Vestibular System Flashcards
What is the main function of the vestibular system
- Responsible for maintaining our balance, posture and spatial orientation
what are the 3 receptor systems that the vestibular system integrates
- The eyes
- General proprioceptive(muscle, joints and tendons) and cutaneous receptors
- Vestibular receptors in the inner ear (the vestibular apparatus)
what is the inner ear made out of
- The labyrinth
- Vestibular apparatus
- Cochlear
What are the two types of fluid within the labyrinth
- endolymph
- perilymph
what is the difference between the endolymph and perilymph
Endolymph
- High in potassium low in sodium
Perilymph
- Low in potassium high in sodium
- this allows the vestibular cells to function and establish the end-cochleae potential
what is the labyrinth divide into
The labyrinth contains an auditory part and a vestibular par
What is present the vestibular part of the labyrinth
In the vestibular part, there are 3 semicircular ducts (posterior, anterior and lateral)
- these lie 90 degrees to each other
what activates the cells int he semicircular ducts
Movement of endolymph inside may activate the cells in the duct, depending on the position of the head.
what is also present in the vestibular part
there is also the utriculus and the sacculus.
What are present in the utriculus and sacculus
Present in these are small protrusions where the vestibular cells lie.
what do vestibular cells have
The vestibular cells have many cilia(stereocilia and kinocilia), which depending on movement cause hyperpolarisation or depolarisation of the cell by releasing glutamate.
What is present in the ampulla
Inside the ampulla, there is a gelatinous substance called the cupula where the cilia are embedded.
movement of the cupola….
causes movement of the cilia
what is the difference between the ampulla, utricular and saccule
In the ampulla there is cupola which embeds the cilia whereas In the utricular and saccular maculae, there are also cilia cells but they are slightly different due to the presence of otoconia (calcium crystals which provide gravitational stimulation).
what do the hair cells of the articles and saccule work together to produce
The hair cells of the utricles and saccule work together to provide a 3-dimensional representation of direction of linear force.
describe the difference between the trickles and saccule
In the utricles, hair cells are polarized (excited) towards the striola. Provides horizontal encoding.
In the saccules, hair cells are polarized away from the striola
What are striola
- narrow central area of the utricular macula where the orientations of the tallest stereocilia and kinocilia change).
- Provides vertical encoding.
describe how the vestibular-ocular reflex and nystagmus is activated
Activation of vestibular cells —> activation of vestibular neurones —> extraocular motor neurones —> eye muscles —> compensatory eye movements to fix a visual target (opposite to the direction of movement)
name the 4 vestibular nuclei
superior, medial, lateral and descending vestibular nucle
describe where signals from the labyrinth go
From the labyrinth, afferent signals enter the 4 vestibular nuclei (superior, medial, lateral and descending vestibular nuclei). Signals then reach 3 major destinations and 1 important destination.
- Spinal cord through the vestibulospinal tract
- Reticular formation
- Superior colliculus and eye muscle nuclei
- Medial cerebellar nucleus to control balance (see diagram in more detail showing flocculonodular lobe).
what are the efferent outputs for the labyrinth
- Spinal cord through the vestibulospinal tract
- Reticular formation
- Superior colliculus and eye muscle nuclei
- Medial cerebellar nucleus to control balance (see diagram in more detail showing flocculonodular lobe).
what is kinetosis
disagreement exists between visually perceived movement and the vestibular system’s sense of movement.
What is meunière disease
a disease of unknown cause affecting the membranous labyrinth of the ear, causing progressive deafness and attacks of tinnitus and vertigo.
what is benign paroxysmal positional vertigo
one of the most common causes of vertigo — the sudden sensation that you’re spinning or that the inside of your head is spinning.
- Within the labyrinth of the inner ear lie collections of calcium crystals known as otoconia or otoliths.
- In patients with BPPV, the otoconia are dislodged from their usual position within the utricle, and migrate over time into one of the semicircular canals.
- Dislodging the otoconia (‘ear rocks’) causes abnormal endolymph fluid displacement and a resultant sensation of vertigo.
describe how to do the hall pike manoeuvre
- Patient sitting, turn head 45 degrees to face you and observe patients eyes for 30 seconds.
- The clinician helps the patient to lie down backwards quickly, with the patients head hanging off slightly from the bed.
- The patient’s eyes are then observed for about 45 seconds as there is a characteristic 5–10 second period of before the onset of nystagmus.
What are the symptoms of vestibular issues
- Nystagmus
- Nausea
- Dizziness
- Disequilibrium
- Vertigo
What are the causes of vestibular issues
- Nerve/inner ear infections
- Tumours
- Vascular insufficiency
- Trauma
- Endolymph imbalance
How do you test for balance disorders
- Eye movements
- Claroic testsing
- Hallpike manoeuvre
Name tests for the vestibular
(1) Videonystagmography
(2) Electronystography (ENG)
(3) Posturography, Bárany chair
