1. Chapter 13 The Endocrine System

2. Endocrine Functions: Hormones
Come from endocrine glands
Circulate in the bloodstream
Act on specific cells in the body

3. Endocrine System Characteristics
Access to every cell
The exception is the CNS due to the blood – brain barrier
Each hormone acts only on specific cells (target cells)
Only specific cells have receptors for specific hormones
Endocrine control is slower than nervous system
Endocrine and nervous systems interact

4. Classification of Hormones: Steroid
Steroid hormones
Lipid soluble, chemically derived from cholesterol
Enter target cells
Activate specific genes to produce specific proteins
Slower acting than non-steroid hormones; minutes to hours

5. Steroid Hormone Action on a Target Cell
Figure 13.2

6. Classification of Hormones: Nonsteroid
Nonsteroid hormones
Water soluble
Bind to receptors on target cell membranes
Work through intermediate mechanisms to activate existing enzymes
Faster acting than steroid hormones; seconds to minutes

7. Nonsteroid Hormone Action on a Target Cell
Figure 13.3

8. Role of Negative Feedback Loops
Figure 13.4

9. Hypothalamus and the Anterior Pituitary Gland
A link between the nervous system and the endocrine system
Monitors the hormones secreted by the pituitary gland
Figure 13.7

10. http://www. clarian. org/ADAM/doc/HealthIllustratedEncyclopedia/2/8883
The pancreas functions as both an endocrine gland and an exocrine gland (secretions used in digestion)
Islets of Langerhans
clusters of cells within the pancreas
secrete hormones
The Pancreas

11. Roles of Insulin and Glucagon in Regulating Blood Glucose
Figure 13.10

12. Adrenal Glands: Medulla
Adrenal medulla
Neuroendocrine organ
The hormones are synthesized and stored in specialized cells in the adrenal medulla
Secretion
Sympathetic nervous system
The adrenal medulla is innervated with sympathetic nerves
Hormones: nonsteroidal
Epinephrine and norepinephrine (also serve as neurotransmitters)
Enhance function of sympathetic nervous system (fight-or-flight response)

13. Adrenal Glands: Medulla
Figure 13.11

14. Homeostatic Regulation of Blood Calcium Concentration
Figure 13.15a

15. Homeostatic Regulation of Blood Calcium Concentration (cont.)
Figure 13.15b

16. Thyroid/Parathyroid Glands
Calcitonin (secreted from thyroid)
Lowers blood calcium levels by inhibiting the action of osteoclasts
Parathyroid hormone (PTH): nonsteroidal
Removes calcium and phosphate from bone
Increases absorption of calcium by the digestive tract
Increases renal retention of calcium and excretion of phosphate