Endocrine System

1. Endocrine System Chapter 26

2. Objectives • the role of hormones in the human body • how the endocrine system differs from the nervous system • endocrine glands, target cells, neurosecretory cells • the difference between steroid and non-steroid hormones • be able to name and identify the location of all of the human endocrine glands • the multiple endocrine functions of the hypothalamus and pituitary • how the anterior pituitary differs from the posterior pituitary in their regulation and types of hormones released • Explain how the thyroid regulates development and metabolism through the release of TSH • Explain how homeostasis of calcium and glucose levels is maintained through antagonistic hormones • Explain the symptoms and treatments of two types of diabetes mellitus and hypoglycemia • Compare and contrast how the adrenal glands mobilize responses to short term and long term stress

3. Hormones • Chemical messengers that regulate body activities • Transported in the circulatory system • Secreted by endocrine glands Intro to endocrine system (2.5 min): http://www.youtube.com/watch?v=HrMi4GikWwQ

4. The Endocrine System

5. The Endocrine System • Some glands are solely endocrine in function (eg. thyroid and pituitary glands) • Some organs have both exocrine and endocrine functions (eg. pancreas) • Some organs function mainly as non-endocrine glands, but may produce some hormones (eg. stomach)

6. Endocrine glands: http://www.youtube.com/watch?v=IVUG74D1BzQ

7. Peptide Hormones • Hydrophilic, water-soluble • Bind to receptors located on the cell membrane • Activation of receptor proteins cause relay molecules to convert extracellular chemical signals to intracellular responses • Activates membrane proteins (eg. channel proteins or enzymes)

9. Peptide hormones (1 min): https://www.youtube.com/watch?v=iUworCsaHos

10. Steroid hormones • Hyrdophobic, lipid-soluble • Bind to receptors inside the cell • Receptors are located in the cytoplasm or nucleus • Receptor-hormone complex activates genes by acting as transcription factors • Stimulates transcription of genes to RNA, which are translated into proteins

11. Steroids (2 min): https://www.youtube.com/watch?v=m9jOXiYdMeY

12. Neuroendocrine Control • Regulation of the pituitary gland by the hypothalamus • Hypothalamus receives information from nerves about external and internal conditions to help maintain homeostasis • Controls the endocrine system by causing the pituitary gland to secrete regulatory hormones for other endocrine glands

13. Endocrine and Nervous System

14. Neurosecretory cells perform functions in both nervous and endocrine systems • Conduct nerve signals AND secrete hormones (eg. Epinephrine/adrenaline)

16. Regulation of Posterior Pituitary • Direct stimulation by nerve axons cause the release of hormones

17. Posterior Pituitary Hormones • Oxytocin • Stimulates uterine contraction and milk release 2. ADH • Stimulates water reabsorption in the kidneys

19. Regulation of Anterior Pituitary • Portal capillary system between the hypothalamus and anterior pituitary • Releasing hormones stimulate the release of hormones • Release-inhibiting hormones inhibit the release of hormones

20. Anterior pituitary (1 min): https://www.youtube.com/watch?v=saQ07ZMfrIc

21. TSH • Hypothalamus releases TRH to stimulate the release of TSH in the anterior pituitary • TSH stimulates the thyroid gland to release triiodothryroxine (T3) and thyroxine (T4) • T3 andT4 regulate bone and nerve cell development, cell metabolim, and maintain homeostasis • Negative feedback system regulates the release of T3 andT4

22. TSH: http://www.youtube.com/watch?v=Vae5CcaPN_8

24. Calcium Homeostasis • Calcium is needed for nerve conduction, muscle contraction, blood clotting and many other body functions • Thyroid and parathyroid glands work together by releasing antagonistic hormones to regulate calcium levels (10 mg/100 ml)

25. Parathyroid Hormone • The parathyroid secretes hormones (PTH) to increase calcium levels • PTH stimulates osteoclasts to release Ca2+ from bones • Kidneys activate Vitamin D to act as a hormone to stimulate Ca2+ reabsorption in the kidneys and Ca2+ uptake in the intestines

