Integration and Control:

1. Integration and Control: THE ENDOCRINE SYSTEM Campbell & Reece Chapter 45

2. Endocrine • Hormones: substances produced by particular tissues of the body carried by the bloodstream to "target cells," upon which they exert special effects • *Hormones are secreted by glands, made mostly of epithelial tissue • Exocrineglands: secrete into ducts (sweat glands, digestive glands) • Endocrineglands: secrete hormones (into bloodstream) "ductless glands" • Endocrine Gland--->hormone--> Bloodstream------> target organ/tissue

3. Hormones may be: • Steroids • Peptides/proteins; • Amino acids • Active in very small quantities • Controlled by: • Negative Feedback • Rapid degradation by the body Hormonal communication http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter20/animation__hormonal_communication.html

4. Positive & Negative feedback • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter20/animation__positive_and_negative_feedback__quiz_1_.html

5. Mechanisms of Action of Hormones: 2 Main ways that Hormones Effect Target Cells: Intracellular receptor molecules- steroids, thyroid hormones Membrane receptor molecules- amino, peptide, protein hormones A.  Intracellular Receptors • Steroid hormones and thyroid hormones are soluble in lipids and pass freely through cell membranes; must contact receptor site with in a cell • This changes a cell’s actions (protein synthesis, etc.) B.  Membrane Receptors • Combine with receptors on or in the membrane target cells • Once combined, send a second messenger inside ? to the nucleus (cyclic AMP) • May simply increase/decrease a cell’s permeability to substances Action of Steroid Hormones http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120109/bio46.swf::Mechanism%20of%20Steroid%20Hormone%20Action

6. The Hypothalamus-Pituitary Axis: • Pituitary was once considered the "master gland" until it was learned that it was under control of the hypothalamus (brain region) • The hypothalamus makes several hormones which travel to and are released by the pituitary lobes. • Target tissues are stimulated by (or inhibited by) release of these hormones into the bloodstream.

8. The Hypothalamus-Pituitary Axis: • PITUITARY: • About the size of a kidney bean • Divided into three lobes: Anterior, posterior, intermediate

9. Anterior Pituitary Somatotropin = growth hormone (GH), stimulates protein synthesis, growth of muscle and bone • Deficit: midget • Excess: giantism (acromegaly) • Affects glucose metabolism; inhibits uptake and oxidation of glucose by cells, stimulates breakdown of fatty acid for energy (conserves glucose) Prolaction (PRL) –stimulates the secretion of milk in mammals • controlled by inhibiting hormone in hypothalamus • continued by nerve impulses from suckling; hypothalamus (supply upon demand)

10. Intermediate Pituitary Lobe • Melanocyte- stimulating Hormone (MSH) • (Wikipedia)  ...stimulate the production and release of melanin (melanogenesis) by melanocytes in skin and hair. • MSH is also produced by a subpopulation of neurons in the hypothalamus. • MSH released into the brain by these neurons has effects on appetite and sexual arousal. • More important for color change in reptiles, etc.

11. Posterior Pituitary Lobe • Hypothalamus releases Oxytocin and antidiuretic hormone (ADH) and stores it here, released by posterior pituitary • Oxytocin- "milk let down" hormone, stimulates uterine contractions, smooth muscle contraction (BP regulation) • Antidiuretic Hormone(ADH)- a.k.a. vasopression (increase BP) decreases excretion of water by kidneys. Increases permeability of water in nephrons

12. Regulation of The Other Glands: • Regulation: negative feedback system involving a gonadotropic (gonad-stimulating) hormone LH (luteinizing hormone): produced by ant. pituitary • In males: • LH is carried by blood to stimulate testes • as blood level of testosterone increases, LH production decreases • In females: • rise in LH stimulates ovulation FSH (follicle-stimulating hormone): • In males: acts upon the sertolicells of the testes, important for spermatogenesis • In females:  stimulates maturation of germ cells, sets mentrual cycle • High concentrations of LH cause germ cells to produce an inhibitor, "inhibin", which will then lower LH levels

13. The Endocrine Glands

14. Testes • Androgens- the "male sex hormones" • Testosterone (steroid) is one type.  Produced in the testes necessary for sperm production and secondary sex characteristics: • genitals • larnyx (voice change) • skeletal enlargement • muscle tissue • acne

