Q. How does the embryo turn from gastrula into neurula? How is the neural tube formed? What is the embryonic origin of the nervous system in vertebrates?

The neurula stage is characterized by the appearance of the neural tube along the dorsal region of the embryo and the growth of mesoderm in that region induces the differentiation of ectodermal cells just above and these cells then differentiate forming the neural tube so the origin of the nervous system is the ectoderm the same germ layer that gives birth to the skin.