Chapter 15

1. Chapter 15 Endocrine System

2. Points to Ponder • What is the endocrine system? • Compare and contrast exocrine and endocrine glands. • What are steroid and peptide hormones? • Name the major glands and their functions in the endocrine system. • What is diabetes (Type 1 and 2) and how might you prevent Type 1? • How do the endocrine nervous systems work with the rest of the systems in the body to maintain homeostasis?

3. 15.1 Endocrine glands Endocrine system • Mostly comprised of glands • Secretes hormones that move through the bloodstream to target cells • Results in a slow but a prolonged response

4. 15.1 Endocrine glands Endocrine system

5. 15.1 Endocrine glands What is a target cell?

6. 15.1 Endocrine glands Exocrine vs. endocrine glands • Exocrine glands secrete their products into ducts that carry these products to other organs or outside the body • Endocrine glands secrete their products directly into the bloodstream

7. 15.1 Endocrine glands What are hormones? • Hormones are chemical signals that promotes communication between cells, body parts and even individuals • Hormones: • Prostaglandins: local hormones affect neighboring cells and thus are not carried in the bloodstream • Pheromones: chemical signals that influence the behavior of other individuals • Peptide hormones: bind to a receptor in the plasma membrane causing the formation of cAMP which activates a cascade of enzymes • Steroid hormones: lipids that enter a cell and affect gene activity and thus protein synthesis

8. 15.1 Endocrine glands Action of peptide hormones

9. 15.1 Endocrine glands Action of steroid hormones

10. 15.2 Hypothalamus and pituitary gland Major glands of the endocrine system • Hypothalamus • Posterior pituitary gland • Anterior pituitary gland • Thyroid gland • Parathyroid glands • Adrenal glands • Pancreas • Testes • Ovaries • Thymus gland • Pineal gland

11. 15.2 Hypothalamus and pituitary gland 1. Hypothalamus • Regulates internal environment through the autonomic nervous system • Helps control heartbeat • Helps control body temperature • Helps control water balance • Controls glandular secretions

12. 15.2 Hypothalamus and pituitary gland 2. Posterior pituitary gland • Stores antidiuretic hormone (ADH) and oxytocin that are produced by the hypothalamus • ADH: regulates water balance by reabsorbing water into the bloodstream • Oxytocin: causes uterine contractions during childbirth and allow milk to be released during nursing

13. 15.2 Hypothalamus and pituitary gland 3. Anterior pituitary gland • Controlled by hypothalamic-releasing and hypothalalmic-inhibiting hormones • Hormones produced by the anterior pituitary: • Thyroid-stimulating hormone (TSH): stimulates the thyroid to produce thyroid hormones • Adrenocorticotropic hormone (ACTH): stimulates the adrenal cortex to produce cortisol • Gonadotropic hormones: stimulate gonads to produce sex cells and hormones • Prolactin (PRL): stimulates mammary glands to develop and produce milk only after childbirth • Melanocyte-stimulating hormone (MSH): causes skin cells to produce melanin • Growth hormone (GH): promotes skeletal and muscular growth

14. 15.2 Hypothalamus and pituitary gland The hypothalamus and pituitary

15. 15.2 Hypothalamus and pituitary gland What happens when the body produces too much or too little GH? • Pituitary dwarfism – too little GH is produced during childhood that results in small stature • Giantism – too much GH is produced during childhood that results in poor health • Acromegaly – overproduction of GH as an adult that results in larger than normal feet, hands, and face

16. 15.2 Hypothalamus and pituitary gland What happens when GH is produced in improper results during childhood?

17. 15.2 Hypothalamus and pituitary gland What happens when GH is produced in high amounts during adulthood?

18. 15.3 Thyroid and parathyroid glands 4. Thyroid gland • A large gland located below the larynx • Iodine is needed in the diet to allow the thyroid gland to produce its hormones • It produces: • Thyroid hormone (TH): regulates metabolism • Calcitonin: helps lower blood Ca2+ levels by stimulating the deposition of calcium in the bones

19. 15.3 Thyroid and parathyroid glands Thyroid abnormalities • Simple goiter – thyroid enlarges due to lack of iodine in the diet • Hypothyroidism – low blood levels of thyroid hormones • Congenital hypothyroidism: thyroid does not develop properly and is characterized in a short, stocky person that may be mentally retarded • Myxedema: hypothyroidism in adults characterized by lethargy, weight gain, loss of hair, cold intolerant and thick, puffy skin • Hyperthyroidism – excess thyroid hormones in the blood • Exophthalimic goiter: such as seen in Graves' disease and is characterized by enlargement of the thyroid gland, protrusion of the eyes, hyperactive and suffers from insomnia • Thyroid tumor: can also cause hyperthyroidism

20. 15.3 Thyroid and parathyroid glands Thyroid abnormalities

21. 15.3 Thyroid and parathyroid glands 5. Parathyroid glands • Small glands embedded in the surface of the thyroid gland • Produces parathyroid hormone (PTH): • causes blood Ca2+ level to increase by promoting osteoclast activity • Promotes reabsorption of Ca2+ by the kidneys

