Considering the nervous system is the "control center" of the human body, without a functioning nervous system, there would be no way for signals to reach other organ systems in the body. An example of this can be seen with the muscular and skeletal systems. If the brain is unable to send out signals to these two organ systems, then they would cease to move or even stand up straight. Say if you were to break your spinal cord, there would be no way for the brain reach your leg muscles because the nerves in your spine are now damaged and can therefore not carry out signals from the brain.