Vestibular system Flashcards
Explain the structure of the labyrinth
Saccula is connected to Utricle and Chochlear
Connected to Utricle: Semicircular canals (connected anterior and posterior + independant lateral semicircular canal)
Ech of the canals has thickenings Ampulla
Where is the inner ear (labyrinth located wihtin the cranial cavity)?
In the petrous part of the temporal bone (one of the hardes part of the skull) for protection
Explain the orientation of the semicircular canals in the inner ear
The posterior + anterior canal are located 45° anteriorly/posteriorly (form pairs–> left anterior with right posterior)
Lateral semicircular canal located laterally (about 90°)
Explain the different types of Hair cells involved in vestibular transduction
Type I: (round)
- –More in number
- –Direct afferent, indirect efferent
Type II: (long)
- –Direct afferents and efferents
What are the otholit organs?
Why are they called this?
- Utricule
- Saccule
–> Because they have
Otoliths= Carbonate cristals on top of a gelaneous part that tells movements
What are the Maculae?
Where are they located?
What is their function?
Maculae= areas of Utricle and Saccule where changes is posture/direction is detected –> signal sent out to vestibular system
- Hair cells
- Gelatinous matrix
- Otoliths = Carbonate cristals
Explain the orientation of the Macula within the utricle and the saccule
In utricle: on bottom: they detect horizontal movement
In Saccule–> at side of saccule –> detect vertical movement
What is the striola?
the site within the maculae where opposing hair bundle polarities to allow movement in any direction
Explain the function of the ortholids
They move sideways during movements –> evoke pressure on different areas–> conducted into AP
What is the analogue structure of the maculae in the ortheloid organs in the semicircular canals?
The Hair cells are located in the Ampulla (enlargement of semicircular canals), to be more specific in the Ampullary Crista
What is the Cupula?
What is its role?
Cupula is a Gelatinous projection within the Crista of the Ampulla of the semicircular canal
- –> Movement moves Endolymph
- Endolymph moves
- the cupula and
- the cupla moves the hair cells
What are the Kinocilia?
What is their orientation?
It is the longest projection of the Hair cells
–> are oriented in the same direction on each side of the head to mirrow the split between the two ears
Generieren das Rezeptorpotential
Abscherung der Stereocilien in Richtung zum Kinocilium → Zunahme der Erregung
Abscherung der Stereocilien in Gegenrichtung zum Kinocilium → Abnahme der Erregung
Where does the inner ear gets its blood supply from?
labyrynthine
From the anterior iferior cerebellar artery
branch of basilic
Where does primary afferent information from the vestibular system (labyrinth end?)
What is its organisaion?
Going into the vestibulochochlear nucleus
Lateral inferior: information in the Static labyrinth (otoliths)
Superior and medial: infomation of Kinetic labyrinth (SCC)
Where do projections from the vestibular nucleus go to?
–spinal cord (vesibulospinal reflexes)
–nuclei of the extraocular muscles (vestibulo-occlear reflex–> eye movement integrate with head movement)
–Cerebellum (vesibulocerebellar reflexes)
–Centers for cardiovascular + respiratory control
What is the importance of the vestibulocerebellar pathways?
Movement coordination
Posture regulation
VOR modulation –> vestibulo occular reflexes
Explain the role of the thalamus and the cortex in vestibular processing of information
- Vestibular nuclei: project to thalamus
- Thalamic nuclei: project to the head region of the primary somatosensory cortex
And superior parietal cortex: ‘vestibular cortex’ concerned with spatial orientation (orientations of obects in space)
•Cortical projections may account for feeling of dizziness (vertigo) during certain kinds of vestibular stimulation
In which part of the cerebellum is vestibular information processed?
In the vestibulocerebellumn (flucconodular node)
Explain the role of the cerebellum in central processing of information in the vestibular system
How do action potentials change in movement in comparison to resting/no change in movement?
Normally: bassal fiereing rate
Dependant on direction of movement–> increase or decrease of fiereing rate the processing tells brains afterwards where the movement goes
What kind of movents are detected by the orthicle organs?
- Linear acceleration and tilt: otolithmovement
- Otolith movement causing depolarisation or hyperpolarisation
Which kind of mevements are detected by the semicircular canals?
- Angular acceleration
- Superior and Inferior SCC: (+) Away fromUtricule
- Horizontal SCC: (+) Towards the Utricule
Explain the two major vestibulospinal refelxes tracks to skeletal muscle
•Lateral vestibulo spinal tract
–Ipsilateral
–Motor neurons to limb muscles
•Medial vestibulospinal tract
–Bilateral
–Motor neurons to neck and back muscles
Explain the function and the pathways for vestibulo occular pathways
- Function: To keep images fixed.
- Connection between vestibular nuclei and oculomotor nuclei.
- 5 - 7 msec latency
- Eye movement in opposite direction to head movement.
How do you investivate someome with vertigo disturbance?
Anamnesis
Cranial nerves
Balance and Gait assessment
Cerebellum
Gaze assessment: eye movements.
Vestibular tests:
- ◦Caloric test
- ◦vHIT
- ◦VEMP
- ◦Rotational test
Imaging: CT Scan, MRI
Subjective assessment (questionnaires)
What is vertigo?
•: Illusion of movement
– usually rotational or ‘true vertigo’
What is •Unsteadiness?
off balance= BVF
What are the symptoms for someone experiencing problems with the vestibular system
•Vertigo: Illusion of movement
– usually rotational or ‘true vertigo’
- Dizziness, giddiness: more vague
- Unsteadiness: off balance= BVF
- Self –motion perception
What are examples for problems wtith the vestibular system?
- Acute
- Vestibular Neuritis (‘labyrinthitis’)
- Stroke
- Intermittent:
- Benign Paroxysmal Positional Vertigo (BPPV)
- Recurrent
- Meniere’s Disease - rare
- Migraine - common
- Progressive:
- Acoustic Neuroma (8th nerve)
- Degeneration
Explain the Vestibulo-occular reflex pathway
- Efferent information to vestibulocochlear nucleus
- Information synapse to both Abducens nuclei (VI) and causes
- Ipsilateral excitation
- Contralateral inhibition
- From the Abducens nucleus 2 signals go out
- To the Lateral rectus muscle (excitory/inhibitory respective to 2.)
- To the contralateral Nucleus of CNIII
- CNIII nucleus sends out signals to the medial recuts muscle and caues contraction/relaxation
