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Neuro > Vestibular System > Flashcards

Vestibular System Flashcards

1
Q

What is the purpose of the Vestibular division of CN VIII?

A

Vestibular Division of CN VIII

• Functions and Purpose

• Maintain Equilibrium

  • Hold and Regain Balance
  • Activation of Righting Responses
  • Head Position in space relative to Body
  • Normal rotation of Body Segments
  • Maintain Posture and Position Changes via integration of Primitive Reflexes

• Maintain Head Position

  • Head Righting in vertical alignment
  • Against gravity and response to motion

• Coordinate Head and Eye Movements

  • Maintain Conjugate Gaze and Visual Tracking
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2
Q

Describe the reflex integration and vestibuar system.
What are the Righting Responses?

A

Reflexes and VestibularSystem

• Primitive Reflexes integrate into Developed Motor System

  • Results in Normal Motor Movement
    • Ex. Positive Support for Stance
    • Ex. Crossed Extension for Ambulation
  • Critical for Righting and Equilibrium Responses based on an Intact Vestibular System

• Righting Responses

  • Optical Righting
    • Visual Reference- to stay upright in space
  • Labyrinthine Righting
    • Vestibular System
  • Body on Head Righting
    • Proprioceptive System- GTOs, jnt receptors
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3
Q

Describe vestibular division function and purpose to integration of systems.

A

Vestibular Division of CN VIII

• Functions and Purpose

  • Coordinates muscles and influences Muscle Tone
    • Medial and Lateral Vestibulospinal Tracts
      • Modulates Extensor Muscle Tone against Gravity
      • Critical for coordination with Visual System
      • Ex. Scooter board on incline and visual tracking

• Highly Integrated System

  • Complex pathways among: Vestibular System, Brainstem, Cerebellum, Cortical System and Visual System
  • Sensory Integration: Sensory and Vestibular Systems are the bases for all Motor, Cognitive and Emotional functions
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4
Q

Describe integration and sequence of the vestibular system.

A

Vestibular Division of CN VIII

  • Summary of Vestibular System Integration
  • Comprised of Three Afferent Sources
    • Vestibular Receptors (Inner Ear)
    • Proprioceptors (Muscles and Joints)
    • Eyes
  • Sequence
    • Vestibular Receptors orient head and body in space
    • Resultant Extensor Muscle Tone and Motor Control against gravity
    • Coordination of Eye Reflexes (VOR) and Head Movements
      • Stabilization of Visual Image on Retina in response to Head Movement
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5
Q

What are the planes of the vestibular system?

A

Planes of Vestibular System

• Definitions of…


  • Angular Acceleration (Rotational Motion): The change in speed/velocity and change in direction
    • Review of Three Dimensions in Space
    • Pitch or Up/Down motion (“Yes”) or Vertical Plane 

    • Yaw or Left/Right motion (“No”) or Horizontal Plane 

    • Roll or Left/Right Ear to Shoulder or Lateral Vertical Plane 

  • Linear Acceleration: The change in speed/velocity in a straight line and not a change in direction
    • Horizontal Plane
    • Vertical Plane 

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6
Q

What are the semicircular canals?

A

• Semicircular Canals (SC) AKA Bony Labyrinth (BL)

  • Respond to Speed and Three Dimensions (3D) in space (Head Movements)
  • Anterior (Superior) Semicircular Canals
  • Horizontal (Lateral) Semicircular Canals
  • Posterior Semicircular Canals
  • Vestibule
    • An additional portion of the SC that interconnects the SC and Cochlea
  • Layers of BL/ SC Canals
    • Bony Labyrinth Layer contains Perilymph Fluid
    • Membraneous Layer (Within Bony Labyrinth Layer) contains Endolymph Fluid
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7
Q

What are the Ampullae? Where are they?

A

Vestibular System Anatomy

• Vestibular System Receptors for Equilibrium (In Inner Ear)

  • Ampullae of the SC
    • Enlargements at end of SC Ducts 

    • Each SC Duct contains an Ampullae 

    • Each Ampullae contains Crista Ampullares 

    • Each Crista Ampullaris contains Hair Cells (when bent startsaction potential along CN VIII to Vestibular Nuclei in Brainstem) 

    • Each Crista Ampullares responds to Angular Acceleration/Rotational Motion (change in speed/ velocity and direction) 

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8
Q

What is the Vestibule?

A

Vestibular System Receptors for Equilibrium (In Inner Ear)

  • Vestibule
    • Macula of Utricle (Horizontal Plane) and responds to Linear Acceleration (change in speed)
    • Macula of Saccule (Vertical Plane) and responds to Linear Acceleration (change in speed)
    • Macula of Utricle and Saccule contain Hair Cells
      • Kinocilium and Sterocilium
      • Supported by Epithelial Cells and suspended in Gelatinous Substance containing Otoliths
      • When Otoliths bend Hair Cells, have an action potential along CN VIII to Superior and Inferior Vestibular Ganglia to Vestibular Nuclei in Brainstem
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9
Q

What are Otoliths of the Utricle & Saccule?

