RT Book, Section A1 Hoyer, Patricia B. A1 Flaws, Jodi A. A2 Klaassen, Curtis D. SR Print(0) ID 1158500922 T1 Toxic Responses of the Endocrine System T2 Casarett & Doull’s Toxicology: The Basic Science of Poisons, 9th edition YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9781259863745 LK accessbiomedicalscience.mhmedical.com/content.aspx?aid=1158500922 RD 2024/03/29 AB Higher animals, including humans, have developed the ability to regulate their internal environment, independent of wide fluctuations in external factors, in the form of endocrine systems. An endocrine system consists of (1) an endocrine gland that secretes a hormone, (2) the hormone itself, and (3) a target tissue that responds to the hormone. The classical definition of a hormone is “a chemical substance produced by a ductless endocrine gland and secreted into the blood, which carries it to a specific target organ to produce an effect.” In addition to the humoral communication regulated by endocrine systems, the nervous system also regulates overall bodily functions. The two systems are intimately interconnected and normally work in close concert. One direct point at which the two systems interface involves “neuroendocrine” cells, which are special types of neurons capable of secreting humoral substances (hormones) in response to synaptic input (neurotransmitters).