Your nervous system is organized into two broad anatomical divisions: the central nervous system (consisting of the brain and spinal cord) and the peripheral nervous system (PNS). Your PNS is further organized into two functional divisions. If you tap your knee, the signal to act is carried via your to the muscles in your knee. In contrast, the signals that pass via the are involuntary and act primarily to regulate your body's internal environment. This involuntary nerve are system is further organized into three divisions. If you need a sudden burst of energy, your is activated to help you act quickly. In contrast, if you are relaxing and conserving energy, that is your that is primarily in action. The third division is your which helps control the components of the digestive system.