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 slower acting and regulates processes that occur over days or even months.

3. Hormones Endocrine systems exert control through the use of hormones.
Hormones are 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 systems have 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 hormones function in:. 1) development. 2) bioenergetics
Thyroid hormones function 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

52. Stress and The Adrenal Glands

53. Steroids Androgens: male sex hormones Testosterone:
Stimulate the development and maintenance of male reproductive systems
responsible for secondary male sex characteristics

54. Steroids Estrogens: female sex hormones Progestins (Progesterone)
Maintain the female reproductive system
responsible for secondary sex characteristics
Progestins (Progesterone)
Preparation and maintainace of uterus for reproduction
Gonadotropins from anterior pituitary (FSH and LH) control the synthesis of both androgens and estrogens