Hormones a. are produced by exocrine glands, b. are carried to all parts of the body in blood, c. remain at constant concentration in the blood, d. affect only non-hormone-producing organs.

Video transcript

Welcome back. Let's look at our next problem. It says a hormone is a chemical messenger that is produced by specialized cells within the endocrine organs. It is carried to all parts of the body via blood and affects the target organs by a binding to specific receptors on the surface or inside the target cells. B attaching to the target organ and physically altering its structure. C killing off specific cells within the target orum or D stimulating an immune response in the body. Well, when we think about hormones, we should think about receptors along with them all the time. That's one of the things in which they have their targeted actions. So rather than doing all sorts of things all over the place, they have receptors particular to that hormone in the target organs or target tissues. When they bind to those receptors, they trigger a biochemical cascade or a series of reactions that ultimately causes a physiological effect. So choice A will be the answer we're looking for but just to be certain, we'll just look through our other answer choices and make sure nothing else seems like a better answer. Choice B says attaching to the target organ and physically altering its structure. But this is not how hormones work. They attach to receptors and they don't generally physically alter the structure of the organ. Again, they cause trigger these reactions that eventually carry out the physiological response. So choice B is not going to be your correct answer. Choice C killing off specific cells within the target organ. Um That's not to say that cell death would never be a result of the action of a hormone. But this is not the primary way that hormones act in general, their primary purpose is regulation of cellular activity, not killing off cells. So choice C is not going to be our correct answer. And then finally, choice D stimulating an immune response in the body. Uh some immune cells do respond to certain organs or certain, excuse me, certain hormones, for example, stress hormones can cause an effect on the immune system. But again, this is not the primary purpose or result of the action of hormones in the body. So, in general, they regulate physiological processes all over the body and in all different body systems, that's why choice D is not our best answer. So again, the hormones uh affect the target organs after they're carried throughout the body by a binding to specific receptors on the surface or inside their target cells. See you in the next video.