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CHAPTER 25 Hormones Hormones: An Overview • The endocrine system – Is the body’s main system for internal chemical regulation. • Hormones – Are regulatory chemicals that affect specific sites in the body. – Are made and secreted by endocrine glands. Hormone Secretion from an Endocrine Cell •A cell within the endocrine gland secretes hormone molecules •The hormone is carried by the circulatory system to all cells of the body •The hormone only affects target cells Hormones Trigger Changes in Target Cells • There are two general mechanisms by which hormones trigger changes in target cells. • In the first mechanism, – Hormones bring about changes without ever entering their target cells. – These hormones are protein hormones – Example: insulin Hormones Trigger Changes in Target Cells • In the second mechanism, – Hormones trigger changes by binding to receptors inside the cell. – These are lipid-soluble hormones – Ex: sex hormones The Human Endocrine System • The human endocrine system consists of about a dozen major glands. • The major endocrine glands in humans The Pancreas • The pancreas – Produces two hormones that play important roles in managing the body’s energy supplies. • Insulin and glucagon – Help maintain a homeostatic balance of blood glucose and stored glucose. – Are antagonists. • Control of blood glucose and stored glucose is carried out by negative feedback. • Diabetes mellitus – Is a hormonal disease in which body cells are unable to absorb glucose. – Includes type 1, or insulin-dependent diabetes, and type 2, or noninsulin-dependent diabetes. – Can be treated.
