The Endocrine system ch 45

1. The Endocrine system ch 45 The endocrine glands produce and secrete into the blood stream hormones that travel through the blood to stimulate cells with the matching receptor proteins.

2. Major Glands of Pituitary (the master gland, controlled by hypothalamus) • Thyroid • Parathyroid • Adrenal • Pancreas • Ovaries • Testes • Pineal

3. Hormones need a specific receptor on a specific cell type to cause a response. Hormones are “slow acting signals” relative to neurotransmitters, but both are involved in controlling homeostasis by cooperation between many different specialized cell types in a multicellular organism.

4. General process of hormone effects: Travel from gland through circulating blood; diffuse to cells in tissues, & bind to cells bearing matching receptor proteins. Receptor protein mediated Signal transduction cascades

5. Post-translational modifications allow membrane receptor proteins to convey signals. Via multi-protein signal transduction cascades that end with an effector protein (does the signalled task). Adding phosphate groups changes 3D shape (3° structure) of proteins in signal pathway. Kinasesare protein enzymes that add phosphate groups Shape change may switch protein from inactive to active Later, a phosphatase (phosphate group removing enzyme) returns protein to inactive shape.

6. Tyrosine kinasereceptor (autophosphorylatingdimers whose ligands activate kinase cascades)

7. G protein linked receptors activate G proteins (they get P’ated) which activate a kinase (PLC or PKC) which forms 2nd messengers activating cell responsese.g., ACh, neurotransmitter released by motor neurons at neuromuscular junctions binds PLC linked G protein receptor; Ca++ allows myosin to bind actin for muscle contraction.

8. Steroid hormone signal pathways (testosterone ,e.g.)

9. PKC stimulating Signal receptor G protein phosphorylated G protein (active) activate adenylcyclase make second messenger cAMP activate protein kinase A (PKA) activate effectors http://www.youtube.com/watch?v=DGkh7SGacgk e.g. many neurotransmitters work this way

11. Controls many body functions exerts control by releasing special chemical substances into the blood called hormones Hormones affect other endocrine glands or body systems Response depends on which 2nd messenger or signal cascades/effectors are activated Derives its name from the fact that various glands release hormones directly into the blood (endocrine glands), which in turn transports the hormones to target tissues The Endocrine System

12. Exocrine glands - transport their secretions to target tissues via ducts sweat glands, salivary glands, mammary glands, stomach, liver, Pancreas (these secretions are digestive enzymes or other nonhormone liquids Endocrine glands secrete into blood Most endocrine secretions are hormones The hypothalamus signals pituitary gland via neurosecretory cells that produce hormones signaling releasing hormone production in the pituitary The Endocrine System

13. Hypothalamus—brain structure connected via neurosecretory cells to pituitary gland Secretes releasing hormones that affect pituitary gland + regulate temperature, blood osmolality, & water balance (thirst, urine concentration)

14. Hypothalamus & control of blood pressure & blood osmolality via effects on the kidney

15. Metabolic rates too low, hypothalamus secretes thyroid hormone releasing hormone into the pituitaryThyroid stimulating hormonethyroidthyroxinsNegative feedback of this metabolism regulating pathway: sufficient thyroxinsuppression of either secretion from the hypothalamus OR the anterior pituitary.

16. Negative feedback control of Ca ion in blood: calcitonin & PTH are opposing hormones

17. Negative feedback of blood glucose concentrations: Insulin & glucagon have opposing actions.

18. Long term responses of stress are initiated by hypothalamuspituitaryACTH to blood adrenal cortexkidney (aldosterone, a mineral corticoid increases Na+ & water retention in kidney, raising blood pressure). Short term response to stress—fight or flight—initiated by hypothalamusmotor neurons of sp cordadrenal gland secreting epinephrine (adrenaline)act on targets like sympathetic neurons to prepare the body for emergencies.

19. Thyroid- produces hormones that control metabolism T3 & T4 thyroxin (thyroid hormone) and calcium (calcitonin) in blood. • Thyroid gland must have any source of iodine to make T3 & T4 • goiter- not enough iodine • hyperthyroidism too much TH • hypothyroidism too little TH

20. Adrenal glands • Located just above the kidney • Secretes many hormones including Epinephrine * Norepinephrine (*adrenaline, fight or flight response) Aldosterone—induce Na+ retention in distal tubule & water reabsorption higher blood V, lower urine V, higher Blood P

21. Diabetes Mellitus- • Cause- decreased secretion of insulin • Symptoms • Excessive thirst, excessive urination, hyperglycemia, slow healing of skin infections • Affects 21 million in US: 7% of population • Estimated 1/3 of people who have diabetes don’t know it • 225,000 die each year • 132 billion/year- 10% of our health care spending

22. And even more… luteinizing hormone (LH) prolactin Let’s go over these one at a time... anterior Pituitary Oxytocin (the natural form of pitocin) stimulates gravid uterus causes “let down” of milk from the breast. ADH (vasopressin) causes the kidney to retain water. The Endocrine System

23. Anterior Pituitary Primarily regulates other endocrine glands rarely a factor in endocrinological emergencies TSH stimulates the thyroid gland to release its hormones, thus  metabolic rate Anterior Pituitary… Growth hormone (GH)  glucose usage  consumption of fats as an energy source ACTH stimulates the adrenal cortex to release its hormones FSH & LH stimulates maturation & release of eggs from ovary. The Endocrine System

