It is asystem of nerve fibers and ganglia which control and cordinate the involuntary activities of the visceral organs,such as secretion of digestive fluid,action of heart,etc.this system is autonomic in the sense that it regulatessuch activities of the body in which the will power of the animal is not involved.For example the secretion of the digestive fluid is always under the control of autonomic nervous system,but the animal is not aware of it.

The autonomic nervous system is divide into----(1) sympathetic nervous system and(2) parasympathetic nervous system.


It consists of two longitudinal sympathetic cords,one on either side of the vertebral column ventral to the dorsal aorta,which run forward along the outer sides of the systemic arches.each cord bears  at intervals small black nine to ten sympathetic ganglia connected with the corresponding spinal nerves by the ramous communicans.


There is no much cord or ganglia as found in the sympathetic nervous system.It consists of very small parasympathetic ganglia situated in the walls of the visceral organs and nerve fiberes.these are connected with the central nervous system after travelling in some cranial and spinal nerves.For example it slows heart beats.

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