 |  Biology, 6/e Author Dr. George B. Johnson,
Washington University
Author Dr. Peter H. Raven,
Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer,
Carleton College
Contributor Dr. Jonathan Losos,
Washington University
The Endocrine System
Answers to Review Questions|
Chapter 56 (p. 1146)
1. A hormone is a regulating chemical made at one place in the body that exerts influence at another part. Hormones are manufactured in ductless glands and travel to their target organs or cells through the bloodstream. Only certain organs or tissues respond because only they have the proper receptors.
2. Hormones can affect cells at a great distance from the endocrine gland that secretes them. In paracrine regulation, only an immediately local area is affected.
3. When epinephrine binds to b-adrenergic receptors on the surface of the target cell, G proteins activate adenylyl cyclase, which catalyzes the formation of cAMP from ATP. cAMP then binds to and activates protein kinase-A, which can phosphorylate any number of important cellular proteins and effect a change in the cell.
4. The secretions of the posterior pituitary gland are actually produced by the hypothalamus.
5. The hormones of the anterior pituitary are called tropic hormones because they stimulate other endocrine glands to secrete their hormones, thereby creating a response.
6. Most of the hormones secreted by the hypothalamus are releasing hormones; they initiate the production of specific anterior pituitary hormones. These include TRH (TSH), CRH (ACTH), GnRH (LH, FSH) and GHRH (GH). A few others inhibit the release of pituitary hormones like somatostatin (GH), PIF (PRL) and MIH (MSH).
7. The adrenal cortex produces cortisol and aldosterone, which homeostatically regulate blood glucose and sodium ion levels, respectively. Low blood glucose levels stimulate the secretion of cortisol.
8. Insulin is produced when glucose levels become elevated, and it mediates the uptake of glucose by the liver cells, stimulating formation of glycogen in the liver.
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2002 McGraw-Hill Higher Education