1. Hormonal Action and Feedback Loops
Understanding how certain hormones work in the body
What exactly is “feedback”?

2. Thyroid Gland Found at the base of the throat
Consists of two lobes and a connecting isthmus
Produces two hormones
Thyroid hormone
Calcitonin

3. Thyroid Gland
Figure 9.7a

4. Thyroid Gland Thyroid hormone Major metabolic hormone
Composed of two active iodine-containing hormones
Thyroxine (T4)—secreted by thyroid follicles
Triiodothyronine (T3)—conversion of T4 at target tissues

5. Thyroid Gland Thyroid hormone disorders Goiters Cretinism
Thyroid gland enlarges due to lack of iodine
Salt is iodized to prevent goiters
Cretinism
Caused by hyposecretion of thyroxine
Results in dwarfism during childhood

6. Thyroid Gland Thyroid hormone disorders (continued) Myxedema
Caused by hypothyroidism in adults
Results in physical and mental slugishness
Graves’ disease
Caused by hyperthyroidism
Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos

7. Thyroid Gland Calcitonin
Decreases blood calcium levels by causing its deposition on bone
Antagonistic to parathyroid hormone
Produced by parafollicular cells
Parafollicular cells are found between the follicles

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

9. Regulation of Calcium levels in the blood….

10. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Imbalance
Figure 9.10, step 1

11. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland
Imbalance
Figure 9.10, step 2

12. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland releases calcitonin
Calcitonin
Thyroid gland
Imbalance
Figure 9.10, step 3

13. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland releases calcitonin
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Thyroid gland
Imbalance
Figure 9.10, step 4

14. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood
Ca2+ levels
Thyroid gland releases calcitonin
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Thyroid gland
Figure 9.10, step 5

15. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 6

16. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Thyroid gland
Parathyroid glands
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 7

17. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
PTH
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 8

18. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Osteoclasts
degrade bone matrix and release Ca2+ into blood
PTH
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood
Ca2+ levels
Imbalance
Figure 9.10, step 9

19. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Osteoclasts
degrade bone matrix and release Ca2+ into blood
PTH
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Figure 9.10, step 10

20. Hormonal Regulation of Calcium in Blood
Calcium homeostasis of blood 9–11 mg/100 ml
Rising blood Ca2+
levels
Thyroid gland releases calcitonin
Osteoclasts degrade bone matrix and release Ca2+ into blood
PTH
Calcitonin
Calcitonin stimulates calcium salt deposit in bone
Parathyroid glands release parathyroid hormone (PTH)
Thyroid gland
Parathyroid glands
Falling blood Ca2+ levels
Imbalance
Figure 9.10, step 11

21. Hormones of the Adrenal Gland…

22. Adrenal Glands Sit on top of the kidneys Two regions
Adrenal cortex—outer glandular region has three layers
Mineralocorticoids secreting area
Glucocorticoids secreting area
Sex hormones secreting area
Adrenal medulla—inner neural tissue region

23. Hormones of the Adrenal Cortex
Figure 9.11

24. Hormones of the Adrenal Cortex
Mineralocorticoids (mainly aldosterone)
Produced in outer adrenal cortex
Regulate mineral content in blood
Regulate water and electrolyte balance
Target organ is the kidney
Production stimulated by renin and aldosterone
Production inhibited by atrial natriuretic peptide (ANP)

25. Action Within the Adrenal Cortex
Figure 9.12

26. Hormones of the Adrenal Cortex
Glucocorticoids (including cortisone and 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

27. Hormones of the Adrenal Cortex
Sex hormones
Produced in the inner layer of the adrenal cortex
Small amounts are made throughout life
Mostly androgens (male sex hormones) are made but some estrogens (female sex hormones) are also formed

28. Adrenal Gland Disorders
Adrenal cortex disorders
Addison’s disease
Results from hyposecretion of all adrenal cortex hormones
Bronze skin tone, muscles are weak, burnout, susceptibility to infection
Hyperaldosteronism
May result from an ACTH-releasing tumor
Excess water and sodium are retained leading to high blood pressure and edema

