That's a great question (and it's something that I
used to do all the time when I was younger!). In
our inner ears (inside our eardrums in our heads),
we have a series of canals that give us
information about the position of our head in
space. It's how you know which way your head
moving (like to the right or left, up or down),
even if our eyes are closed. Basically, these
canals are arranged in half-circles and are filled
with a liquid. The insides of the canals (the
part with the liquid) have lots of little
hair-like projections, each of which is in turn
connected to a nerve cell. When we move our head,
the liquid in the canals moves as well, and the
movement of the liquid moves the hair-like
projections, sort of the like how the hair on your
arms moves when you put them under running water.
As the hair-like projections move in the liquid,
they trigger the nerves. The nerves then send all
of this information to the brain, and the brain
processes all of it and gives you the sensation of
knowing which way your head is moving. Pretty
Anyway, this is what happens
when we are moving around normally. When you spin
your head around a lot, the liquid in these canals
get moving really fast too, moving all of the
hair-like projections very fast, triggering all of
the nerves all at once and over and over again.
Pretty soon everything is moving so fast that the
nerve cells and the brain can't keep up with all
of the information from the motion. Basically,
you have overloaded the ability of the nerve cells
and the brain to process all of this information.
The brain can't deal with all the information
it's getting, and you feel dizzy. Since your
brain isn't sure which way is up, it can't tell
your body which muscles it needs to use to stand
upright, you fall down. As you lie on the ground,
the nerve cells and the brain recover (helped by
the fact that the liquid has finally stopped
moving so fast) and you begin to correctly feel
which way is up again.
Then you can get up
and do it again if you want!
I hope this
answers your question.
We have acceleration detectors in our inner
earcavities that function as direction-sense
mechanisms.By changing the orientation of your
head very quickly, you will lose your instinctual
sense of which way isup and which way is down,
which will cause you to loseyour balance.
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