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Concept Spotlight: The Vestibular Apparatus

by Ellen on September 8th, 2016

In last week’s Quote of the Month, we talked about our unnamed sixth sense, the kinesthetic sense. This is the sense that gives you information about your self and your relationship to the space around you. Have you ever stopped to wonder how it is that you can instantly know your relationship to gravity, even with your eyes closed and your body suspended? “How You Stand, How You Move…” by Missy Vineyard answers this question by explaining the mechanics of your vestibular sense. She suggests that this be considered the seventh sense, unique and distinct from the movement sense, though it can just as easily be considered part of the same sense of yourself relative to external space.

The vestibular apparatus is comprised of several tiny, fluid-filled tubes in the head whose inside walls are covered with tiny hairlike receptors. As you move, the fluid pushes on the receptors in various parts of the tubes, and the information is sent to the brain and interpreted as movement of the head in space. The apparatus also includes two small basins of fluid, each of which has particles of calcium within the fluid. Moving your head jostles these basins (like shaking a snow-globe) and causes the calcium particles to slowly fall through the fluid towards gravity. They land on the inner walls of the basin, where sensory receptors pick up the location of the particles and send that info to the brain, which interprets it as the location of gravity relative to the head. This apparatus seems at once elegant and simple – how do you tell what direction gravity is? Drop something!

This, incidentally, is why dancers learn the technique of ‘spotting’ – when doing multiple turns, a dancer attempts to keep her head still for as long as possible before whipping around to focus on the same spot as quickly as she can. This keeps the fluid within the vestibular apparatus from sloshing too much, and allows her to train her senses to compensate for the remaining slosh and prevent her from getting dizzy. After all, while the snow-globe is shaking the snow within it doesn’t know which way is up; it’s only once the fluid settles that it finds the direction of fall. We’ll talk more about spotting next week in our Everyday Poise.

Forward and Up! is a Pittsburgh-based private practice offering quality instruction in the Alexander Technique in a positive and supportive environment.

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