Illustration of brain and nervous system

Your brain contains billions of nerve cells arranged in patterns that coordinate thought, emotion, behavior, movement and sensation. A complicated highway system of nerves connects your brain to the rest of your body, so communication can occur in split seconds. Think about how fast you pull your hand back from a hot stove. While all the parts of your brain work together, each part is responsible for a specific function — controlling everything from your heart rate to your mood.