An electric shock can be enough to stop the human heart.
But another controlled blast of electricity can also restart it.
Because movements in the human body are triggered by natural electrical pulses, electricity can be a useful tool in medicine.
Take, for instance, the heart.
The heart has a natural pacemaker that sends out electrochemical signals - which controls what we know as our heartbeat.
An electric shock upsets this heartbeat.
Surgeons use electricity in some operations to stop the heart from beating.
Complex machinery simulates the functions of key organs - like the heart and lungs - to keep the patient alive.
Mr Philip Belcher, Heart Surgeon, UK - "We are now going to apply an alternating current to the heart at 20 volts from about 10 milliamps... as you can see as it's applied the heartbeat stops."
This makes it easier for the surgeons to operate.
Mr Philip Belcher, Heart Surgeon, UK - "Now we are going to make the heart beat again by shocking it with a direct current shock... fire please. "
The direct current shock returns the heart to its regular beat.
Electrical impulses also control muscle movement in the body.
These impulses can be seen on a machine called an oscilloscope.
Dr Tony Barker, Medical Physicist, UK - "At the moment my muscle is relaxed so there is virtually no electrical activity in it whatsoever. If I choose to move my little finger you can see there is a large amount of electrical activity there, as my brain tells my finger to move. It just so happens that these electrical signals occur at frequencies that the human ear can hear, so you can connect them to a loudspeaker and actually listen to your muscles. Now that's quite a useful technique because doctors can have their ears trained to diagnose muscle disorders by listening to abnormalities in the sounds from muscles."
For doctors, electricity offers the possibility to manipulate and monitor the electrical currents in the body - and save many lives.