The Human Brain : From Neurone to Nervous System

VESTIBULAR APPARATUS AND BALANCE. VESTIBULO-OCULAR REFLEXES


  1. Objects fall over if the centre of gravity is outside the base of the object; (the centre of gravity is the point through which the force of gravity acts). In the body, adjustments of the distribution of forces generated by muscles (‘Muscle Tone’) keep the line of gravity within the base.

  2. Reflexes influencing balance. The sensory input that influences these adjustments comes from several sources:
    • the inner ear (utricle and saccule) senses the direction of gravity - the position of the head in space
    • the inner ear (semicircular canals) senses the direction of rotation or acceleration of the head, and provides some rapid dynamic responses
    • muscle, tendon and joint receptors sense joint the position of the limb
    • the eyes sense the visual environment, e.g. the horizon, and the distance of objects

  3. Vestibulo-Ocular reflexes are important in adjusting the position of the eyes so that a constant visual environment may be maintained during head movements.






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