Sorry for a certainly naive question. Some references (for example https://faculty.washington.edu/chudler/nsdivide.html) seem to to indicate that the hypothalamus is part of the Central Nervous System. Others (for example http://kidshealth.org/teen/your_body/body_basics/endocrine.html) place it in the Endrocrine System. I would have said it is part of both, but then I read the two systems are distinct. Could anyone explain me to which one it belongs and why?