The Endocrine System

1. The Endocrine System Chapter 45

2. All animals exhibit internal communication and control via 2 major systems Nervous System: Endocrine System: high speed electrical messages slower acting chemical messages

3. Chemical Signals include: Pheromones send info. between: individuals Local Regulators send info. between: cells in the immediate vicinity Hormones send info. between body organs to regulate: reproduction, energy metabolism, growth & development

4. Pheromone Information: Communication signals between animals of the same species. Classified by function, for example: mate attractants, territorial markers, alarm substances… Small molecules that are: active in tiny amounts

5. Local Regulator Information: Neurotransmitters: signals sent out from , called signaling. neurons synaptic Histamine & interleukins: signals sent out from , called signaling. paracrine immune system Growth Factors: proteins which must be present in extracellular fluid for cell types to grow & develop Prostaglandins: modified fatty acids, often from plasma membrane (>16 types), functions include inducing labor, fever, inflammation… Nitrous Oxide (gas): highly reactive, causes rapid change in target cells

6. Hormone Information: There are 2 kinds of glands in animals: exocrine and endocrine. Some organs contain BOTH types of glands. Exocrine Glands: use ducts for secretion. Ex. Sweat, mucus (NOT part of the endocrine system!) Endocrine Glands: make hormones but are -- ductless, use bloodstream for transport Endocrinology: study of hormones (>50)

7. Hormones are grouped by similarity in chemical structure into 3 classes: Steroid hormones = fat-soluble, made from cholesterol, includes sex hormones Amines = small, water-soluble, often made from tyrosine, includes epinephrine (adrenaline). Polypeptide hormones = most diverse group, chains of amino acids, includes insulin

8. Hormones are secreted into the _______________ travel through the and are only able to affect their cells Interstitial fluid bloodstream target

9. How Hormones affect cells: Act in very low concentration (tiny amounts) Have different effects on different target cells due to: different receptors or response pathways Cellular Response Pathways = the complex series of steps that occur between hormone-receptor binding and the actual target cell response. Two types: enter target cell and affect Steroid Hormones: gene expression Peptide & A.A. derived Hormones: attach to receptors on target cell surface. Influence the activity of enzymes within cell via second messengers.

10. Pathway for Water-soluble Hormones • Reception: Hormone binds to receptor on target cell surface. • Transduction: Message travels within cell via second messengers. • Response: activation of an _ enzyme __, change in the _ uptake or secretion___ of certain molecules, or rearrangement of the cytoskeleton

11. Second Messengers: Cyclic AMP: (Earl W. Sutherland) Steps in the pathway (enzyme cascade): Hormone binds to the target cell: membrane G protein in membrane binds GTP and converts it to GDP: releasing energy Energy is used by an enzyme to convert ATP to cAMP. adenylatecyclase cAMP relays the message to the cytoplasm, activating other enzymes and causing metabolic changes in the cell cAMP is converted to: an inactive product.

12. Inositol Triphosphate: (IP3) • Hormone binds to the target cell membrane • G protein in membrane activates the enzyme phospholipase • Enzyme cleaves a membrane phospholipid into IP3 and DAG (2nd messengers).

13. IP3 Second messenger causes the release of Ca+ from the endoplasmic reticulum • Many chemical messengers (neurotransmitters, growth factors, some hormones) stimulate responses in their target cells by: increasing the Ca+ ion concentration in the cytoplasm

14. Pathway for Lipid-soluble Hormones Reception: Hormone binds to the target cell receptor within the cytosol Transduction: the hormone-receptor complex moves into the nucleus and interacts with DNA or a DNA-binding protein Response: usually is a change in geneexpression

15. Invertebrate Hormones: Functions include: homeostasis, reproduction, development, behavior The same hormone may: function differently in different species

16. Arthropods are well-researched. Example: Insects Brain Hormones (such as PTTH): Stimulate endocrine glands to produce ecdysteroid Ecdysteroid: triggers molting & metamorphosis

17. Vertebrate Endocrine System: See Table 45.1 on p. 949 (green Table 45.1 on p. 961)! Usually, multiple hormones interact to: coordinate activities Endocrine and nervous systems interact to control each other: many feedback mechanisms Hormones vary in their range of targets: general Sex hormones = Other hormones = more specific Tropic hormones = target other endocrine glands

18. Regulation of Hormone Secretion: • Feedback Regulation: can be positive or negative • Negative-feedback pathways may occur in • ___ antagonistic pairs ___ • Glucose homeostasis example: • Glucagon (from alpha cells of pancreas) targets mainly liver cells to – • Insulin (from beta cells of pancreas) targets nearly all body cells to – increase glucose levels in blood decrease glucose levels in blood via cellular uptake.