22. 15.3 Thyroid and parathyroid glands Regulation of blood calcium

23. 15.4 Adrenal glands 6. Adrenal glands • Glands that sit on top of the kidneys • 2 parts of each gland • Adrenal medulla: controlled by the nervous system • Adrenal cortex: portions are controlled by ACTH from the anterior pituitary

24. 15.4 Adrenal glands Adrenal medulla • Inner portion of the adrenal glands • Hypothalamus initiates stimulation of hormone secretion in the adrenal medulla • Produces: hormones that allow a short-term response to stress (“fight or flight” response) • Epinephrine (adrenaline) • Norepinephrine

25. 15.4 Adrenal glands Adrenal cortex • Outer portion of the adrenal glands • Produces hormones that provide a long-term response to stress • 2 major types of hormones: • Mineralocorticoids : • regulate salt and water balance • e.g. aldosterone (targets the kidney) • Glucocorticoids: • regulate carbohydrate, protein and fat metabolism • Suppress the body’s inflammatory response • e.g. cortisol and cortisone

26. 15.4 Adrenal glands Summary of the adrenal glands

27. 15.4 Adrenal glands Adrenal glands can malfunction • Addison’s disease – hyposecretion of glucocorticoids by the adrenal cortex characterized by bronzing of the skin

28. 15.4 Adrenal glands Adrenal glands can malfunction • Cushing syndrome – hypersecretion of glucocorticoids by the adrenal cortex characterized by weight gain in the trunk of the body but not arms and legs

29. 15.5 Pancreas 7. Pancreas • Fish-shaped organ behind the stomach • Composed of 2 tissues: • Exocrine: produces and secretes digestive juices • Endocrine (islets of Langerhans): produces and secretes hormones • Insulin – secreted when blood glucose is high and stimulates uptake of glucose by cells (muscle and liver) • Glucagon – secreted when blood glucose is low and stimulates the breakdown of glycogen in the liver

30. 15.5 Pancreas Regulation of blood glucose

31. 15.5 Pancreas Health focus: What is diabetes? • Inability to control blood glucose levels • There are two types: Type 1 and Type 2 • 18 million people in the US have diabetes • General symptoms: • Frequent urination • Unusual hunger and/or thirst • Unexplained change in weight • Blurred vision • Sores that heal slowly or not at all • Excessive fatigue • Long-term effects are blindness, loss of limbs, nerve deterioration, kidney and cardiovascular disease

32. Type 1: Usually early-onset Autoimmune disorder that tends to run in families Pancreatic cells are attacked and cannot produce insulin Need insulin injections Type 2: Usually adult-onset and most common type Tends to occur in obese, sedentary people Cells do not respond to insulin Usually diet and exercise are important for controlling this and may even prevent this! 15.5 Pancreas Diabetes: Understanding the 2 types

33. 15.6 Other endocrine glands 8. Testes • Gonads found in males • Produce androgens (e.g. testosterone) • Stimulates growth of the penis and testes • Responsible for 2 male sex characteristics such as facial, underarm and pubic hair • Prompts the larynx and vocal cords to enlarge resulting in a lower voice • Promotes muscular strength

34. 15.6 Other endocrine glands 9. Ovaries • Gonads found in females • Produce estrogen and progesterone • Stimulates growth of the vagina and uterus • Responsible for secondary sex characteristics such as female body hair, fat distribution and breast development • Responsible for egg maturation • Regulates the uterine cycle

35. 15.6 Other endocrine glands Bioethical focus: You decide • Hormone replacement therapy (HTR) is often used to counteract some of the problems associated with menopause or to prevent an increased risk of osteoporosis • 2002 a study found that HTR: • May have risks that outweigh the benefits • Does not significantly increase the quality of life • Significantly increased the risk of breast cancer • May increase the risk of cardiovascular disease • Can prevent fractures as a result of osteoporosis

36. 15.6 Other endocrine glands 10. Thymus gland • Lies beneath the sternum • This gland is largest and most active during childhood • T lymphocytes mature here • Secretes hormones called thymosins that aid in differentiation of lymphocytes

37. Located in the brain Secretes melatonin that regulates the sleep/wake cycle (circadian rhythm) May also regulate sexual development 15.6 Other endocrine glands 11. Pineal gland

38. 15.6 Other endocrine glands Hormones from other tissues • Erythropoietin: secreted by the kidney to increase red blood cell production • Leptin:produced by fat cells and acts on the hypothalamus to give a feeling of being satiated • Prostaglandins: • A groups of potent chemicals that are not carried in the bloodstream but work locally on neighboring cells • Some cause smooth muscle contraction • Major impact on reproductive organs • Many other roles in the body • Aspirin and ibuprofen block the synthesis of these

39. 15.7 Homeostasis Homeostasis • The nervous and endocrine systems are important in maintaining homeostasis by: • The hypothalamus bridges regulatory functions of both systems • The nervous system is able to respond to changes in the external environment

40. 15.7 Homeostasis How the nervous and endocrine systems work with other body systems