Vestibular Function Flashcards
What is the vestibular system?
Inner ear structure containing series of fluid filled membraneous tubes (labyrinths) which are embedded in the temporal bone
How many circular canal are there?
Three arranged at right angles to cover three dimensional space
Describe the structure of the semi-circular canal
Swelling at base (ampullae) containing sensory hairs
Inside are the receptors (cristae) which consist of gelatinous structure (cupola) which responds to the movement of endolymph
What structures detect rotational acceleration?
Hair cells
Sudden cessation of movement causes a series of dizziness/nausea, why?
Newfound intertia of endolymph
What two types of hair cells are there?
Kinocilium (single large hair)
Stereocilia (multiple small hairs)
Distortion in the direction of the kilocilium causes what nerve response
Increased frequency of vestibulocochlear nerve
How does the arrangement of the cupulae act in conjunction with the cerebellum to compose a three dimensional perception of the body
Cupulae all arranged differently
What comprises the otolith organs?
Utricle and saccule
What cavernous structure sits at the base of the ampullae of the semi-circular canals?
Maculae
What do maculae contain?
A set of cilia which protrudes into a gelatinous mass of otolith membrane
What can be said about the structure of the otolith membrane?
Contains otoliths (CaCO3) crystals
What is the function of otoliths?
Affected by gravity more than endolymph then detected which gives information about the position of the head
Other than position of the head, what other sensation do otoliths detect?
Linear sensation
Name the vestibular reflexes?
- Static reflex
- Post-retatory nystagmic reflex
- Caloric stimulation reflex
- Dynamic reflex
What is the static vestibular reflex?
Intorsion and extortion when the head tilts
Describe the dynamic reflex nystagmic reflex
Saccadic eye movements that rotates the eye (nystagmus) in the opposite direction of movement
What device is used to detect a dynamic vestibular reflex?
Barany chair
What is the pneumonic indicating the outcomes of the caloric stimulation reflex?
COWS
What is the danger of using too hot or cold water in the caloric stimulation test?
Reflex too strong, results in nausea/dizziness
What is vertigo?
Perceptual hallucination of movement in the absence of movement
What is Menieres Disease?
Overproduction of endolymph causing vertigo, tinnitus, nausea and nystagmus
What is the aetiology of Meniere’s Disease?
Unknown
What other factors can cause vestibular pathology?
Brainstem lesion
Chronic vestibular impairment
Drugs e.g. streptomycin
