Vestibular Function Flashcards
What is the function of the vestibular system?
Control of posture and balance
Where is the vestibular system found?
In the inner ear
In which bone are the labyrinths embedded?
Temporal bone
Which structures make up the vestibular apparatus?
3 semi-circular canals, utricle and saccule
What are the swellings at the bottom of the semi-circular canals called?
Ampulla
What are the utricle and saccule collectively known as?
Otolith organs
What is the function of the otolith organs?
They detect linear acceleration and the position of the head in space. Back/front tilt is detected by the utricle. Vertical movement is detected by the saccule
Which structure in the inner ear detects rotational movement?
Semi-circular canals
Which receptors are contained within the ampulla and what do they consist of?
Cristae - made up of cupula (a flexible gelatinous structure)
What is embedded in the cupula?
Cilia of hair cells that synapse directly with the sensory neurons of the vestibular nerve (CrN VIII)
How do the hair cells in the cupula detect rotational movement?
If the skull is rotated left or right from rest the endolymph does not move at first but the ampulla does because it is embedded in the skull. This produces a drag which bends the cupula and cilia in the opposite direction to movement
What are the two types of cilia of the hair cells?
One large kinocilium and progressively smaller stereocilia
What happens to AP discharge when the distortion of the cilia is in the direction of the kinocilium?
It is increased
What happens to AP discharge when the distortion of the cilia is away from the kinocilium?
It is decreased due to the hyperpolarization
Where does the integration of the sensory information from the cupula take place?
Cerebellum
What are the sensory receptors of the otolith organs called?
Maculae
What are otoliths and where are they found?
CaCO3 crystals found in the otolith membrane
What happens to the otoliths when the head is tilted?
They move and so does the otolith membrane. This moves the cilia
What is kinaesthesia?
Perception of movement and body perception
What is the function of the tonic labyrinthine reflex?
It keeps the axis of the head in a constant relationship with the rest of the body
What is the function of the dynamic righting reflex?
It produced rapid postural adjustments that are made to stop you falling when you trip (involves extension of all limbs) and is most profound in cats
What happens to people who have destruction of the vestibular apparatus when they close their eyes?
They immediately lose balance
What is kinetosis and what is it caused by?
Motion Sickness - caused by powerful maintained stimulation of the vestibular system
What is the presentation of kinetosis?
Nausea, vomiting, decreased BP, dizziness, sweating and pallor (all ANS symptoms)