15. The Ovaries • Estrogens- the "female sex hormones" • Different kinds of estrogen hormones:  estriol, estrone, and estradiol(most important) • Produced by ovaries by stimulation of FSH from pituitary • Stimulate development of secondary sex characteristics (breast development, genital development, distribution of body fat) • Progesterone- maintenance of pregnancy, uterus • (estrogen, progesterone interaction= menstrual cycle) • estrus cycle diagram, showing hormone fluctuations in the mare http://www.equine-reproduction.com/articles/estrous.htm

16. Prostaglandins • Hormone-like chemicals differ from other hormones: • Fatty acids (formed by oxygenation of Arachidonic Acid) • Produced by cell membranes of most organs (as opposed to specific glands) • Often exert effects on the tissues that produce them • The target tissue may be that of anotherperson (e.g. in semen, for fertilization) • More patent than hormones (needed in smaller amounts) • Effects- stimulation of smooth muscle (uterus- menstruation labor); blood vessel dilation/constriction (BP down, up); inflammatory response by T-cells

17. Adrenal Glands • Adrenal Cortex- outer layer of adrenal glands; major source of steroid hormones • Adrenal glands lie on top of kidneys ("ad-renal") • Humans: two major groups of adrenocortical steroids • Glucocorticoids • Mineralocorticoids

18. Adrenal Cortex: Glucocorticoids • Glucocorticoids- used to suppress inflammation (medical) • Cortisol- (most important) mainly the formation of glucose from fats and proteins. Inhibit up take of glucose by most cells (except brain and heart). Release increases during excitement etc.; work with sympathetic nervous system. • Secreted in response to AdrenocorticotropicHormone (ACTH), secreted by Ant. Pituitary ("master gland") which is stimulated by hormone released from Hypothalamus

19. Adrenal Cortex:Mineralocorticoids • Affect the ion concentration in the blood; water loss/retention. Aldosterone- (example) regulation of ions (K+, Na+) • Affect the transport of ions across membranes of the NEPHRONS • Deficiency leads to Na+ ion loss (via urine) = loss of water = lowers blood pressure • Since adrenal cortex is source of androgens (male and female) sex hormones, a tumor can increases male secondary sex characteristics (e.g. bearded ladies)

20. Adrenal Medulla • Central portion of adrenal made up of neurosecretory cells (rather than epithelial) • Adrenaline and Noradrenalin- increase rate and strength of heartbeat; raise BP; dilate resp. passages (act as enforcer of sympathetic N.S.)

21. PancreaticHormones: "Islets of Langerhans" • Insulin: secreted in response to rise in blood sugar or AA concentration. It lowers blood sugar by stimulating up take of glucose (conversion of glucose to glycogen by liver) • Glucagon: increases blood sugar by breakdown of glycogen glucose in liver and breakdown of fats/proteins • Somatostatin: synthesis of insulin • Five different sugar-regulating hormones (growth hormone, cortisol, insulin, adrenalin, glucagon) • Diabetes- insulin too low • Hypoglycemia- insulin too high http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter20/animation__blood_sugar_regulation_in_diabetics.html

22. Thyroid Gland: • Located on top of Larynx • Controlled by "hypothalamus- pituitary axis" - TSH (thyroid-stimulating hormones a.k.a. "thyrotropin" • A.  Thyroxine • Accelerates rate of cellular respiration (metabolism) • differs from androgens, estrogens, corticosteroids because it is an amino acid with 4 iodine atoms (T4), also T3 • B.  Calcitonin: inhibits release of calcium ions [Ca2+ ions] from bones. Secretion is controlled by Ca ion conc. in fluid around thyroid cells.

23. Thyroid diseases • Goiter is a swelling of the thyroid gland, results from low iodine in diet • Hyperthyroidism: (overproduction) weight loss, nervousness, fatigue.  Most common cause in Grave's Disease. • Hypothyroidism: (underproduction) dwarfism in infants (Cretinism) low energy, low brain cell development, can be caused by insufficient iodine in diet • autoimmune disease of thyroid :  Hashimoto's thyroiditis

24. Parathyroid Glands: • Located below thyroid, pea- size, smallest endocrine gland • Parathormone: essential in mineral metabolism, regulation of Calcium and Phosphate ions in blood • stimulates release of Ca?? ions from bones; secreted in response to low blood [Ca2+] • (Calcium = blood coagulation, muscle contraction, nerve function)

25. The Pineal Gland • Small lobe in forebrain, near center • Involved in "photoperiodism"- seasonal enlargement of ovaries etc. • Secretes hormone: Melatonin (up/down, day/night) • Melatonin: causes pigment cells to open/close "biological clock"