GRABBING A SMALL OBJECT, SUCH AS AN APPLE, MAY SEEM AUTOMATIC AND EASY. BUT FEW PEOPLE CONSIDER THE COMPLEX BIOLOGICAL MECHANISM UNDERLYING THIS SIMPLE ACT. NEURONS IN THE BRAIN INSTANTLY FIRE IN PATTERNS THAT SEND COMMANDS DOWN THE SPINAL CORD. THESE COMMANDS ARE RELAYED TO MUSCLE TISSUE IN THE ARM. THE TISSUE CONTRACTS, RAISING THE ARM, EXTENDING AN ELBOW, OR FLEXING THE WRIST AND FINGERS. FOR SOME PEOPLE WITH SPINAL CORD INJURIES, THOSE COMMANDS ARE HINDERED BY THEIR DAMAGED NERVOUS SYSTEMS. THEIR BRAINS ARE NO LONGER ABLE TO SEND MESSAGES THROUGHOUT THEIR BODIES. FOR THESE PEOPLE, THESE ACTIONS MAY REQUIRE SUBSTANTIAL EFFORT OR BE COMPLETELY IMPOSSIBLE.
