Chapter 56

Summary		Questions		Media Resources
56.1 Regulation is often accomplished by chemical messengers.
• Endocrine glands secrete hormones into the blood, which are then transported to target cells. • Hormones may be lipophilic, such as the steroid hormones and thyroxine, or hydrophilic, such as amine, polypeptide, and glycoprotein hormones. • Prostaglandins and other paracrine regulatory molecules are produced by one cell type and regulate different cells within the same organ.		1.  What is the definition of a hormone? How do hormones reach their target cells? Why are only certain cells capable of being target cells for a particular hormone? 2.  How do hormones and paracrine regulators differ from one another?		• Endocrine System • Human Endocrine System
56.2 Lipophilic and polar hormones regulate their target cells by different means.
• Lipid-soluble hormones enter their target cells, bind to intracellular receptor proteins, and the complex then binds to hormone response elements on the DNA, activating specific genes. • Polar hormones do not enter their target cells, but instead bind to receptor proteins on the cell membrane and activate second-messenger systems or control ion channels.		3.  How does epinephrine result in the production of cAMP in its target cells? How does cAMP bring about specific changes inside target cells?		•Peptide Hormone Action •Steroid Hormones •Peptide Hormones •Steroid Hormone Action •Thyroxine Action •Cyclic AMP
56.3 The hypothalamus controls the secretions of the pituitary gland.
• Axons from neurons in the hypothalamus enter the posterior pituitary, carrying ADH and oxytocin; the posterior pituitary stores these hormones and secretes them in response to neural activity. • The anterior pituitary produces and secretes a variety of hormones, many of which control other endocrine glands; the anterior pituitary, however, is itself controlled by the hypothalamus via releasing and inhibiting hormones secreted by the hypothalamus.		4.  Where are hormones secreted by the posterior pituitary gland actually produced? 5.  Why are the hormones of the anterior pituitary gland called tropic hormones? 6.  How does the hypothalamus regulate the secretion of the anterior pituitary?		•Endocrine System Regulation •Hypothalamus •Human System Overview •Pituitary Control by Hypothalamus •Negative Feedback Inhibition
56.4 Endocrine glands secrete hormones that regulate many body functions.
• The thyroid secretes thyroxine and triiodothyronine, which set the basal metabolic rate by stimulating the rate of cell respiration in most cells of the body. • The adrenal cortex secretes cortisol, which regulates glucose balance, and aldosterone, which regulates Na+ and K+ balance. • The b cells of the islets of Langerhans in the pancreas secrete insulin, which lowers the blood glucose; glucagon, secreted by the a cells, raises the blood glucose level.		7.  What hormones are produced by the adrenal cortex? What functions do these hormones serve? What stimulates the secretion of these hormones? 8.  What pancreatic hormone is produced when the body's blood glucose level becomes elevated?		•Parathyroid Hormone •Glucose Regulation •Introduction to the Endocrine System •Endocrine Glands •Endocrine System • Type Two Diabetes •Hormonal Control of Metamorphosis

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