Steven, 14, was diagnosed with spinal muscular atrophy (SMA) when he was 3 years old. Even though his condition makes it hard to get around, he has found a way to play the sport he loves — and he lives to surprise people. Back to Articles Related Articles Brain and Nervous System If the brain is a central computer that controls all the functions of the body, then the nervous system is like a network that relays messages back and forth to different parts of the body. Find out how they work in this Body Basics article. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.