Give a brief account of the functional components of the vertebrate nervous system.

The extremely complex nervous system of vertebrates is divided into two main divisions – the central nervous system (CNS), composed of brain and spinal cord is site of information processing; and peripheral nervous system (PNS), composed of all the nerves of the body outside the brain and spinal cord. The peripheral nerves are divided into two groups: sensory (afferent) nerves, which transmit impulses from receptors to the central nervous system; and motor (efferent) nerves, which carry impulses from the central nervous system to voluntary and involuntary nervous systems. The voluntary or somatic nervous system relays commands to the skeletal muscles, and the involuntary or visceral or autonomic nervous system stimulate smooth and cardiac muscles and glands of the body. The nerves of the autonomic system divide into: sympathetic nervous system, responsible for the ‘light or flight” response; and the parasympathetic nervous system which functions during relaxation. Fig.2.10

A summery of main components of nervous system is as under

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