The central nervous system includes the brain and spinal cord.
The attraction that holds two covalently bonded atoms together is called covalent bond
This interaction process is an example of epigenesis.
Epigenesis is processes in which living organisms such as plants, animals and fungi grow from a seed, egg or spore through a series of steps in which cells differentiate and organs form. The theory of epigenesis which was created by C. F. Wolff claimed that structures emerge during development that are not initially formed.