Evolution

Evolution 

In the course of evolution and with the higher development of individual departments of the animal kingdom is a clear trend towards concentration and associated specialization of parts of the nervous system noted. While in primitive animals, yet some individual neurons fall special functions (eg pacemaker neurons, the clock for elementary body movements of worms pretend), to perform highly complex nervous systems of up to several billions of interconnected neurons in specific tasks. 

In nervous systems with Zentralganglien the conduction of neurons in Afferenzen (from the sensors to the brain) and Efferenzen (from effectors to the brain, muscles, for example) are divided.