Vestibular system Flashcards Preview

Year 2 LCRS Neurology > Vestibular system > Flashcards

Flashcards in Vestibular system Deck (30)
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1
Q

Explain the structure of the labyrinth

A

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

2
Q

Where is the inner ear (labyrinth located wihtin the cranial cavity)?

A

In the petrous part of the temporal bone (one of the hardes part of the skull) for protection

3
Q

Explain the orientation of the semicircular canals in the inner ear

A

The posterior + anterior canal are located 45° anteriorly/posteriorly (form pairs–> left anterior with right posterior)

Lateral semicircular canal located laterally (about 90°)

4
Q

Explain the different types of Hair cells involved in vestibular transduction

A

Type I: (round)

  • –More in number
  • –Direct afferent, indirect efferent

Type II: (long)

  • –Direct afferents and efferents
5
Q

What are the otholit organs?

Why are they called this?

A
  • Utricule
  • Saccule

–> Because they have

Otoliths= Carbonate cristals on top of a gelaneous part that tells movements

6
Q

What are the Maculae?

Where are they located?

What is their function?

A

Maculae= areas of Utricle and Saccule where changes is posture/direction is detected –> signal sent out to vestibular system

  1. Hair cells
  2. Gelatinous matrix
  3. Otoliths = Carbonate cristals
7
Q

Explain the orientation of the Macula within the utricle and the saccule

A

In utricle: on bottom: they detect horizontal movement

In Saccule–> at side of saccule –> detect vertical movement

8
Q

What is the striola?

A

the site within the maculae where opposing hair bundle polarities to allow movement in any direction

9
Q

Explain the function of the ortholids

A

They move sideways during movements –> evoke pressure on different areas–> conducted into AP

10
Q

What is the analogue structure of the maculae in the ortheloid organs in the semicircular canals?

A

The Hair cells are located in the Ampulla (enlargement of semicircular canals), to be more specific in the Ampullary Crista

11
Q

What is the Cupula?

What is its role?

A

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
12
Q

What are the Kinocilia?

What is their orientation?

A

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

13
Q

Where does the inner ear gets its blood supply from?

A

labyrynthine

From the anterior iferior cerebellar artery

branch of basilic

14
Q

Where does primary afferent information from the vestibular system (labyrinth end?)

What is its organisaion?

A

Going into the vestibulochochlear nucleus

Lateral inferior: information in the Static labyrinth (otoliths)

Superior and medial: infomation of Kinetic labyrinth (SCC)

15
Q

Where do projections from the vestibular nucleus go to?

A

–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

16
Q

What is the importance of the vestibulocerebellar pathways?

A

Movement coordination

Posture regulation

VOR modulation –> vestibulo occular reflexes

17
Q

Explain the role of the thalamus and the cortex in vestibular processing of information

A
  • 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

18
Q

In which part of the cerebellum is vestibular information processed?

A

In the vestibulocerebellumn (flucconodular node)

19
Q

Explain the role of the cerebellum in central processing of information in the vestibular system

A
20
Q

How do action potentials change in movement in comparison to resting/no change in movement?

A

Normally: bassal fiereing rate

Dependant on direction of movement–> increase or decrease of fiereing rate the processing tells brains afterwards where the movement goes

21
Q

What kind of movents are detected by the orthicle organs?

A
  • Linear acceleration and tilt: otolithmovement
  • Otolith movement causing depolarisation or hyperpolarisation
22
Q

Which kind of mevements are detected by the semicircular canals?

A
  • Angular acceleration
  • Superior and Inferior SCC: (+) Away fromUtricule
  • Horizontal SCC: (+) Towards the Utricule
23
Q

Explain the two major vestibulospinal refelxes tracks to skeletal muscle

A

•Lateral vestibulo spinal tract

–Ipsilateral

–Motor neurons to limb muscles

•Medial vestibulospinal tract

–Bilateral

–Motor neurons to neck and back muscles

24
Q

Explain the function and the pathways for vestibulo occular pathways

A
  • žFunction: To keep images fixed.
  • žConnection between vestibular nuclei and oculomotor nuclei.
  • ž5 - 7 msec latency
  • žEye movement in opposite direction to head movement.
25
Q

How do you investivate someome with vertigo disturbance?

A

—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)

—

26
Q

What is vertigo?

A

•: Illusion of movement

– usually rotational or ‘true vertigo’

27
Q

What is •Unsteadiness?

A

off balance= BVF

28
Q

What are the symptoms for someone experiencing problems with the vestibular system

A

•Vertigo: Illusion of movement

– usually rotational or ‘true vertigo’

  • Dizziness, giddiness: more vague
  • Unsteadiness: off balance= BVF
  • Self –motion perception
29
Q

What are examples for problems wtith the vestibular system?

A
  • Acute
    • Vestibular Neuritis (‘labyrinthitis’)
    • Stroke
  • Intermittent:
    • Benign Paroxysmal Positional Vertigo (BPPV)
  • Recurrent
    • Meniere’s Disease - rare
    • Migraine - common
  • Progressive:
    • Acoustic Neuroma (8th nerve)
    • Degeneration
30
Q

Explain the Vestibulo-occular reflex pathway

A
  1. Efferent information to vestibulocochlear nucleus
  2. Information synapse to both Abducens nuclei (VI) and causes
    • Ipsilateral excitation
    • Contralateral inhibition
  3. From the Abducens nucleus 2 signals go out
    1. To the Lateral rectus muscle (excitory/inhibitory respective to 2.)
    2. To the contralateral Nucleus of CNIII
  4. CNIII nucleus sends out signals to the medial recuts muscle and caues contraction/relaxation