24. T3, T4 thyroxin or thyroid hormone: hypothalamus signals pituitary release of TSH. T3, T4 increase metabolism. Calcitonin, when released, lowers the amount of calcium in the blood. Inadequate levels of thyroid hormones = hypothyroidism, or Myxedema. Myxedema symptoms: Facial bloating weakness cold intolerance lethargy altered mental status oily skin and hair TX: replacement of thyroid hormone. The Endocrine System: thyroid gland

25. Increased thyroid hormone release causes hyperthyroidism, commonly called Graves’ disease. Signs and symptoms: insomnia, fatigue tachycardia hypertension heat intolerance weight loss Long term hyperthyroidism: Exopthalmos bulging of the eyeballs (picture Barbara Bush) In severe cases - a medical emergency called thyrotoxicosis can result. The Endocrine System

26. Parathyroid Glands small, pea-shaped glands, located in the neck near the thyroid usually 4 - number can vary regulate the level of calcium in the body produce parathyroid hormone -  level of calcium in blood Hypocalcemia can result if parathyroids are removed or destroyed. The Endocrine System

27. Pancreas a key gland located in the folds of the duodenum has both endocrine and exocrine functions secretes several key digestive enzymes Islets of Langerhans specialized tissues in which the endocrine functions of the pancreas occurs include 3 types of cells: alpha ( ) beta () each secretes an important hormone. The Endocrine System

28. Alpha () cells release glucagon, essential for controlling blood glucose levels. When blood glucose levels fall,  cells  the amount of glucagon in the blood . The surge of glucagon stimulates the liver to release glucose stores (from glycogen and additional storage sites). Also, glucagon stimulates the liver to manufacture glucose - gluconeogenesis. The Endocrine System

29. Beta Cells () release insulin (antagonistic to glucagon). Insulin  the rate at which various body cells take up glucose. Thus, insulin lowers the blood glucose level. Insulin is rapidly broken down by the liver and must be secreted constantly. The Endocrine System

30. Adrenal Glands 2 small glands that sit atop both kidneys. Each has 2 divisions, each with different functions. the Adrenal Medulla secretes the catecholamine hormones norepinephrine and epinephrine (closely related to the sympathetic component of the autonomic nervous system). The Endocrine System

31. The Adrenal Cortex secretes 3 classes of hormones, all steroid hormones: gluticocorticoids mineralocorticoids androgenic hormones One at a time… gluticocorticoids: accounts for 95% of adrenal cortex hormone production  the level of glucose in the blood Released in response to stress, injury, or serious infection - like the hormones from the adrenal medulla. The Endocrine System

32. Mineralocorticoids: work to regulate the concentration of potassium and sodium in the body. (aldosterone) Prolonged  in adrenal cortex hormone results in Cushing’s Disease. Signs & Symptoms of Cushing’s Disease:  in blood sugar levels unusual body fat distribution rapid mood swings The Endocrine System

33. Gonads and Ovaries: the endocrine glands associated with human reproduction. Female ovaries produce eggs Male gonads produce sperm both have endocrine functions. Ovaries: located in the abdominal cavity adjacent to the uterus. Under the control of LH and FSH from the anterior pituitary they manufacture estrogen Protesterone The Endocrine System

34. Estrogen and Progesterone have several functions, including sexual development and preparation of the uterus for implantation of the egg. Day 1 gradual rise of estrogenpromote egg maturation just after peak fall after ovulation, then start up again after menses Day 1 gradual increase progesterone until after ovulation, then if falls to low level for new menses If the egg is fertilized, then the corpus luteum(around the egg, the old follical cells) continues to secrete progesterone. Testes: located in the scrotum produce sperm for reproduction manufacture testosterone - promotes male growth and masculinization Controlled by anterior pituitary hormones FSH and LH. The Endocrine System

35. Endocrine Emergencies: Diabetes Mellitus one of the most common diseases in North America.  insulin secretion by the Beta () cells of the islets of Langerhans in the pancreas. Complications of Diabetes: contributes to heart disease stroke kidney disease blindness The Endocrine System

36. Pathophysiology of Diabetes: Glucose Metabolism Glucose (dextrose) is a simple sugar required by the body to produce energy. Sugars, or carbohydrates, are 1 of 3 major food sources used by the body. The other 2 major food sources are proteins fats Most sugars in the human diet are complex and must be broken down into simple sugars: glucose, galactose and fructose - before use. The Endocrine System

37. Breakdown of sugars is carried out by enzymes in the gastro intestinal system. As simple sugars, these are absorbed from the GE system into the body. More than 95% enter the body as glucose. To be converted into energy, glucose must first be transmitted through the cell membrane. BUT - the glucose molecule is large and doesn’t readily diffuse through the cell membrane. The Endocrine System

38. Glucose must pass into the cell by binding to a special carrier protein on the cell’s surface. Facilitated diffusion - doesn’t use energy. The carrier protein binds with the glucose and carries it into the cell. The rate at which glucose can enter the cell is dependent upon insulin levels. Insulin serves as the messenger - travels via blood to target tissues. Combines with specific insulin receptors on the surface of the cell membrane. The Endocrine System