NARRATOR: A simple sneeze
can travel up to 100 miles
an hour and spray
a cloud of 100,000 germs.
Sounds gross, but sneezing
is actually a protective reflex
that's
designed to keep you healthy.
It begins when tiny nerve
endings detect something
irritating in your nose.
It could be bacteria, dirt,
dust, or other particles that
get trapped in the mucus.
The nerves transmit a signal
to your brain's sneeze center,
which in turn sends messages
to other body parts.
The abdominal and chest muscles
activate, compressing your lungs
and producing a blast of air.
Then the back of your tongue
elevates, partially closing
the passage to your mouth
and forcing the air out
through both your nose
and mouth.
[SNEEZE]
NARRATOR: And for that split
second,
your eyelid muscles are locked
shut,
making it impossible to keep
your eyes open when you sneeze.
Not all sneezes
are related to your body's
defenses.
Some people
sneeze in bright sunlight,
during exercise, or after eating
a large meal.
But the one time you'll never
sneeze?
It's when you're sleeping.
That's
because your sneeze nerves are
snoozing, too.
