Vestibular System Flashcards
What does the vestibular system control?
Posture and balance
Where is the vestibular system found?
Inner ear (labyrinths embedded in temporal bone)
What does the vestibular apparatus consist of?
3 semicircular canals
Utricle
Saccule
What are the utricle and saccule collectively known as?
Otolith organs
What do the otolith organs detect?
Linear acceleration
Encode info about position of head
What is the function of the utricle?
Back/front head tilting
What is the function of the saccule?
Vertical movement
What do the semicircular canals detect?
Rotational acceleration
Where are the sensory cells located in the semicircular canals?
Ampulla (base of ssc)
What are cristae?
Sensory receptors consisting of capula which stretch across ampulla and respond to movement of endolymph fluid
What are found in the capula?
Cilia of hair cells which directly synapse with sensory neurons of vestibular nerve
What do the hair cells in the scapula detect?
Rotational acceleration
How do the hair cells respond to rotational acceleration?
Endolymph inertia produces drag, bends the capula and cilia in opposite direction to movement
Sudden stop- endolymph still moves, sense of movement and dizziness
What are the 2 types of cilia?
Kinocilium
Stereocilia
What is the effect of cilia distortion in direction of kinocilium?
Depolarisation and increased APs in vestibular nerve
What is the effect of cilia distortion in direction away from kinocilium?
Hyperpolarisation and decreased discharge of APs in vestibular nerve
What is the sensory apparatus of the utricle and saccule known as?
Maculae
How are the maculae different within the otolith organs?
Utricle - orientated on horizontal plane
Saccule - orientated on vertical plane
What is the tonic labyrinthine reflex?
Keeps head axis in constant relationship with rest of body
What is the dynamic righting reflex?
Rapid postural adjustments that are made to stop you falling when you trip
What is vertigo?
Perception of movement in the absence of movement
What symptoms are associated with Meniere’s disease?
Vertigo
Nausea
Nystagmus
Tinnitus
What are the CaCO3 crystals found in the otolith membrane called?
Otoliths
What detects head tilting?
Macula in utricle
What does head tilting cause?
Otoliths and otolith membrane move, distorts jelly and moves cilia
What is static reflex?
Eyes intort/extort to compensate for head tilting so image stays the right way up
What is dynamic vestibular nystagmus?
Eye movements that rotate the eye against direction of rotation of head and body so that direction of gaze is preserved
How is vestibular function tested?
Post rotatory nystagmus
Caloric stimulation
