1. Hormones and the Endocrine System Chapter 45

2. ENDOCRINE SYSTEM Endocrine system – chemical signaling by hormones Endocrine glands – hormone secreting organs Hormones – chemical signals that are secreted into body fluids (usually blood) and communicate regulatory messages throughout body –Regulate growth, development, reproduction, metabolism, and behavior

3. Figure 45.2 Hormonal regulation of insect development (Layer 3)

6. CHEMICAL SIGNALING Reception – a receptor detects a signal (usually signal binds to receptor) Transduction – binding of signal to receptor changes receptor’s shape which initiates chemical changes (often several steps) Response – final transduced signal triggers a specific cell response

7. Figure 45.3 Mechanisms of chemical signaling: a review

9. Different cells will have different receptors. This means that one hormone only affects cells that have receptors for that specific hormone. However, different cells may have different receptors for same hormone which can then cause different affects.

10. Figure 45.4 One chemical signal, different effects

11. HUMAN ENDOCRINE GLANDS Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary or testis (gonads)

12. Figure 45.5 Human endocrine glands surveyed in this chapter

13. PANCREAS Secretes insulin and glucagon from the islets of Langerhans in pancreas Insulin and glucagon are antagonistic hormones. Metabolic balance requires a minimum of 90 mg glucose/100 ml blood. When blood glucose rises over 90mg/100ml: –Insulin lowers blood glucose by stimulating body cells to take in glucose. –Insulin also slows glycogen breakdown in liver.

14. Before blood glucose reaches 90mg/100ml: –Glucagon signals liver cells to break down glycogen into glucose and release to blood –Signals liver cells to convert amino acids and glycerol into glucose and release to blood

15. Figure 45.12 Glucose homeostasis maintained by insulin and glucagon

16. Diabetes Mellitus Caused by a deficiency of insulin or loss of response in target tissues Result is high blood glucose levels – so high that a diabetic’s urine contains glucose More glucose in urine means more water needed in urine = thirst Cells don’t get the glucose they need so they break down fat instead, which forms harmful, acidic metabolites.

17. Type I diabetes mellitus –Insulin dependent –Autoimmune disease where immune system attacks pancreas (  cells) and cannot make insulin –“Juvenile” (adults too) –Inheritance may play a minor role –Potentially caused by infections

18. Type II diabetes mellitus –Non-insulin dependent –Often inherited (although related to poor diets and lack of exercise) –Either insulin deficient or lack of response in target cells –Accounts for 90% of all diabetics –Gastric by-pass surgery (duodenum and jejunum removal) ends diabetes in most obese patients Gestational diabetes – happens to pregnant women (may be from hormones from placenta causing insulin resistance in mom)

19. Figure 45.14 Stress and the adrenal gland

20. SHORT TERM STRESS Stressful stimuli cause hypothalamus to activate adrenal gland via a nerve to secrete epinephrine (adrenaline) and norepinephrine (noradrenaline). Multiple effects: –Glycogen broken down to glucose; increases blood glucose –Increased blood pressure and stroke volume –Increased breathing rate (dilates bronchioles)

21. –Increased metabolic rate –Change in blood flow patterns leading to decreased digestion and kidney activity –Increase rate of oxygen delivery to cells (used to stimulate heart)

22. Figure 45.12 The synthesis of catecholamine hormones

23. LONG TERM STRESS Hypothalamus secretes a releasing hormone that activates the anterior pituitary to release ACTH (adrenocorticotropic hormone) When ACTH reaches the adrenal gland via blood it stimulates the gland to secrete corticosteroids. Two main types of corticosteroids –Glucocorticoids (ex. Cortisol) –Mineralcorticoids (ex. Aldosterone)

24. Glucocorticoids –Promotes glucose synthesis from noncarbs like proteins – used for fuel –Break down skeletal muscle for protein source –Suppress some parts of immune system (ex. Anti-inflammatory) Mineralcorticoids –Aldosterone stimulates kidneys to reabsorb water and sodium so blood volume and therefore blood pressure increases