Development of the Nervous System
The
nervous system, derived from ectoderm, begins with embryonic disk formation.
The neural tube develops bulges, bends, and crevices that form mature brain
structures and ventricles. Three major bulges appear by approximately day 28 of
gestation: the forebrain (prosencephalon), midbrain (mesencephalon), and
hindbrain (rhombencephalon). At approximately day 36, the posterior (caudal)
portion of the forebrain develops into the diencephalon; the anterior part
develops into the telencephalon (eventually cerebral hemispheres). The cerebral
cortex has a specific outline by 6 months but develops sulci and
gyri only in the 3 months before birth. The developing brain is
affected, especially in the first trimester, to injuries caused by various
chemicals such as drugs. Various neurotransmitters and growth hormones play
critical roles in development of normal CNS function and restoration of
function after injury. Efforts aimed to identify these substances and design
drugs that will facilitate or enhance their actions are ongoing.
