title: The pineal organ (first of two parts).
mesh_terms: D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism; D000818:Animals; D002940:Circadian Rhythm; D003624:Darkness; D006801:Humans; D008027:Light; D008029:Lighting; D008550:Melatonin / Q000096:biosynthesis* / Q000502:physiology; D008954:Models, Biological; D010870:Pineal Gland / Q000201:enzymology / Q000502:physiology*; D051381:Rats; D013564:Sympathetic Nervous System / Q000502:physiology
chemical_list: D000121:Acetylserotonin O-Methyltransferase; D008550:Melatonin