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.

6. 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

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

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

11. 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.

12. 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

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

15. Hormonal Control • In Hydra, one hormone stimulates growth and budding while inhibiting sexual reproduction. • Invertebrates exhibit a diversity of hormones which function in 1) homeostasis, 2)reproduction, 3)development, and 4)behavior.

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. Pancreas Endocrine Tissues • Islets of Langerhans: • Alpha cells secrete glucagon • Beta cells secrete insulin • antagonistic hormones that regulate blood glucose

50. If glucose homeostasis is unbalanced: • Type I diabetes mellitus (insulin-dependent diabetes) • Type II diabetes (non-insulin-dependent diabetes) • Both types untreated will result in high blood sugar: • Kidneys excrete glucose • More water is excreted • Fat is the major source of fuel for cell respiration.