The neural system is the control system of the body which consists of highly specialized cells called neurons. The neurons detect and receive information from different sense organs (receptors) in the form of stimuli and transmit the stimuli to the central neural system (CNS) through sensory nerve fibres. The central neural system is composed of the brain and spinal cord.
Thus the neural system of higher animals performs three basic functions:
(i) Receiving sensory input from internal and external environment by sensory nerves to the CNS,
(ii) Processing the input information, in the CNS and
(iii) Responding to the stimuli transmitting motor commands from the CNS to determine the response of the body parts or cells.
The neural or nervous system is present in most of multicellular animals. It is very simple in lower invertebrates. Sponges do not have neurons. In Hydra all neurons are similar and joined with one another to form a nerve net forming “primitive nervous system”. Planaria has two nerve cords (bundles of nerve fibres) that join to form a rudimentary brain.
The earthworm has more evolved nervous system consisting of well developed ventral nerve cord, paired segmental ganglia and segmental nerves. Insects have well better organized nervous system, where a brain is present along with a number of ganglia and nerves. The vertebrates have more developed neural system as compared to invertebrates.
The brain is most complex and advanced in primates, particularly in human beings. This complexity of the neural system has increased during the course of evolution. It is due to the development of complex organs and systems in animals.
Thus neural system (previously called nervous system) performs two functions:
(i) Co-ordination and
(ii) Integration.
It involves control and coordination of various body functions through neurons. The neural system and the endocrine system jointly coordinate and integrate functions of various body parts to maintain normal physiology. The neural system provides an organized network of nerve fibres which connect various organs for quick neural coordination. The endocrine system provides chemical integration through hormones.