19. See Human Endocrine Glands: Figure 45.6, p. 950

20. HYPOTHALAMUS:Region of lower brain • Coordinates endocrine and nervous systems. • Receives signals from nerves throughout the body (including the brain) and initiates endocrine signaling in response.

21. Neurosecretory cells:receive nerve cell signals and release hormones in response Signals from the hypothalamus travel to the: pituitary gland

22. PITUITARY GLAND: At the base of the hypothalamus, has 2 lobes Posterior lobe: Extension of the hypothalamus, stores / secretes hormones produced by hypothalamus: Oxytocin:stimulates uterine contractions, lactation, and maternal behaviors ADH (antidiuretic hormone): promotes water re-absorption by: kidneys

23. Anterior lobe: Controlled by hormones of the hypothalamus Controlling hormones are either releasing or inhibiting (some anterior hormones are controlled by both)

24. Makes 4 tropic hormones – stimulate other endocrine glands TSH (thyroid stimulating hormone) ACTH (adrenocorticotropin): controls adrenal cortex (kidney) FSH (follicle stimulating hormone): control gonads LH (luteinizing hormone): control gonads

25. One hormone with some tropic behavior: GH (growth hormone): promotes growth directly and stimulates ______to produce somatomedins which stimulate cartilage and bone growth liver Two Nontropic hormones: • PRL (prolactin): diverse effects in different vertebrates – stimulates milk production & secretion • MSH (melanocyte-stimulating hormone): diverse effects in different vertebrates – mammals = inhibits hunger, others = coloration

26. THYROID: 2 lobes, ventral tracheal surface, activity is controlled by the hypothalamus and pituitary in a negative feedback loop. Important for vertebrate and development metabolism Triiodothyronine (T3) & Thyroxine (T4): Both made with iodine. Deficiency = goiter controldevelopment & metabolism Calcitonin: lowers Calcium levels in blood (homeostasis)

27. Grave’s disease Hyperthyroidism = __________ Hypothyroidism (treat with T4) = lethargy, weight gain, cold intolerance

28. PARATHYROID: 4 GLANDS, embedded in thyroid Important for calcium ion homeostasis. PTH (parathyroid hormone): raises blood levels of Ca2+ (opposite of calcitonin) • Needs vitamin D to work.

29. PANCREAS: Mostly exocrine (digestive secretions) Islets of Langerhans = clusters of endocrine cells (α and β cells)

30. ADRENAL GLANDS:Apex of kidneys. In mammals, Each one really = two gland types: Adrenal cortex (outer region): Responds to ACTH from pituitary. Secretes corticosteroids, 2 main types: Glucocorticoids: Mineralocorticoids promote glucose synthesis from non-carbohydrate sources regulate water & salt balance Also secretes small amounts of sex hormones (steroids)

31. Adrenal medulla (inner region): Stimulated by Nervous System, Makes catecholamines from tyrosine – • Epinephrine (adrenaline) and Norepinephrine: Allow for “flight or fight” response • BOTH Increase the amount of: • Promote glucose release from liver, glycogen breakdown, and fatty acid release from fat cells chemical energy available for immediate use

32. Affect cardiovascular and respiratory systems: Increase heart rate, stroke volume, oxygen delivery Epinephrine mainly controls heart and metabolic rates Norepinephrine mainly controls blood pressure

33. testes & ovaries GONADS: Affect growth & development, regulate reproductive cycles and behaviors. All types are found in BOTH males and females, but in different proportions. Androgens: Responsible for male reproductive system (development & maintenance) Ex. = testosterone Estrogens: Responsible for female reproductive system (development & maintenance) Ex. = estradiol Progestins: Responsible for uterus maintenance Ex. = progesterone

34. Pineal Gland: small mass of tissue near the Center of the brain – Primary source of melatonin – nighttime release is regulated by day length, involves biological clocks

35. Human Female Reproductive Cycle: STUDY Figure 46.13, p.976 (green Figure 46.15, p.988) Be sure you understand length of cycle & hormonal control of events!