The Endocrine System

1. The Endocrine System

2. Introduction • Second messenger system of the body • Hormones control several major processes • Reproduction • Growth and development • Mobilization of body defenses • Maintenance of much of homeostasis • Regulation of metabolism

3. Introduction • Endocrine glands are “ductless”. They release hormones directly into the blood or lymph

5. Hormones • Cells secrete hormones into extracellular fluids • Blood transfers hormones to target sites • These hormones regulate the activity of other cells • Steroid Hormones- derived from cholesterol. They are sex hormones and adrenal cortex hormones Ex. Estrogen, testosterone. Cortisol. • Nonsteroid Hormones- amines, proteins, peptides, glycoproteins, most hormones Ex. OT, FSH, TSH

7. Major Glands

8. Pituitary Gland Size of a grape • Hangs by a stalk from the hypothalamus • Protected by the sphenoid bone • Has two functional lobes • Anterior pituitary – glandular tissue • Posterior pituitary – nervous tissue • Technically not an endocrine gland but a storage area for hormones produced by the hypothalamus

9. Anterior Pituitary Hormones • Growth Hormone (GH)- stimulates increase in size and rate of body cells, enhances movement of amino acids through membranes, promotes growth of long bones, • Prolactin (PRL)- sustains milk production after birth, amplifies effect of LH in males, • Thyroid Stimulating Hormone (TSH)- controls secretions of hormones from the thyroid gland,

10. Cont…….. • Adrenocorticotropic Hormone (ACTH)- controls secretions of some hormones of adrenal cortex, • Follicle-Stimulating Hormone (FSH)- stimulates development of egg-containing follicles in ovaries, stimulates follicular cells to secrete estrogen, stimulates production of sperm cells • Luteinizing Hormone (LH)- promotes secretions of sex hormones, stimulates release of egg from ovary, promotes growth of long bones

11. Posterior Pituitary Hormones • Antidiuretic Hormone (ADH)- causes kidneys to reduce water excretion, in high concentration, raises blood pressure, controlled by hypothalamus in response to changes in blood water concentration and blood volume • Oxytocin (OT)- stimulates uterine contractions, stimulates mammary glands to release milk, controlled by hypothalamus in response to stretch in uterine and vaginal walls and stimulation of breasts

12. Overview

13. Thyroid Hormones • Thyroxine (T4) and Triiodothyronine (T3)- increases rate of energy release from carbohydrates, increases rate of protein synthesis, accelerates growth, stimulates activity in the nervous system, controlled by TSH • Calcitonin-lowers blood calcium and phosphate ion concentrations by inhibiting release of calcium and phosphate from bones, increases rate at which calcium and phosphate are deposited in bones

14. Thyroid Disorders • General Hyperthyroidism high metabolic rate, hyperactivity, weight loss, protruding eyes • Cretinism- hypothyroidism in infants, leads to small stature and mental retardation • Myxedema- adult hypothyroidism, low metabolic rate, sluggishness

15. Parathyroid Hormone • PTH-increases blood calcium levels, decreases blood phosphate levels, stimulates bone resorption by osteoclasts, inhibits osteoblasts, stimulates kidneys to retain calcium and excrete phosphate, promotes calcium absorption into intestine • Disorders: Hyperparathyroidism- caused by tumor, fatigue, muscular weakness, altered mental functions, bone weakening. Hypoparathyroidism- caused by injury or removal of gland, muscle cramps, seizures, low blood calcium levels

16. Adrenal Hormones • Epinephrine and Norepinephrine- come from the medulla of the adrenal gland release controlled by sympathetic nervous system, increases heart rate and blood pressure, dilates respiratory airways, promotes breakdown of glycogen, activates reticular formation, increases metabolic rates • Cortex Hormones: Aldosterone-increases blood volume and pressure by promoting conservation of sodium ions and water. Cortisol- decreases protein synthesis, increases fatty acid release, stimulates glucose synthesis from noncarbohydrates. Adrenal androgens- supplement sex hormones from the gonads, may be converted to estrogen

17. Pancreatic Hormones • Glucagon-stimulates liver to break down glycogen, stimulates liver to convert noncarbohydrates into glucose, stimulates break down of fats, controlled by blood glucose concentrations • Insulin-promotes formation of glycogen from glucose, inhibits conversion of noncarbohydrates into glucose, enhances movement of glucose into adipose and muscle cells, decreases blood glucose concentrations, promotes transport of amino acids, enhances synthesis of proteins and fats, controlled by blood glucose concentrations

18. Others • Pineal Gland- secretes melatonin, regulates circadian rhythms, may control onset of puberty, helps regulate female reproductive cycles • Thymus Gland- secretes thymosins, promotes development of certain lymphocytes (T-cells) • Reproductive Glands-ovaries secrete estrogen and progesterone: develops and maintains female secondary sex characteristics and uterine lining growth,testes secrete testosterone: develops and maintains male secondary sex characteristics and sperm formation,placenta secretes estrogen, progesterone, and gonadotropins

19. Life’s little Curves • endocrine glands shrink • GH levels even out, muscular strength decreases • ADH levels increase due to slow break down • calcitonin levels decrease • PTH increases, osteoporosis risk increases • insulin resistance may develop • changes in melatonin secretion affect the body clock • thymosin production declines increasing risk of infections

20. How are they Released

22. References • Jack Brown M.S. Biology • Shier,David, Jackie Butler, Ricki Lewis: Hole’s Human Anatomy and Physiology 10th edition: 2004: McGraw-Hill • Marieb, Elaine: Essentials of Human Anatomy and Physiology 7th edition. 2003: Pearson Education Inc: Benjamin Cummings pub. • Microsoft Encarta Encyclopedia 2004