Monday, 2 April 2012

What makes you dizzy when you spin?

It's not just when you spin, sometimes when you stand up too fast, or sometimes just when you're scared. But what causes that?

The answer is the Vestibular system. Okay what is the vestibular system?

Here is a picture of your ear, it looks a bit weird I know but you can make out the general shape!

The 3 canals you see make up the semicircular canal system. These make up the rotation sensitivity, so when you spin around, your brain knows because the fluid in these canals move around.

Otolithic organs

  • These are loacted in the Saccule which you can see on the right.
  • The organs contain crystals of calcium carbonate (yes chalk).
  • Crystals are attached to nerves in different positions
  • When you tilt your head or upside down, gravity pulls on these nerves telling your brain your orientation!
Back to your canals

Also in your canals are endolymph. 

This is a fluid throughout the canal. When you move, the fluid lags behind (inertia) and nerves in the canal tell your brain how you're moving.

However when you stop spinning, the endolymph continues to move (try swirling water in a cup, after you stop it still swirls) and stimulates hairs in the opposite direction.

This tells the brain that you're spinning in the opposite direction, when actually you're not- hence causing dizziness!

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