Major Endocrine Organs

1. Major Endocrine Organs Figure 16.1

2. The Endocrine System

3. I. Overview of the Endocrine System • The endocrine system is a control system in the body “endocrine” means “internal secretion” (i.e. into the internal environment) • Nervous system regulates with action potentials • Fast transmission, but short-lived • Endocrine system regulates by chemical messengers (hormones) that are released into the blood • Slow distribution, but effect lasts longer

4. Hormones bind only to target cells

5. e.g. cell development (regional) e.g. synaptic signals, development of spinal cord

6. B) Hormones of the endocrine system control several major processes • Reproduction: sperm & egg production; pregnancy; birth of offspring • Development: puberty • Growth: of cell size & mitosis • Metabolism: usage of energy for cell activities • Body defense: activation of WBC

7. C) The Chemistry of Hormones • Amino acid-based hormones • Proteins • Peptides • Amines • Steroid hormones – made from cholesterol • Prostaglandins –local hormones made from highly active lipids

8. Major Endocrine Organs Figure 16.1

11. A) Pituitary Gland • Size of a grape • Hangs by a stalk from the hypothalamus • Protected by the sphenoid bone • Has two functional lobes • Anterior pituitary – glandular tissue • Posterior pituitary – nervous tissue

12. Hormones of the Anterior Pituitary Figure 9.4

13. Hormones of the Anterior Pituitary • Six anterior pituitary hormones • Two affect non-endocrine targets (GH, PRL) • Four stimulate otherendocrine glands (ACTH, TSH, LH, FSH) Note: “tropic” hormones from the hypothalamus [Table 13.2] stimulate other endocrine glands to release hormones • Characteristics of all anterior pituitary hormones • Proteins (or peptides) • Act through second-messenger systems

14. 1) Growth Hormone (GH) • General metabolic hormone • Major effects are directed to growth of skeletal muscles and long bones • Causes amino acids to be built into proteins • Causes fats to be broken down for a source of energy

15. Wadlow reached 8 ft 11 in and weighed 439 lbs at his death at age 22. His great size and his continued growth in adulthood was due to hypertrophy of his pituitary gland, which resulted in an abnormally high level of human growth hormone. He showed no indication of an end to his growth even at the time of his death. Robert Wadlow next to his brother, in 1936

16. 2) Prolactin (PRL) • Stimulates and maintains milk production following childbirth 3) Adrenocorticotropic hormone (ACTH) • Regulates endocrine activity of the adrenal cortex 4) Thyroid-stimulating hormone (TSH) • Influences growth and endocrine activity of the thyroid

17. Gonadotropic hormones 5) Follicle-stimulating hormone (FSH) • Stimulates follicle development in ovaries • Stimulates sperm development in testes

18. 6) Luteinizing hormone (LH) • Triggers ovulation • Causes ruptured follicle to become the corpus luteum • Stimulates testosterone production in males (as interstitial cell-stimulating hormone, ICSH)

19. Hormones of the Posterior Pituitary Figure 9.5

20. Hormones of the Posterior Pituitary 7) Oxytocin • Stimulates contractions of the uterus during labor • Causes milk ejection 8) Antidiuretic hormone (ADH) • Can inhibit urine production • causes vasoconstriction leading to increased blood pressure (vasopressin)

21. Thyroid Gland • Found at the base of the throat • Consists of two lobes and a connecting isthmus

22. Thyroid Hormone • Composed of two active iodine-containing hormones • Both increase cell metabolism which produces heat and provides chemical energy for daily activities 9) Thyroxine (T4) 10)Triiodothyronine (T3) [trahy-ahy-oh-doh-thahy-ruh-neen]

23. 11) Calcitonin • Decreases blood calcium levels by causing its deposition on bone • Antagonistic to parathyroid hormone

