Hormones & the Endocrine System

1. Hormones & the Endocrine System Campbell and Reece Chapter 45

5. Hormones • body‘s long-distance regulators • molecules secreted into ECF  circulate thru body  communicate regulatory messages thru out body • in animals that undergo metamorphosis hormones stimulate growth of adult cells & apoptosis of larval cells

6. Endocrine System • with nervous system in charge of communication & regulation thru out body

7. rapid response • neurotransimitters • short distances • regulate neurons, muscle, glands, endocrine cells (area of overlap) • slower response • hormones • short or long distances • regulate functions of most organ systems Nervous System Endocrine System

8. Intercellular Communication • signaling processes in animals: • classified by 2 criteria: • type of secreting cell • route signal takes to reach target

9. Endocrine Signaling • hormones  ECF  bloodstream  target cells • functions: • maintain homeostasis • mediate responses to environmental stimuli • regulates growth & development

11. Local Regulators • molecules that act over short distances • reach target solely by diffusion • ex: cytokines released by T helper cells • 2 types: • paracrine • autocrine

13. animation • http://sites.sinauer.com/cooper5e/animation1501.html

14. Pheromones, an Exception • not all secreted molecules act w/in body • method of communication between members of some animal species • ex: • foraging ant locates new food source  marks its path back to nest with pheromones • define boundaries of territory • attract mates: female giant silk moth releases pheromone that can attracgt a male up to 4.5 km away

15. Endocrine Glands • ductless organs • secrete hormones directly into surrounding fluid

16. 3 Chemical Classes of Hormones • Polypeptide • Steroid • Amines

18. Cellular Response Pathways • secreted by exocytosis • travel thru blood • bind to cell-surface signal receptors  induces changes in cytoplasmic molecules  might alter gene transcription (signal transduction) • diffuse out of endocrine cell  bind to transport molecules in blood  diffuse into target cells  bind to intracellular receptors  trigger gene transcription Water-Soluble Lipid-Soluble

20. Cell-surface hormone receptors trigger signal transduction

21. Steroid hormone receptors directly regulate gene expression

22. Multiple Effects of Hormones • effects hormone has can vary if target cells differ in molecules that receive or produce the response to the hormone

23. Signaling by Local Regulators • pathways by which local regulators trigger responses same as those activated by hormones • growth factors • stimulate cell proliferation & differentiation • NO (nitric oxide) • synthesized & released by endothelial cell when O2 levels low  activates enzyme in smooth muscle  vasodilation  increased blood flow • prostaglendins: • aggregation of platelets  blood clotting • promote fever & inflammation in immune system • smooth muscle contraction

24. Coordination of Neural & Endocrine Signaling • occurs in all but simplest invertebrates

26. Simple Hormone Pathways

27. Simple Neuroendocrine Pathway

28. Feedback Loop Regulations • stimulus initiates a response that will reduce the effect of the stimulus • stimulus initiates a response that reinforces the stimulus Negative Feedback Positive Feedback

30. Target Tissues of Insulin • Insulin lowers blood glucose levels by: • stimulating nearly all cells *outside the brain to take up glucose • slowing glycogen breakdown in liver • inhibiting glycerol (from fats) & a.a.  glucose aka gluconeogenesis • *brain cells do not require insulin to take up glucose

31. Target Tissues of Glucagon • Glucagon influences blood glucose levels mainly thru it effects on target cells in liver • when serum glucose levels < normal (70 – 110 mg/100 mL) glucagon signals liver cells to release glucose  blood by: • increase glycogen hydrolysis • convert a.a. & glycerol  glucose

32. Diabetes Mellitus • deficiency of insulin in target tissues • hi blood glucose levels but cannot get into cells so cells use fat as main substrate for cellular respiration • acidic metabolites form during fat breakdown  ketoacidosis • low pH can be life threatening • Na+ & K+ ions depleted

34. Type II Diabetes: Insulin Resistance • characterized by failure of target cells to take up insulin from blood  elevated blood glucose • 7th most common cause of death in USA • contributing factors: • genetics (defect in insulin receptor or insulin response pathway) • obesity • age (though more children being diagnosed) • sedentary lifestyle

36. Coordination of Endocrine & Nervous Systems in Vertebrates • Hypothalamus • plays central role in integrating endocrine & nervous systems • receives info  initiates endocrine signaling appropriate to environmental conditions • sends releasing hormones to anterior pituitary gland  sends tropic hormones to target glands • sends hormones it makes to posterior pituitary

38. Posterior Pituitary Hormones • ADH: antidiuretic hormone (vasopressin) • 1 of several hormones that act on kidneys • increases water retention in kidneys (decreases urine vol/ increases blood plasma vol : maintains blood osmolaritywnl • Oxytocin • increases strength on uterine contractions in labor • regulates milk secretion by mammary glands

40. Anterior Pituitary Hormones

41. Evolution of Thyroid Function • over time functions of a hormone have diverged from species to species • ex: thyroxine (thyroid hormone) regulates metabolism in most animal but in frogs it function to resorb tadpole tail • Prolactin: in mammals develops mammary glands & milk production but in birds: regulates fat metabolism & reproduction; in amphibians: delays metamorphosis; in fish

42. Prolactin Functions • Animal Function • Mammals develops mammary • ` glands & milk synthesis • Birds regulates fat metabolism • Amphibians delays metamorphosis • Fish regulates salt & water • ` balance

43. Tropic Hormones (not GH orMSH)

44. Nontropic Hormones of Anterior Pituitary: GH