Your spinal cord functions as the communication line between your brain and your body. When you suffer an injury that bruises, tears or severs this line of communication, the messages between your head and the rest of your body are interrupted. Think of it as a loss of signal as you travel between cell phone towers. The messages back and forth from your brain to your body are the calls. When a cell phone tower goes down, calls get dropped. Of course, the bundles of nerves that make up your spinal cord are infinitely more complex, but the result remains the same -- no information gets through.