1. The Endocrine System

2. System Overview Includes cells, tissues, and organs that secrete hormones directly into the body fluids Endocrine vs. exocrine

3. Functions of Hormones Help regulate metabolic processes Control the rates of some chemical reactions Aid in the transport of substances across membranes Help regulate water and electrolyte balances Play vital roles in reproduction, growth, and development

4. What is a Hormone? A biochemical secreted by a cell to affect the functions of another cell Action of a hormone is restricted to a specific target cell that has protein receptors for the hormone

5. Steroid Hormones Fat soluble Diffuse into cells easily May bind to DNA and activate genes Fast acting

6. Nonsteroid Hormones Usually combine with cell membrane receptors Binding stimulates activity site of receptor (hormone is first messenger) second messengers inside cell trigger cell action

7. Prostaglandins Not really hormones, but behave similarly Affect only the organ where they are produced Present in very small quantities, not stored, and rapidly inactivated

8. Control of Hormone Secretions Hypothalamus Controls the anterior pituitary gland’s release of hormones that stimulate other endocrine glands Nervous system Stimulates some glands directly Some glands respond directly to changes in the internal environment

9. Hormone Regulation Negative feedback mechanisms

10. Major Endocrine Glands and Their Hormones

11. Pituitary Gland Located at the base of the brain Attaches to the hypothalamus by means of the infundibulum Anterior and posterior lobes

12. Anterior Pituitary Gland Dense CT capsule Blocks of glandular epithelium around blood vessels

13. Anterior Pituitary Hormones Growth Hormone (GH) Stimulates most body cells to increase in size and divide Promotes protein synthesis

14. Anterior Pituitary Hormones Thyroid-Stimulating Hormone (TSH) Promotes normal activity and development of the thyroid gland Adrenocorticotropic Hormone (ACTH) Triggers the release of hormones from the adrenal cortex

15. Anterior Pituitary Hormones Follicle-Stimulating Hormone (FSH) Stimulates gamete production in males and females Stimulates maturation of ovarian follicles and eggs in females Luteinizing Hormone (LH) Promotes production of gonadal hormones In females, triggers ovulation and stimulates maturation of ovarian follicles and eggs

16. Anterior Pituitary Hormones Prolactin (PRL) Stimulates milk production in the breasts

17. Posterior Pituitary Gland Consists mostly of nerve fibers and neuroglia Closely associated with the hypothalamus

18. Posterior Pituitary Hormones Oxytocin (OT) Stimulates contraction of uterine muscles Triggers “letdown” of breast milk

19. Posterior Pituitary Hormones Antidiuretic Hormone (ADH) Inhibits urine formation in the kidneys Stimulates constriction of blood vessels Released in response to increased blood solute concentration, low blood pressure, some drugs (nicotine, morphine) Inhibited by alcohol and excessive water consumption

20. Thyroid Gland Highly vascular Two lobes connected by isthmus Located below larynx Secretory parts are follicles filled with colloid

21. Thyroid Hormones Thyroxine (T4) and Triiodothyronine (T3) Collectively known as thyroid hormone Increases metabolic rate and body heat production Regulates tissue growth

22. Thyroid Disorders

23. Thyroid Hormones Calcitonin Lowers blood calcium Inhibits osteoclasts Stimulates osteoblasts

24. Parathyroid Glands 4 small glands on posterior of thyroid gland

25. Parathyroid Hormone Parathyroid Hormone (PTH) Raises blood calcium Stimulates osteoclasts Triggers reabsorption of calcium in urine in kidneys Increases intestinal absorption of calcium from food

26. Adrenal Glands Located on top of kidneys Embedded in adipose Adrenal cortex Outer portion of epithelial cells organized into layers Adrenal medulla Consists of modified neurons around blood vessels and nerves of the sympathetic nervous system

27. Adrenal Cortex Hormones Aldosterone Zona glomerulosa Reduces excretion of sodium from kidneys Increases reabsorption of sodium from urine, perspiration, saliva, and gastric juice Increases excretion of potassium Increases water retention

28. Adrenal Cortex Hormones Cortisol Helps maintain blood glucose concentration between meals Zona fasciculata

29. Adrenal Cortex Hormones Androgens Supplements male sex hormones produced by gonads Zona reticularis

30. Adrenal Medulla Hormones Epinephrine and Norepinephrine Produce short term stress response Increase heart rate, blood pressure, and metabolic rate Dilation of bronchioles Trigger liver to release glucose into bloodstream

31. Pancreas Mixed gland Located behind stomach Islets of Langerhans – masses of endocrine cells amongst acinar (exocrine) cells

32. Pancreas Hormones Insulin Produced by beta cells (stain purple) Decreases blood glucose concentration Enhances absorption of glucose into cells for energy use and storage Glucagon Produced by alpha cells (stain pink) Stimulates liver to release glucose from glycogen 1 molecule triggers the release of 100 million glucose molecules into the blood

34. Ovaries Female gonads Produce estrogen and progesterone: Stimulate maturation of the female reproductive organs and appearance of secondary sexual characteristics

35. Testes Male gonads Produce testosterone: Stimulates maturation of the male reproductive organs and the appearance of male secondary sexual characterisics Increases sex drive Promotes normal sperm production

36. Pineal Gland Located between cerebral hemispheres Attached to thalamus Releases melatonin: Released in response to light Helps regulate circadian rhythms

37. Thymus Gland Located between the lungs posterior to the sternum Butterfly-shaped Diminishes during adulthood Produces thymosin: Essential for the normal development of T cells and the immune response

38. Disorders of all endocrine glands Hyposecretion- too little hormone is released Example: Hypothyroidism= very slow metabolism Hypersecretion- too much hormone is released Example: Acromegaly= too much HGH