27. Calcitonin • The thyroid secretes Calcitonin to decrease Ca2+ levels • Calcitonin stimulates osteoblasts to deposit Ca2+ in the bones • Calcitonin inhibits PTH so kidneys reabsorb less Ca2+ and intestines have lower uptake of Ca2+

28. Calcitonin rap (1 min): https://www.youtube.com/watch?v=GD09nms1McA

29. Glucose Homeostasis • The pancreas releases antagonistic hormones to regulate glucose levels (90 mg/100 ml) • Islets of Langerhans secrete insulin when glucose levels are high, and they secrete glucagon when glucose levels are low.

30. Insulin • Beta cells in the pancreas secrete more insulin to lower blood glucose • Body cells increase glucose uptake due to the activation of more glucose carriers in the cell membrane • The liver and skeletal muscles convert excess glucose into glycogen • Glucose metabolism and conversion of glucose to fat or proteins increases in cells

31. Insulin (2.5 min): https://www.youtube.com/watch?v=OlHez8gwMgw&t=66s

32. Glucagon • Alpha cells in the pancreas release glucagon to increase blood glucose levels • Liver cells convert glycogen, amino acids, and fats to glucose

35. Diabetes Mellitus Insufficient insulin is produced, or insulin receptors in body cell membranes do not recognize insulin Blood glucose levels rise since cells cannot uptake enough glucose Cells are glucose deficient and do not have enough fuel for cell metabolism

36. Type I Diabetes • Autoimmune disease where WBCs attack and destroy pancreatic beta cells • Usually occurs in early childhood • Not enough insulin is produced, resulting in increased blood glucose concentration • Requires insulin injections to regulate glucose levels

37. Type II Diabetes • Usually due to reduced recognition of insulin in the receptors of target cells • Risk factors include obesity, sedentary lifestyle, smoking, unhealthy diet • Occurs usually in late adulthood (40s) • Improving diet and exercise can control glucose levels • Some patients may need to take glucophage medication

39. Symptoms

40. Hypoglycemia • Beta cells secrete too much insulin • Glucose levels drop below normal • Symptoms include hunger, weakness, sweating, nervousness, and dizziness • In severe cases, may result in convulsions, unconsciousness and even death

42. Stress Response • Stress stimuli activate neurons to send signals to the hypothalamus • The hypothalamus stimulates the adrenal gland to release stress-response hormones

43. Adrenal Medulla • Secretes epinephrine and norepinephrine for short-term stress response (“Fight or Flight”) • Liver converts glycogen, fats and proteins to glucose • Increase respiratory rate, heart rate, blood pressure and metabolic rate • Blood vessels in brain and skeletal muscles dilate • Blood vessels in digestive tract and under skin constrict • Bronchioles and pupils dilate

44. Stress response (1 min): https://www.youtube.com/watch?v=BIfK0L8xDP0

45. Cortisol • Adrenal cortex secretes cortisol for slower, longer-lasting response to stress • Increases glucose levels and blood pressure • Prolonged release of cortisol can lead to weight gain, reduced brain function, and other stress-related disorders

46. ACTH • Hypothalamus stimulates the anterior pituitary to secrete Adrenocorticotropic hormone (ACTH) • ACTH stimulates adrenal cortex to secrete corticosteroids to regulate water, salt and glucose levels

48. Corticosteroids • Mineralcorticoids: • Regulate salt and water balance • Eg. Aldosterone stimulates kidneys to reabsorb sodium and water when blood volume and pressure are low

49. Corticosteroids 2. Glucocorticoids: • Promote glucogenesis (formation of glucose from proteins and fats) • High levels can stimulate inflammatory response

50. Sex Hormones • Secreted by gonads (ovaries or testes) • Categorized as estrogens, progestins, androgens • Females have a higher ratio of estrogens to androgens • Males have a higher ratio of androgens to estrogens