A

Otoliths of the Utricle & Saccule

  • Detect changes in head position relative to gravity •forward/backward and lateral flexion
  • Detect changes in linear acceleration
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10
Q

What are the tracts out the Crista & Macula to the brainstem and what are their nuclei?

A

Vestibular Nuclei of the Brainstem and Corresponding Pathways

• From Crista and Macula… (output)

  • To Lateral Vestibular Nuclei
    • Lateral Vestibulospinal Tract (Extensor Muscle Tone)
  • To Medial Vestibular Nuclei
    • Medial Vestibulospinal Tract AKA Descending Medial Longitudinal Fasciculus (DESC MLF) (Neck Muscles)
  • Superior Vestibular Nuclei
    • Ascending Medial Longitudinal Fasciculus (ASC MLF) (CN III, IV, VI for Vision)
  • Inferior Vestibular Nuclei

    • Involved with Medial Vestibulospinal Tract
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11
Q

What are the 4 locactions from the vestibular nuclei do tracts go?

A

Vestibular System Tracts and Pathways

OUTPUT PATHWAYS

From Vestibular Nuclei in Brainstem to 4 Locations…

  • Spinal Cord
    • Via Lateral Vestibulospinal Tract (LVST) and Medial 
Vestibulospinal Tract (MVST) 

    • Within Medial Vestibulospinal Tract, Fibers for Medial Longitudinal Fasciculus (MLF)
    • LVST and MVST modulate Extensor Muscle Tone via Alpha Motor Neuron (AMN) and Gamma Motor Neuron (GMN) System
  • Cerebellum 

    • Via Vestibulocerebellar Tract
    • From Vestibular Nuclei in Brainstem to Flocculonodular Lobes (balance)
  • Brainstem

    • Via Ascending Medial Longitudinal Fasciculus (ASC MLF) 
to CN III, IV, VI
  • Postcentral Gyrus AKA Primary Somatosensory Cortex 
(proprioception info)
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12
Q

What are the input pathways connect?

A

Vestibular System Tracts and Pathways

  • Connections among…Inner Ear, Brainstem, Cerebellum, Visual System, and Cortex
  • INPUT PATHWAYS
    • From Vestibular Receptors (Crista Ampullares and Macula of 
 Utricle and Saccule)
    • Along CN VIII to Vestibular Nuclei in Brainstem
    • Additional information along CN VIII to Flocculonodular Lobe 
 in Cerebellum
    • Cerebellum sends reciprocal information back to Vestibular Nuclei in Brainstem 

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13
Q

What is the VOR?

A

• Vestibulo-Ocular Reflex (VOR) Pathway

  • KEY: Mediates Eye Movement and Conjugate Eye Gaze based on changes in Head Movement and coordinates Eye with Head/Neck Movements 

  • Inputs from…

  • Visual Areas of the Cortex

  • Vestibular System

  • Pontine Reticular Formation 


• Pathway…

  • From Vestibular Nuclei of Brainstem (Superior Vestibular nuc)
  • Information travels along ASC MLF to CN III, IV, VI 

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14
Q

Summarize the MLF?

A

Summary of Medial Longitudinal Fasciculus (MLF) Pathways

  • Starts in Vestibular Nuclei of Brainstem
    • From Superior Vestibular Nuclei

      • ASC MLF to CN III, IV, VI (Vision)
    • From Medial Vestibular Nuclei
      • DESC MLF along Medial Vestibulospinal Tract (MVST) to Cervical Spinal Cord (Coordinate Head/ Neck Movements and Vestibular System)
      • From Lateral Vestibular Nuclei
        • Lateral Vestibulospinal Tract (LVST) to Spinal Cord (Mediate Extensor Muscle Tone)
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15
Q

How do you test CN VIII for nystagmus?

A

VESTIBULAR SCREENING

CN VIII Testing: Vestibular Branch

  • Observation of Nystagmus
  • Patient should be seated. 

  • Hold head in stationary position. 

  • Ask to track pen in H and X pattern. 

  • Check and note any nystagmus within and at end of ranges. 

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16
Q

How do you test CN VII for Balance & Protective Responses?

A

CN VIII Testing: Vestibular Branch

  • Balance and Protective Responses
    • Patient should be standing unsupported in front of wheelchair or mat if indicated with eyes open (Guard carefully). 

    • Observe for increased postural sway and loss of balance. 

    • Gently perturb patient’s balance (Guard carefully). 

    • Observe protective responses (postural adjustment 
or step). 

    • Repeat with eyes closed (Guard carefully). 

17
Q

How do you test CN VII for Extensor Mm Tone?

A

CN VIII Testing: Vestibular Branch

  • Observation of Extensor Muscle Tone

  • Passively move limb through full range of motion.
  • Perform Quick Stretch on limb.
  • Observe evidence of increased extensor tone (hip, knee, ankle).

Neuro (12 decks)

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