis of the head in a constant relationship with the rest of the body.
Uses information from maculae and neck proprioceptors
What are the dynamic righting reflexes?
Rapid postural adjustments that are made to stop you falling when you trip
What is dynamic vestibular nystagmus?
Series of saccadic eye movements that rotate the eye against the direction of rotation of head and body so that original direction of gaze is preserved
Exent of eye movement restricted when eyeball comes to end of its range off movement
What do afferents from the semi-circular canals project and connect to?
Afferent fibres travelling to the extraocular muscles and thus have strong input to influencing eye movement
What does an acute interference with normal vestibular function as a result of infection result in?
All ANS symptoms and vertigo
What is vertigo?
Perception of movement in the absence of movement
What are the symptoms of Meniere’s disease?
Vertigo
Nausea
Nystagmus
Tinnitus
What is Meniere’s disease?
Associated with subjective noise, associated with over production of endolymph causing increased pressure
What drug can affect the inner ear?
Streptomycin
What can lesions of the brain stem cause? (in relation to vestibular system)
Nystagmus
