Answer:
Step-by-step explanation:
Histamine and nitric oxide are not considered true hormones because they do not meet all of the criteria for hormones.
Criteria for hormones:
Hormones are secreted by endocrine glands.
Hormones are transported through the bloodstream to their target cells.
Hormones bind to specific receptors on their target cells and elicit a response.
Hormones are regulated by feedback mechanisms.
Histamine and nitric oxide are both produced by a variety of cells throughout the body, not just by specialized endocrine glands. Additionally, they are both locally acting signaling molecules, meaning that they act on cells in their immediate vicinity, rather than being transported through the bloodstream to distant target cells.