29. Adrenal Gland Disorders
Adrenal cortex disorders
Cushing’s syndrome
Results from a tumor in the middle cortical area of the adrenal cortex
“Moon face,” “buffalo hump” on the upper back, high blood pressure, hyperglycemia, weakening of bones, depression
Masculinization
Results from hypersecretion of sex hormones
Beard and male distribution of hair growth

30. Hormones of the Adrenal Medulla
Produces two similar hormones (catecholamines)
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
These hormones prepare the body to deal with short-term stress (“fight or flight”) by
Increasing heart rate, blood pressure, blood glucose levels
Dilating small passageways of lungs

31. Hormones of the Adrenal Cortex
Figure 9.11

32. How important is the Pancreas??

33. Pancreatic Islets
The pancreas is a mixed gland and has both endocrine and exocrine functions
The pancreatic islets produce hormones
Insulin—allows glucose to cross plasma membranes into cells from beta cells
Glucagon—allows glucose to enter the blood from alpha cells
These hormones are antagonists that maintain blood sugar homeostasis

34. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Figure 9.15, step 1

35. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts)
Imbalance
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Figure 9.15, step 2

36. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Elevated blood sugar levels
Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts)
Imbalance
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Figure 9.15, step 3

37. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Insulin-secreting cells of the pancreas activated; release insulin into the blood
Elevated blood sugar levels
Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts)
Imbalance
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Figure 9.15, step 4

38. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Insulin-secreting cells of the pancreas activated; release insulin into the blood
Uptake of glucose from blood is en- hanced in most body cells
Elevated blood sugar levels
Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts)
Imbalance
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Figure 9.15, step 5

39. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Insulin-secreting cells of the pancreas activated; release insulin into the blood
Uptake of glucose from blood is en- hanced in most body cells
Elevated blood sugar levels
Liver takes up glucose and stores it as glycogen
Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts)
Imbalance
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Figure 9.15, step 6

40. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Insulin-secreting cells of the pancreas activated; release insulin into the blood
Uptake of glucose from blood is en- hanced in most body cells
Blood glucose levels decline to set point; stimulus for insulin release diminishes
Elevated blood sugar levels
Liver takes up glucose and stores it as glycogen
Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts)
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Figure 9.15, step 7

41. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Stimulus: declining blood glucose levels (e.g., after skipping a meal)
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Figure 9.15, step 8

42. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Stimulus: declining blood glucose levels (e.g., after skipping a meal)
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Low blood sugar levels
Figure 9.15, step 9

43. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Stimulus: declining blood glucose levels (e.g., after skipping a meal)
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Low blood sugar levels
Glucagon-releasing cells of pancreas activated; release glucagon into blood; target is the liver
Figure 9.15, step 10

44. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Stimulus: declining blood glucose levels (e.g., after skipping a meal)
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Imbalance
Low blood sugar levels
Glucagon-releasing cells of pancreas activated; release glucagon into blood; target is the liver
Liver breaks down glycogen stores and releases glucose to the blood
Figure 9.15, step 11

45. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Stimulus: declining blood glucose levels (e.g., after skipping a meal)
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Low blood sugar levels
Rising blood glucose levels return blood sugar to homeostatic set point; stimulus for glucagon release diminishes
Glucagon-releasing cells of pancreas activated; release glucagon into blood; target is the liver
Liver breaks down glycogen stores and releases glucose to the blood
Figure 9.15, step 12

46. Homeostasis: Normal blood glucose levels (90 mg/100ml)
Insulin-secreting cells of the pancreas activated; release insulin into the blood
Uptake of glucose from blood is en- hanced in most body cells
Blood glucose levels decline to set point; stimulus for insulin release diminishes
Elevated blood sugar levels
Liver takes up glucose and stores it as glycogen
Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts)
Imbalance
Homeostasis: Normal blood glucose levels (90 mg/100ml)
Stimulus: declining blood glucose levels (e.g., after skipping a meal)
Imbalance
Low blood sugar levels
Rising blood glucose levels return blood sugar to homeostatic set point; stimulus for glucagon release diminishes
Glucagon-releasing cells of pancreas activated; release glucagon into blood; target is the liver
Liver breaks down glycogen stores and releases glucose to the blood
Figure 9.15, step 13