endocrine system.ppt

1、Endocrine system,1.Introduction,The endocrine system is made up of glands that produce and secrete hormones. These hormones regulate the bodys growth, metabolism (the physical and chemical processes of the body), and sexual development and function.,2.Hormone,Hormone is a chemical released by a cell

2、 in one part of the body, that sends out messages that affect cells in other parts of the organism. Hormones are produced in extremely small amounts and are highly potent. Chemically, hormones fall into two categories: steroid hormone, made of lipids, and hormones made of amino acids, which include

3、proteins and proteinlike compounds.,Types of hormone action,Endocrine action: the hormone is released into blood and act on distant target cells. Paracrine action: the hormone acts locally by diffusing from its source to target cells in the neighborhood. Autocrine action: the hormone acts on the sam

4、e cell that produced it.,Receptor,Most hormones are directly released into blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are called target cells. Target cell responds to a hormone because it bears specific recept

5、ors on their membrane to which the hormone attached, enabling it to act on the cells.,Cell surface receptors have regions that contribute to three basic domains: Extracellular domains: Some of the residues exposed to the outside of the cell interact with and bind the hormone Transmembrane domains: H

6、ydrophobic stretches of amino acids in the lipid bilayer and serve to anchor the receptor in the membrane. Cytoplasmic or intracellular domains: Tails or loops of the receptor that are within the cytoplasm ,react to hormone binding by interacting in some way with other molecules, leading to generati

7、on of second messengers.,Binding of hormone to receptor initiates a series of events which leads to generation of so-called second messengers within the cell (the hormone is the first messenger). The second messengers then trigger a series of molecular interactions that alter the physiologic state o

8、f the cell.,Agonists and Antagonists,Agonists are molecules that bind the receptor and induce all the post-receptor events that lead to a biologic effect. In other words, they act like the normal hormone, although perhaps more or less potently. Antagonists are molecules that bind the receptor and bl

9、ock binding of the agonist, but fail to trigger intracellular signalling events. Hormone antagonists are widely used as drugs.,estrogen antagonist and breast cancer,estrogens are a group of steroid compounds and mainly produced by ovary, functioning as the primary female sex hormone. About 80% of br

10、east cancers rely on supplies of the hormone estrogen to grow. Estrogen antagonist can block proliferative effects of estrogen on breast cancer cells.,3.Endocrine gland,A gland is a group of cells that produces and secretes, or gives off, chemicals. The major glands that make up the human endocrine

11、system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, pancreas and the reproductive glands.,Thyroid required for normal growth calcitonin： acts to reduce blood calcium parathyroid hormone (parathormone,PTH): acts to increase blood calcium,goiter (thyromegaly): swellin

12、g in the thyroid gland, which can lead to a swelling of the neck or larynx hyperthyroidism: overproduction and thus an excess of circulating free thyroid hormones hypothyroidism: insufficient production of thyroid hormone,Pancreas,insulin: causes cells in the liver, muscle, and fat tissue to take up

13、 glucose from the blood, storing it as glycogen in the liver and muscle, and stopping use of fat as an energy source. glucagon: causes the liver to convert stored glycogen into glucose and release it into the bloodstream, raising blood glucose levels and ultimately preventing the development of hypo

14、glycemia,Diabetes The most common endocrine disorder, and a serious public health problem, a failure of the body cells to use glucose effectively. The excess glucose accumulates in the blood, causing hyperglycemia. Increased urination (polyuria) marks the effort to eliminate the excess glucose in th

15、e urine, a condition termed glycosuria. The result is dehydration and excessive thirst (polydipsia). There is also weakness, weight loss, and extreme hunger (polyphagia).,Pituitary,GH (growth hormone),somatotropin: promotes growth of all body tissues thyroid-stimulating hormone: stimulates thyroid g

16、land to produce thyroid hormones vasopressin: promotes reabsorption of water in kidney tubules; stimulates smooth muscle tissue of blood vessels to constrict prolactin: stimulate secretion of milk by mammary glands,acromegaly: Overgrowth of bone and soft tissue, especially in the hands, feet, and fa

17、ce, caused by an excess of growth hormone in an adult. gigantism: excessive growth and height significantly above average,Adrenal gland,epinephrine (adrenaline) and norepinephrine (noradrenaline): active in response to stress; increases respiration, blood pressure, and heart rate hydrocortisone(氢化可的

18、松): aids in metabolism of carbohydrates, proteins, and fats; active during stress,Although the endocrine glands are the bodys main hormone producers, some non-endocrine organs such as the brain, heart, lungs, kidneys, liver, thymus, skin, and placenta also produce and release hormones.,Other hormones,gastrin: a hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility. It is released by G cells in the stomach and duodenum. cholecystokinin: stimulates secreti