Justin has learned that the brain, spinal cord, and peripheral nerves work

together. What do they combine to form?

to allow your brain to control your body's many functions

They are all part of the nervous system.

Explanation:

The brain and the spinal cord are part of the central nervous system and the peripheral nerves are part of the peripheral nervous system. The nervous system works as the communication / control system of the body. It transmits signals throughout the body.