Here’s an example of how the brain, spinal cord, and peripheral nerves work together: When you sit down, your brain sends messages down the spinal cord and then to the peripheral nerves going to the muscles, telling your legs to bend and your arms to stabilize your body. Then, if you accidentally sit on a tack, peripheral nerves from your rear end send a message via the spinal cord, telling your brain that there is something painful down there. The cycle repeats itself, with the brain sending another message down the spinal cord and through the peripheral nerves, telling the legs to stand back up. Your nervous system is able to control many of these sequences for different body parts and functions continually throughout the day.