Describe neurulation and relate the components of a fully developed nervous system to the neural tube and neural crest.

Neurulation is termed as the folding process within which is invertebrates embryos. It includes the transformation of the neural plate into the neural tube. At this transformation of the neural plate into the neural tube. At this stage, the embryo is known as neurula. 
The process starts when notochord induces the formation of the central nervous system and this is by signaling the ectoderm germ layer which is above and it forms flat and thick neural plate.
The work of neural tube and then later differentiates to the brain and spinal chord which then forms central nervous system.
Neural tube portions forms by two different processes. for example secondary neurulation and primary neurulation.
Secondary neurulation the tube forms by hollowing out of the interior of the solid precursor
In primary neurulation, the neural plates crease inward until when the edges come into fuse and contact