The Vestibular System Flashcards
Where is the vestibular system found?
Within the inner ear
Which bone in the skull are the labyrinths embedded ?
Temporal bone
The vestibular apparatus consists of what?
3 semi-circular canals
What are the vesticular apparatus connected to?
Utricle and Saccule
What are the swellings at the base of the semi-circular canals called and what is found there?
Ampulla
Cristae and hair cells
The utricle and saccule together are known as the _______
Otolith organs
What do the semi-circular canals detect?
Rotational acceleration
The utricle detects _______ and _______ movements
back and front tilt
The saccule detects _____ movement
Vertical
Where are the Cristae found ?
In the ampulla (At the swellings at the bottom of the semicircular canals)
What do the cristae consist of?
Cupula (Gelatinous substance which suspends the cillia
Cillia (Stereocillia & Kinocillium)
What are the cillia within the cristae directly linked to?
They synapse directly with the sensory neurons of the vestibulochoclear nerve
Endolymph does what to the gelatinous capula?
Pushes it activating receptor cells
What is the relationship with regards to movement of the cillia and the rotational movement of the head?
The cillia and cupula move in the opposite direction from one another at first until inertia is overcome
How does dizziness occur?
A sudden stop will caise the endolymph to continue to move due to momentum which creates a sensation of dizziness as the brain thinks you’re still moving
Distortion of the cillia in the direction of the __________ causes depolarisation and increases the discharge of AP’s in the vestibular nerve
Kinocillium
Distortion away from the _________ leads to hyperpolarisation and decreased discharge of APs in the vestibular nerve
Kinocillium
The sensory part of the Otolith organs are collectively known as what?
Maculae
What is the distribution of small and large cillia within the maculae?
One large cillia (Kinocilium) and many smaller cillia (Stereo cillia)
What is embedded in the otolith membrane in the maculae?
CaCO3 crystals known as otoliths
What is more affected by gravity endolymph or otolths ?
Otoliths, they have a greater density
What are the 3 vestibular reflexes?
Tonic labyrinthine reflexes
Dynamic righting reflexes
Vestibulo-ocular reflexes
What are the tonic labyrinthine reflexes ?
Keeps the head in line with the body - utilises neck proprioceptors
What are dynamic righting reflexes?
Quick postural adjustments that stop you falling when you trip (Profound in cats)
What are vestibulo-ocular reflexes?
Static reflex when you tilt your head and your eyes adjust to compensate
What is dynamic vestibular nystagmus?
A series of eye movements that rotate the eye in the direction of rotation so that gaze is preserved.
How can vestibular nystagmus be used to test vestibular function?
Post-rotatory nystagmus -Rotated in a chair
Caloric stimulation - Water temperatures can cause convection currents which affect endolymph. Warm water affects the same side and cold water affects the opposite side (COWS acronym)
What is Labyrinthitis?
Acute interference with vestibular function as a result of infection (Vertigo)
What is vertigo?
Perception of movement in the absence of movement
What is menieres disease?
Vertigo Nausea Nystagmus Tinnitus Associated with overproduction of endolymph which causes an increase in pressure
