Development of Nervous System - Overview of Brain Development

Overview of Brain Development

The nervous system is derived from the ectoderm, the outermost tissue layer, of the embryo. In the third week of development the neuroectoderm appears and forms the neural plate along the dorsal side of the embryo. This neural plate is the source of the majority of all neurons and glial cells in the mature human. A groove forms in the neural plate and, by week four of development, the neural plate wraps in on itself to make a hollow neural tube. Because this neural tube later gives rise to the brain and spinal cord any mutations at this stage in development can lead to lethal deformities like anencephaly or lifelong disabilities like spina bifida. The most anterior part of the neural tube is called the telencephalon, which expands rapidly due to cell proliferation, and eventually gives rise to the brain. Gradually some of the cells stop dividing and differentiate into neurons and glial cells, which are the main cellular components of the brain. The newly generated neurons migrate to different parts of the developing brain to self-organize into different brain structures. Once the neurons have reached their regional positions, they extend axons and dendrites, which allow them to communicate with other neurons via synapses. Synaptic communication between neurons leads to the establishment of functional neural circuits that mediate sensory and motor processing, and underlie behavior. The human brain does most of its development within the first 20 years of life.