Chemical Signals in Animals: Endocrine System and Hormonal Control

1. Chemical Signals in Animals:Endocrine System and Hormonal Control

2. Endocrine vs. Nervous • The nervous system brings about immediate responses, but the endocrine system is sloweracting and regulates processes that occur over days or even months.

3. Hormones • Endocrine systems exert control through the use of hormones. • Hormonesare chemical messengers produced by ductless glands in one part of the body which travel through the bloodstream and exert their influence in another part of the body.

4. Hormones • Hormones are secreted into the bloodstream and regulate whole body processes like growth, reproduction, complex behaviors including courtship and migration. • Hormones influence the metabolism of their target cells by binding to receptor proteins within the cell or on the surface of the cell.

5. Chemical Communication Briefly describe the two major forms of intercellular communication in animal bodies. Which organ systems are responsible for this communication? Describe the type of intercellular communication called “neuroendocrine”. What defines a “target tissue”?

6. Basic Mechanisms of Chemical Signaling

7. Exocrine vs. Endocrine • Exocrine systemshave ducts used for transport of substances directly into the body cavities: salivary glands • Endocrine systems are ductless and secrete hormones directly into body fluids: pituitary gland

8. Hormones The endocrine and the nervous systems are related 1) structurally 2) chemically 3) functionally simultaneously maintaining homeostasis, physiology and other body processes.

10. Hormones • Neurosecretory cells: specialized nerve cells that secrete hormones located within endocrine organs and tissues.

12. Hormones • Several chemicals serve as both neurotransmitters and hormones. • Epinephrine, produced by the adrenal medulla, acts as the “fight or flight hormone” and a neurotransmitter.

13. Control • Positive and Negative Feedback regulate mechanisms of both systems • Positive feed back: output intensifies and increases the likelihood of a response • Mammal milk production and release

14. Control: - Antagonistic hormones work in opposition to one other. - Insulin and glucagon

16. Hormonal Control • Chemical signals operate at virtually all levels of organization: • Local regulators • Intracellular • Cell to cell • Tissue to tissue regulators • Organ to organ regulators • Organism to organism (pheromones)

17. Hormonal Control • Local regulators affect neighboring target cells • Histamine -- immune and regulatory responses • Interleukins– immune response • Growth factors – peptides and proteins that regulate the behavior of cells in growing and developing tissues • Prostaglandins – modified fatty acids released into interstitial fluid

18. Hormonal Control • Binding of a chemical signal to a specific receptor protein triggers chemical events in the target cell that result in a change in that cell. • The response to a chemical signal depends on the number and affinity of the receptor proteins.

20. Chemical Signals • Chemical signals often bind to a specific protein receptor on the plasma membrane of the target cell • Because of their chemical nature, most signal molecules (peptides, proteins, glycoproteins) are unable to diffuse through the plasma membrane

21. Chemical Signals • The binding of the signal molecule to a plasma membrane receptor initiates a signal transduction pathway, a series of events that converts the signal into a specific cellular response.

22. Chemical Signals • A specific example is the binding on the polypeptide hormone insulin to the insulin receptor: • Insulin binding initiates a chain of events that accounts for the blood sugar lowering effects of insulin.

23. Vertebrate Endocrine System Coordinates: 1)metabolism, 2)growth, 3)development, and 4)reproduction.

24. Major Endocrine Organs

25. Functions of Vertebrate Hormones • Some hormones have a single action while other have multiple functions • Tropic hormones act on other endocrine glands

26. Functions of Vertebrate Hormones:

27. Functions of Vertebrate Hormones:

28. Hypothalamus • Region of the lower brain • Receives information from nerves throughout the body and brain • Initiates endocrine signals appropriate to the environmental conditions • Regulates the Pituitary Gland

29. Pituitary Gland - Located at the base of the hypothalamus -Two lobes: anterior and posterior; numerous functions

30. Anterior Pituitary Gland

31. Anterior Pituitary Gland • Produces many different hormones • Regulated by factors of the hypothalamus • Four are tropic hormones that stimulate other endocrine glands to synthesize and release their hormones: TSH, ACTH, FSH, LH

32. Anterior Pituitary Gland • Luteinizing Hormone (LH) • Stimulates ovulation and corpus luteum formation in females • Stimulates spermatogenesis in males

33. Anterior Pituitary Gland • Follicle-Stimulating Hormone (FSH) • Tropic hormone that affects the gonads • In males, necessary for spermatogenesis • In females, it stimulates ovarian follicle growth

34. Anterior Pituitary Gland • Growth Hormone (GH) • Promotes growth directly • Stimulates production of growth factors

35. Anterior Pituitary Gland • Thyroid-Stimulating Hormone (TSH) • Tropic hormone that stimulates the thyroid gland to produce and secrete its own hormone

36. Anterior Pituitary Gland • Adrenocorticotropin (ACTH) stimulates the adrenal cortex to produce and secrete its steroid hormones • Melanocyte-Stimulating Hormone (MSH) regulates the activity of pigment-containing skin cells • Endorphins inhibit pain perception

37. Posterior Pituitary Gland

38. Posterior Pituitary Gland • Synthesized in hypothalamus • Secreted from posterior pituitary • Oxytocin – induces uterine muscle contraction; induces lactation • Antidiuretic Hormone – acts on kidneys to increase water retention thus reducing urine volume

39. Pineal Gland • Small mass near the center of the brain • Produces melatonin • modified amino acid that modulates skin pigmentation • secreted only at night; larger amounts secreted in winter • Involved in regulation of biorhythms

40. Thyroid hormonesfunction in: 1) development 2) bioenergetics 3) homeostasis

41. Thyroid is on the ventral side of the trachea. • plays a major role in vertebrate development: participates in embryonic development • control metamorphosis in amphibians

42. Thyroid gland maintains homeostasis in mammals including: • blood pressure • heart rate • muscle tone • digestion • reproductive functions • rate of O2 consumption and metabolism (increases)

43. Serious metabolic disorders result from deficiency or excess of thyroid hormones. • Hyperthyroidism - high body temperature, sweating, weight loss, irritability, high blood pressure • Hypothyroidism – can cause cretinism in infants and weight gain, lethargy, and cold-intolerance in adults • Goiter - enlarged thyroid caused by a deficiency in iodine

44. Thyroid hormone secretion is regulated by hypothalamus and pituitary. • Negative Feedback System. • Hypothalamus secretes TRH  • Anterior Pituitary stimulated to produce TSH  • TSH binds to receptors and T3 and T4 • High levels of T3, T4, and TSH inhibit TRH

46. Parathyroid hormone (PTH) • balances blood calcium • needs vitamin D to function

48. Adrenal Glands: • located on top of kidneys • Adrenal medula synthesizes catecholamines: • epinephrine • norepinephrine • Glucose is mobilized • Heart rate is increased • Bronchioles dilate

50. Adrenal Glands: • Adrenal cortex synthesizes and secretes corticosteroids as directed by ACTH from the anterior pituitary • Mineralocorticoids affect salt and water balance • Aldosterone stimulates kidney cells to reabsorb sodium ions and water • Glucocorticoids – promote glucose synthesis from noncarbohydrate substances such as proteins