Explain The Nervous System Among Different Animals?

The nervous system consists of neurons which help in the conduction of impulse and the coordination of body functions. Sponges do not possess it. Coelenterates have primitive type of nervous system. The nervous system is ring shape and lies around the front part of alimentary canal in flat and round worms. The nervous system is also ring shape in annelids and arthropods and lies around the front part of alimentary canal and has a nerve cord with ganglia. Molluscs have nervous tissue which has ganglia, connectives and commissures. The connection between ganglia is established by commissures. Ganglia are present in connectives. Echinoderms have two nerve rings including radial nerve. The chordates have hollow nervous system which is dorsally placed. The vertebrates have three divisions of nervous system which includes central nervous system, peripheral nervous system and autonomic nervous system. Brain and spinal cord constitute the central nervous system. Brain is present in the cranium which is also known as brain box. The spinal cord is situated in the neural canal of back bone which is also known as vertebral column. The central nervous system forms the peripheral nervous system by the nerves arising from them. The peripheral nervous system includes the cranial and spinal nerves. The cranial nerves arise from cranium and the spinal nerves arise from spinal cord. The autonomic nervous system includes the sympathetic and parasympathetic nervous system.