Physiology of balance

• balance is mediated by the vestibular nuclei in the brain stem
• the labyrinth (a part of the inner ear), is a major organ of our vestibular (balance) system
• the three semi-circular canals of the labyrinth is associated with sensing rotary motion (1)
• the brain senses the direction and speed of rotation of the head by the movement of fluid in the semi-circular canals (1)
• balance is maintained by the interactions between the labyrinth and other systems in the body, such as the visual and skeletal systems (1)
• the main inputs into the balance system are the:
  • vestibular labyrinths
  • visual system (eyes)
  • somatosensory system, especially proprioception
• the main outputs from the vestibular nuclei are:
  • vestibulo-ocular:
    • permitting reflex eye movements related to posture
  • vestibulo-spinal which supply:
    • anti-gravity muscles in the lower limbs
    • reflex arcs which control gait

Reference:

1. Information from the National Institutes of Health. Massachusetts Eye and Ear Infirmary, a teaching hospital of Harvard Medical School.