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~BN18 vestibular system.ppt
 

~BN18 vestibular system.ppt

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    ~BN18 vestibular system.ppt ~BN18 vestibular system.ppt Presentation Transcript

    • The Vestibular System Lecture 18
    • Orientation: The Vestibular System
      • Position & motion of body in space
        • critical for adaptive interaction
        • largely unnoticed
        • except unusual conditions
          • motion sickness: nausea, dizziness
      • Maintenance of balance & posture
        • coordinating body position with other sensory information ~
    • Receptors for Orientation
      • Inner ear
      • Gravity detectors
        • plane of reference
      • Mechanoreceptors
      • Vestibular Organs
        • otocysts
          • saccule
          • utricle
        • semicircular canals ~
    • Otocysts
      • Liquid-filled “ear sacs”
        • lined with hair cells
        • contain otoliths
          • “ ear stones : direction of acceleration
      • saccule: vertical movement
      • utricle: horizontal movement ~
    • At rest Direction of gravity tilted Acceleration to right
    • Semicircular Canals
      • Rotary acceleration
        • direction & extent of circular movement
          • any direction
      • 3 fluid-filled canals
        • right angles to each other
        • 1 for each major plane
      • Movement causes fluid to circulate
        • displaces cupula ~
    • Semicircular canals Utricle Ampulla Crista hair cells Cupula
    • Vestibular Pathway
      • Vestibulocochlear nerve (VIII)
        • Some axons directly to cerebellum
      • Most axons to medulla
          • vestibular nuclei
        • cerebellum, spinal cord, medulla & pons
        • motor nuclei for eyes (III, IV, & VI)
          • compensates for movement of head
        • temporal cortex (dizziness) ~
    • Vestibular Stimulation
      • Perceive movement in an airplane?
        • No, persisting passive movement
        • Otoliths, fluid move at same speed
      • Vestibular system detects active movements
        • changes in rate of motion
          • acceleration
      • heating/cooling fluid  perception of body motion ~
    • Visual Illusions of Movement
      • Self vection
        • perceive you are moving, but not
        • 2 adjacent trains, cars
        • restricted visual field
          • no background information ~
    • Visual Illusions of Movement
      • Postural sway
        • visual cues help maintain posture
        • illuminated booth, that can sway
        • individual sways with surroundings
        • no vestibular stimulation ~
    • Motion Sickness
      • During passive transportation
          • e.g. riding in car, but not when driving
        • unusual circumstances
          • e.g amusement park rides
        • usually not steady motion
      • Symptoms: nausea, dizziness, vertigo, cold sweats, hyperventilation ~
    • Cause of Motion Sickness
      • Sensory conflict theory
        • Mismatch b/n visual & vestibular info
      • Treisman (1977): cause of vomiting
        • ingestion of natural toxins disrupt visual input & motor coordination
        • vomiting adaptive response to inappropriate stimulus: toxins/motion
      • Dogs: remove vestibular system
        • toxins  no vomiting ~