Chapter 1 provides an organizational overview of the nervous system as well as the structures and functions association with each of the major subdivisions. This chapter also includes information concerning brain development, the process of neurulation, and factors contributing to prenatal brain growth and maturation, including cell migration, differentiation, aggregation, neurogenesis, gliogenesis, synaptogenesis, neurotrophins, and apoptosis. Mechanisms contributing to neuroplasticity are reviewed in relation to traumatic brain injury (TBI), stroke, developmental conditions, amputation and phantom limb, and deprivation and enrichment studies. Lastly, protection and metabolic needs of the brain, as well as information concerning sex differences in brain morphology and function, are reviewed.