Vestibular system Flashcards
What are the three main inputs of the vestibular system?
Proprioceptive
Vestibular information
Visual
What are the two main outputs of the vestibular system?
Ocular reflex
Postural control
Where is the vestibular organ located?
Within the posterior area of the inner ear
which cells are located within the vestibular organ?
Hair cells
What two structures are joined by a conduit in the vestibule?
The utricle and saccule
What is the utricle?
The utricle detects linear accelerations and head-tilts in the horizontal plane.
What are the three semi-circular canals?
Anterior
Posterior
Lateral
Which structure connects the semi-circular canals with the utricle?
Ampulla
Which bone is the vestibular organs located in?
Petrous part of the temporal pone.
What term refers to the biggest cilium on vestibule hair cells?
Kinocillium
What is the function of stereocilia on vestibular hair cells?
Cilia allows the cells to depolarise the cell with movement of the endolymph generated by head movement. Cilia are orientated to a particular side, deflection will induce cellular depolarisation in response to endolymph movement
What are otoliths?
The otoliths (statoconia) are small calcium carbonate crystals which put pressure on the cilia, inclining them, thereby stimulating the sensory hair cells.
Where are the utricle and saccule cells located?
In the maculae
How are utricle cells organised?
Horizontally
Which otolith organ cells are organised vertically?
Saccule
What is the maculae?
Contains the hair cells, a gelatinous matrix and the otoliths.
Where are the hair cells located within the semi-circular canals?
In the ampulla, the rest of the canal contains endolymph
What fluid comprises the semi-circular canals?
Endolymph (High in potassium ions)
Which structure within the ampulla contains hair cells?
The crista
Which structure surrounds the crista ampularis?
The cupula
What function is performed by the cupula?
Helps hair cell movement, facilitated by endolymph movement
What angle is formed between the anterior and posterior canals?
90 degrees
Where are the vestibular nuclei located?
Rostral medulla
Which nuclei is receives primary afferents?
Vestibular nuclei
What four projections arise from the vestibular nuclei?
1) Spinal cord
2) Nuclei of the extraocular muscles
3) Cerebellum
4) Centres for cardiovascular and respiratory control
Which vestibular nuclei are concerned with vestibulospinal reflexes?
Lateral, medial and inferior nuclei
How many vestibular nuclei are there?
Superior, lateral, medial and inferior
Which vestibular nuclei are concerned with the vestibulocerebellar reflex?
Inferior
Which vestibular nuclei are concerned with the vestibulo-ocular reflex?
The inferior nuclei
Where is the main vestibular cortex located?
In the parietal lobe (Parieto-insular vestibular cortex)
What are the three main vestibular system functions?
To detect and inform about head movements
Postural control
To keep imaged fixed in the retina during head movements
What are the three vestibular hair cell potentials?
Resting
Excitation
Inhibition
What is the relationship between neural firing rate in the right and left ear?
There is an antagonistic relationship (Inhibition v excitation)
Which otolith organ is concerned with horizontal linear acceleration?
Utricule
Which otolith organ is concerned with vertical movement?
Saccule
How is angular acceleration inputted?
The endolymph within the semi-circular canals exerts pressure onto the cupula, inducing hair cell displacement, subsequent information is transmitted to the brainstem and integrated within.
The output signal is via the vestibulocohclear nerve (velocity)
What are the semi-circular canal pairs?
Both laterals
Left anterior with right posterior
Left posterior with right anterior.
What are the two main vestibular reflexes?
The vestibulo-occular reflex
The vestibulo spinal reflex
What is the vestibulo-occular reflex?
The vestibulo-ocular reflex (VOR) is a reflex acting to stabilize gaze during head movement
Which nuclei are connected within the VOR?
The vestibular and oculomotor nuclei.
How are eye movements coordinated in the VOR?
Eye movements in the opposite direction to head movement, with same velocity and amplitude.
What is the VSR?
Postural control, avoidance of falls and compensatory body movement according to hed movement
Motor neurones to limb muscles (lateral tract)
Motor neurones to neck and back muscles (medial tract)
What is the initial assessment of the vestibular system?
Anamnesis
What is Anamnesis?
A patient’s account of their medical history
What are the four main clinical vestibular assessments?
Caloric test
Video head impulse test (vHIT)
Vestibular evoked myogenic potential (VEMP)
Rotational test
What is the main balance disorder?
Vertigo
How is vertigo categorised?
Based on location of the affected structure and evolution of signs and symptoms
What is vertigo?
Vertigo is the sensation that the environment is spinning around relative to oneself.
What are the main peripheral vestibular disorders concerned with the larbyrinth or VIII nerve?
Vestibular neuritis
Benign positional vertigo (BPPV)
Meniere’s disease
Unilateral and bilateral vestibular hypofunction
What is BPPV?
Benign paroxysmal positional vertigo (BPPV) is a peripheral vestibular disorder that manifests as sudden, short-lived episodes of vertigo elicited by specific head movements.
Which semi-circular canal is typically associated with the migration of otoliths in the endolymph?
Posterior semi-circular canal
What is a vestibular schwannoma?
A benign cerebellopontine angle tumour that grows from the superior vestibular component of the vestibulocochlear nerve, usually presenting with unilateral sensorineural hearing loss.
What is the evolution of Meniere’s disease?
Recurrent
Which common balance disorder presents intermittent symptoms?
Benign paroxysmal positional vertigo
