ABSTRACT
The nervous system is made up of highly differentiated tissues, the function of which is the transmission of information. The nervous system is divided into two subsystems: the central nervous system, including the cortex, brain stem, cerebellum, and spinal cord, and the peripheral nervous system, consisting of the spinal roots, ganglia and nerves, and the peripheral nerves. With vertebrates, a further increase in the differentiation of nerve cells gives rise to a system specifically devoted to communication with the surroundings. A similar organization can still be found in olfactory cells in humans, but in the higher animals a nerve cell usually mediates the propagation of excitatory stimuli applied to other nerve or muscle cells. Thus a system of nerves is created and it is called the autonomic nervous system. This system is subdivided into two antagonist parts: the sympathetic and parasympathetic nervous systems.
