The Nervous System
The nervous system is a highly complex network of neural cells (neurons) and supportive (glial) cells responsible for internal coordination.
The fundamental functions of the nervous system fall under:
-  Sensory functions: Gathers information from outside and within the body and relays it to the brain. 
-  Integrative functions: Information is received, processed, stored, and retrieved. 
-  Motor functions: Signals are sent from the brain to the muscles, organs, and glands where an effect is produced (for example, movement of a limb or secretion of gastric acid). 

Figure 1: The Nervous System
The nervous system has two major anatomical subdivisions:
-  Central Nervous System (CNS): Brain and Spinal cord 
-  Peripheral Nervous System (PNS): Nerves and ganglia