Each type of biological cells, including the simplest bacteria, receives stimuli from its environment and processes the obtained signals. Nevertheless, only metazoans, are the group whose representatives are equipped with neurons - the cells highly specialized in signal processing and transmission. In particular, only neurons are able to transmit signals over long distances. Neurons constitute multicellular structures including the most complex one which is the brain that is built not only from neurons but also from glia cells. The evolutionary development of the brain enable animals to perform intensional, not only reflexive, movements. Each consciously and intentionally initiated movement has its origin in the centers of movement control.