Stun Guns

On th­e old "Star Trek" series, Captain Kirk and his crew
never left the ship without their trusty phasers. One of the
cooles­t things about these weapons was the "stun" setting.
Unless things were completely out of control (as they
frequently were), the Enterprise crew always stunned their
adversaries, rendering them temporarily unconscious, rather
than killing them.

We're still a ways off from this futuristic weaponry, but
millions of police officers, soldiers and ordinary citizens
do carry real-life stun weapons to protect against personal
attacks. Like the fictional phasers of "Star Trek," these
devices are designed to temporarily incapacitate a person
without doing any long-term damage.

The Body's Electrical System

We tend to think of electricity as a harmful force to our
bodies. If lightning strikes you or you stick your finger in
an electrical outlet, the current can maim or even kill you.
But in smaller doses, electricity is harmless. In fact, it is
one of the most essential elements in your body. You need
electricity to do just about anything.

When you want to make a sandwich, for example, your brain
sends electricity down a nerve cell, toward the muscles in
your arm. The electrical signal tells the nerve cell to
release a neurotransmitter, a communication chemical, to the
muscle cells. This tells the muscles to contract or expand in
just the right way to put your sandwich together. When you
pick up the sandwich, the sensitive nerve cells in your hand
send an electrical message to the brain, telling you what the
sandwich feels like. When you bite into it, your mouth sends
signals to your brain to tell you how it tastes.

In this way, the different parts of your body use electricity
to communicate with one another. This is actually a lot like
a telephone system or the Internet. Specific patterns of
electricity are transmitted over lines to deliver
recognizable messages.