This article, which forms part of the life sciences series and is the first of three articles on the nervous system, explores the major divisions of the nervous system and their functions. The basic structure of a nerve cell is described, and generation and conduction of nerve impulses is discussed. Blood supply to the brain is also covered. The second article will examine the central nervous system (CNS) in greater detail, including protection of the CNS, and the structure and function of the cerebral cortex and cerebellum. The third article will examine the peripheral nervous system and the autonomic nervous system, and provides an overview of some of the disorders of the nervous system.