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The Vestibular System

The Vestibular System. Lesson 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

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The Vestibular System

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  1. The Vestibular System Lesson 18

  2. 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 ~

  3. Receptors for Orientation • Inner ear • Gravity detectors • plane of reference • Mechanoreceptors • Vestibular Organs • otocysts • saccule • utricle • semicircular canals ~

  4. Otocysts • Liquid-filled “ear sacs” • lined with hair cells • contain otoliths • “ear stones : direction of acceleration • saccule: vertical movement • utricle: horizontal movement ~

  5. Acceleration to right tilted At rest Direction of gravity

  6. 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 ~

  7. Ampulla Crista hair cells Cupula Semicircular canals Utricle

  8. 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) ~

  9. 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 ~

  10. Visual Illusions of Movement • Self vection • perceive you are moving, but not • 2 adjacent trains, cars • restricted visual field • no background information ~

  11. Visual Illusions of Movement • Postural sway • visual cues help maintain posture • illuminated booth, that can sway • individual sways with surroundings • no vestibular stimulation ~

  12. 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 ~

  13. 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 ~

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