Central nervous system

Mediates behaviour. Nerves in the CNS are called tracts. Information toward the CNS is called afferent, information leaving the CNS is called efferent.

Development
The development of the brain can be read in the article about the brain.
 * A zygote is first a single cell.
 * After 15 days of division, it's formed several sheets of cells with a raised area called the embryonic disc.
 * After 21 days the neural plate (primitive neural tissue) is formed.
 * The neural plate folds to form a groove, and then curls into a neural tube. This neural tube is lined with neural stem cells (see below).
 * By 7 weeks, the embryo looks like a person.
 * By 60 days, exposure or absence to testosterone leads to sexual dimorphism.

Neurons and glia
Neural stem cells line the ventricles. They produce progenitor cells, which can divide and produce neuroblasts and glioblasts. These, in turn, can turn into neurons and glia.