25. Parathyroid Glands • Tiny masses on the posterior of the thyroid 12) parathyroid hormone • Stimulate osteoclasts to remove calcium from bone • Stimulate the kidneys and intestine to absorb more calcium • Raise calcium levels in the blood

27. Adrenal Glands • Sit on top of the kidneys • Two regions • Cortex – outer glandular region in three layers (also secretes a small amount of sex hormones) • Medulla – inner neural tissue region

28. 13) aldosterone • Produced in outer adrenal cortex • Regulate mineral content in blood, water, and electrolyte balance • Target organ is the kidney • works together with renin secreted by the kidney

29. Hormones of the Adrenal Cortex Aldosterone reduces urine production (by causing Na+ and water retention)

30. 14) cortisol • Produced in the middle layer of the adrenal cortex • Promote normal cell metabolism • Help resist long-term stressors • Released in response to increased blood levels of ACTH

31. Hormones of the Adrenal Medulla 15) Epinephrine 16) Norepinephrine • produced in the adrenal medulla • are similar hormones (catecholamines) • prepare the body to deal with short-term stress

32. Roles of the Hypothalamus and Adrenal Glands in the Stress Response

33. Pancreas The pancreas is a mixed gland 17) Insulin – allows glucose to cross plasma membranes into cells; from beta cells 18) Glucagon – allows glucose to enter the blood; from alpha cells • These two hormones are antagonists that maintain blood sugar homeostasis • produced by the Islets of the Langerhans

34. Pancreatic Islets Figure 9.13

35. Pancreatic Hormones and Blood Sugar Figure 9.14

36. 19) Somatostatin–inhibits secretion of insulin & glucagon

37. Pineal Gland near roof of the third ventricle of the brain 20) melatonin • Helps establish the body’s wake and sleep cycles

39. Thymus • Located posterior to the sternum • Largest during infant and child stages

40. 21) thymosin • Matures some types of white blood cells • Important in developing the immune system

41. Hormones of the Ovaries 22) Estrogens • Produced by Graafian follicles or the placenta • Stimulates the development of secondary female characteristics • Matures female reproductive organs • Helps prepare the uterus to receive a fertilized egg • Helps maintain pregnancy • Prepares the breasts to produce milk

42. Hormones of the Ovaries 23) Progesterone • Produced by the corpus luteum • Acts with estrogen to bring about the menstrual cycle • Helps in the implantation of an embryo in the uterus

43. Hormones of the Testes • Interstitial cells of testes are hormone-producing • Produce several androgens 24) Testosterone is the most important androgen • Responsible for adult male secondary sex characteristics • Promotes growth and maturation of male reproductive system • Required for sperm cell production

44. Other Hormone-Producing Tissues and Organs • Parts of the small intestine • Parts of the stomach • Kidneys • Heart • Many other areas have scattered endocrine cells

45. Hormone Overview • Hormones are produced by endocrine glands • Cells secrete hormones into extracellular fluids • Blood transfers hormones to target sites • These hormones regulate the activity of other cells

46. Extra slides . . .

47. Endocrine Function of the Placenta • Produces hormones that maintain the pregnancy • Some hormones play a part in the delivery of the baby • Produces HCG in addition to estrogen, progesterone, and other hormones

48. PRACTICE QUIZ How many endocrine glands are there? What type of chemical do endocrine glands secrete? Name all the endocrine glands. Name as many hormones as you can!

49. Check your answers!  How many endocrine glands are there? *10 What type of chemical do endocrine glands secrete? *hormones What are three different functions of these chemicals? *hormones Name all the endocrine glands * hypothalamus, pituitary, pineal, thyroid, parathyroid, thymus, pancreas, adrenal, ovary, testis Name as many hormones as you can.

50. Developmental Aspects of the Endocrine System • Most endocrine organs operate smoothly until old age • Menopause is brought about by lack of efficiency of the ovaries • Problems associated with reduced estrogen are common • Growth hormone production declines with age • Many endocrine glands decrease output with age