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Vestibular System

Vestibular System. To maintain balance and maintenance of gaze (eye position) and posture (skeletal position). Requires 2 out of 3 components: inner ear, vision, and/or proprioception (position of joints, limbs)

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Vestibular System

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  1. Vestibular System To maintain balance and maintenance of gaze (eye position) and posture (skeletal position). Requires 2 out of 3 components: inner ear, vision, and/or proprioception (position of joints, limbs) Utricle detects linear acceleration, using otoliths (“ear stones”, calcium carbonate crystals) as inertial mass to detect gravity and starting/stopping during linear motion. Semicircular Canals detect rotational acceleration in each of 3 planes. Sloshing of endolymph around the canal; deforms cupula which bends hair cells. Loss of inner ears -> inability to detect gravity, rotation. Conflict Hypothesis of Motion Sickness When inputs to vestibular system don’t agree with each other, causes dizzyness and nausea e.g. reading book in bumpy car: visual field is steady, but inner ear reports accelerations T

  2. Fox Figure 10.17

  3. “bouncing, rocking” “not moving” Motion Sickness Fox Figure 10.17

  4. Vestibular Apparatus = “Labyrinth” Vestibulocochlear Cranial Nerve 8 Fox Figure 10.12

  5. Utricle • detection of • linear acceleration

  6. Gravitational force see Fox Figure 10.15

  7. Figure 10.15

  8. Semicircular Canals • detection of • rotational acceleration

  9. Figure 10.16

  10. Central Vestibular Pathway

  11. Function: fixate line of sight on visual target during head movement Mechanism: senses rotations of head, commands compensatory movement of eyes in opposite direction Connections from semicircular canals, to vestibular nucleus, to cranial nerve nuclei  excite extraocular muscles The Vestibulo-Ocular Reflex (VOR)

  12. Vestibular Connections Mediating Horizontal Eye Movements

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