The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord, which coordinate incoming and outgoing information. The PNS connects the CNS to organs and sensory receptors, carrying signals to and from the CNS. Neurons are the basic functional units and come in sensory, motor, and interneuron types that differ in their dendrite and axon structures. Sensory neurons carry signals to the CNS while motor neurons carry signals away, and interneurons connect signals within the CNS.