1. Chapter 9: Endocrine System and Hormone Activity Homeostatic Control through Hormone Release

2. Overview Coordinates and directs the activity of cells. Interacts with the nervous system. Uses chemical messengers called hormones. Controls a variety of necessary biological functions such as: *Reproduction *Growth and Development *Defense *Balance of fluids and electrolytes

3. Mechanism of Action Hormones only affect certain tissues or organs: Hormones bind only to specific sites on the plasma membrane of those Target cells: The Target cell becomes active once the hormone is bound to its specific receptor. Targets Receptors

4. Classifications Amine/Peptide Chemical base is a SINGLE Amino Acid. Acts by activating an enzyme through receptor-binding on the cell membrane. Does NOT enter the cell; remains on the outside of the cell membrane. Lipid/Steroid Chemical base is cholesterol. Acts by directing gene activation in the nucleus. Enters the cell membrane and nucleus of the Target cell because it is lipid-soluble.

5. Hormone Action: What can hormones do? Change the permeability or electrical state of the cell membrane. Synthesize molecules in the cell. Activate/Inactive enzymes. Stimulating, slowing or stopping mitosis

6. Control of Hormone Release Negative Feedback Mechanisms regulate the blood levels of most hormones in 3 ways: 1.Hormonal stimuli 2.Humoral stimuli 3.Neural stimuli

7. Hormonal Stimulation One hormone triggers the release of another hormone. These trigger hormones are TROPHIC HORMONES. Released by the Pituitary Gland in the brain.

9. Humoral Stimulation Blood levels of chemicals triggers the release of specific hormones.

10. Neural Stimulation Nerve fibers (Autonomic Sensory Receptors) trigger the release of specific hormones.

12. Pituitary Gland “The Master Gland” 2 Functional Lobes *Anterior Lobe *Posterior Lobe Interacts closely with the Nervous System through the hypothalamus. Protected by what structure? Sphenoid Bone

13. Anterior Pituitary Regulated through humoral stimulation from the hypothalamus. Many of the hormones released are Trophic Hormones.

14. Anterior Pituitary Hormones Growth Hormone (GH) Thyroid Stimulating Hormone (TSH) Adrenocorticotropin Hormone (ACTH) Follicle Stimulating Hormone (FSH) Luteinizing Hormone (LH) Melanocyte Stimulating Hormone (MSH) Endorphins

15. Too Much Growth Hormone Acromegaly is caused by too much growth hormone AFTER puberty has completed. Gigantism is caused by too much growth hormone during adolescence and puberty.

16. Too Little Growth Hormone The man on the left is 25 years old. The man on the right is 22 years old. The girl below is pictured with her father at the age of 5 years.

17. Abnormal TSH secretion Goiter formation due to inadequate iodine consumption. Exopthalmosis (bulging eyes) due to Graves Disease.

18. Posterior Pituitary Regulated through neural stimulation from the hypothalamus. Produces 2 hormones in response to nervous system stimulation. –Antidiuretic hormone (ADH) –Oxytocin

19. Thyroid Gland Located in the anterior portion of the neck, just below the throat. Releases hormones that act on the metabolic rate. *T 4 : thyroxine *T 3 : triiodothyronine Also produces the calcitonin.

20. Parathyroid Gland Located on the posterior surface of the Thyroid gland. Secretes Parathyroid Hormone (PTH) –The MOST important regulator of blood calcium levels.

21. Adrenal Glands Located on the superior aspect of each kidney. 2 functional parts *Cortex *Medulla Each part secretes a specific type of hormone.

22. Adrenal Gland Divisions CORTEX Produces hormones that control fluid and electrolyte balance. Produces sex hormones. MEDULLA Produces hormones for sympathetic/ parasympathetic nervous system.

23. Pancreas Located in abdominal cavity close to stomach. Produces hormones for the use and storage of glucose –Insulin –Glucagon

24. Pineal Gland Pineal gland is very close to the optic nerve in the brain. Produces Melatonin that activates sleep- wake cycles.

25. Thymus Gland Located behind the sternum. Decrease in size as you age. Produces Thymosin needed for the production of T- lymphocytes. T-cells are needed for protection against viral infections.

26. Ovaries and Testes Hormone producing glands (Gonads) of the female and male reproductive systems. Controls fertility, reproduction, and gestation. Ovaries produce and release estrogen and progesterone Testes produce testosterone and androgens

27. Other Hormone-Producing Organs Placenta Stomach Intestines Heart Striated muscles Skin Adipose/Fat Liver Kidneys Uterus