VESTIBULAR SYSTEM Flashcards
(53 cards)
What are the 3 main inputs of the vestibular system?
Visual, proprioceptive and vestibular (rotation and gravity) information
What are the outputs of the vestibular system?
Mainly reflexes to maintain a stable posture and stable gaze
Where is the vestibular organ located?
Posterior area of the inner ear called the labyrinth
Describe the structure of the vestibular organ
Utricle and saccule located in vestibule and joined together by conduit. Saccule also joined to cochlea by conduit.
Each ear also has 3 semicircular canals which have an ampulla on one side and are connected to the utricle
What are the 3 semi-circular canals called?
Anterior semi-circular canal
Lateral semi-circular canal
Posterior semi-circular canal
How is the labyrinth positioned in the skull?
Superior projection on base of skull
How is specific head movement distinguished by the vestibular organ?
The orientation of the semi-circular canals draws planes. A movement in each plane will stimulate the structures giving a map of how the head is moving.
The utricle, saccule and the 3 semi-circular canals gives 5 structures which work independently
What is the largest cilium on vestibular hair cells called?
Kinocilium
How is movement of the head sensed?
Movement of head causes movement of endolymph which shifts the hair cell’s cilia. The bigger the movement the bigger the depolarisation/hyperpolarisation
If stereocilia move towards the kinocilium the cell depolarises and vice versa.
Which organs of the vestibular organ are otolith organs?
Utricle and saccule
What are otoliths and what do they do?
Calcium carbonate crystals located on top of hair cells and gelatinous matrix. They help to deflect the hairs by adding weight
What does the maculae contain and where is it located?
Contains the hair cells, a gelatinous matrix and otoliths on top.
Horizontal in the utricle and vertical in the saccule
Where are the hair cells in the semi-circular canals located?
Ampulla - rest of the canal only has endolymph
Describe the structure of the ampullas
Hair cells located in the crista.
Cells surrounded by the cupula.
One end of ampulla leads to semi-circular canal and other end to the utricle
What sit the cupula?
Gel like substance surrounding the hair cells of the ampulla (canals) which helps with hair cell movement
Describe the planes formed by the canals
Anterior and posterior canals/planes form a 90 degree angle with the lateral canal/plane horizontal to them
Where do primary vestibular afferents from hair cells end/lead to?
Vestibular nuclei in the brainstem
Cerebellum for coordination and feedback
Where does the vestibular nuclei project to?
Spinal cord
Nuclei of the extraocular muscles (eye movement)
Cerebellum
Centres of cardiovascular + respiratory control
Where is the vestibular cortex located?
Not one specific area since many inputs and integrators involved spread over many cortical areas
What/where is the main processing centre of the vestibular system located?
Parietal lobe, in the Parieto-Insular Vestibular Cortex (PIVC)
What are then 3 functions of the vestibular system?
Detect and inform about head movements
Keep images fixed in retina during head movements
Postural control
How does the head know if it is not moving?
Hair cells have resting potential which gives a basal discharge to the nerve
What causes otolith movement?
Linear acceleration and tilt
What type of movement is the utricle sensitive to?
Horizontal movement e.g. travelator
maculae is horizontal
