1. GEORGE B. JOHNSON Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display PowerPoint ® Lectures prepared by Johnny El-Rady 24 Chemical Signaling Within the Animal Body Essentials of The Living World First Edition

2. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24.1 Hormones A hormone is a chemical signal that is produced in one part of the body and that acts at a distant site Three advantages to using chemical signals 1. Can spread to all tissues via the blood 2. Can persist much longer than electric signals 3. Many can act as hormones Different hormones can target different tissues

3. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Hormones are produced by endocrine glands These glands do not have ducts Hormones are secreted directly into the blood Hormones are under the control of the neuroendocrine system The hypothalamus is the main switchboard Issues commands to the nearby pituitary gland Pituitary sends chemical signals to the various hormone-producing glands in body

4. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.1 Major glands of the human endocrine system

5. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Hormones are effective because they are recognized by specific receptors These are on or in target cells The path of communication of a hormone signal 1. Issuing the command By the hypothalamus 2. Transporting the signal By the blood 3. Hitting the target Binding to the receptor 4. Having an effect A change in cell activity

6. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.2 How hormonal communication works

7. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24.2 How Hormones Target Cells Steroid hormones Manufactured from cholesterol Lipid-soluble and thus can across the lipid bilayer of the cell membrane Bind to receptors within the nucleus usually The hormone-receptor complex binds to DNA causing changes in gene activity Anabolic steroids Synthetic compounds resembling testosterone Cause muscle cells to produce more protein

8. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.3 How steroid hormones work

9. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Peptide hormones Short peptides or full-sized proteins Bind to receptors embedded in the cell membrane Induce a change in cytoplasmic end of the receptor protein Triggers events within the cytoplasm Fig. 24.4

10. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The change in cellular activity is facilitated by second messengers such as cAMP Trigger a cascade of enzymic activation within cell Fig. 24.5

11. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24.3 The Hypothalamus and the Pituitary The pituitary gland is located in a bony recess in the brain below the hypothalamus It produces nine major hormones It is actually two glands Posterior lobe Anterior lobe

12. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Stores and releases two short peptide hormones Vasopressin (antidiuretic hormone, ADH) Regulates water conservation by the kidney Oxytocin Initiates uterine contractions during childbirth Causes milk letdown Both synthesized within hypothalamus neurons Transported down nerve axons to the posterior lobe The Posterior Pituitary

13. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.6 Posterior pituitary

14. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display A complete gland that produces seven major hormones 1. Thyroid-stimulating hormone (TSH) 2. Luteinizing hormone (LH) 3. Follicle-stimulating hormone (FSH) 4. Adrenocorticotropic hormone (ACTH) 5. Growth hormone (GH) 6. Prolactin 7. Melanocyte-stimulating hormone (MSH) The Anterior Pituitary

15. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.7 The role of the pituitary

16. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The hypothalamus controls the anterior pituitary Fig. 24.8 Secretes releasing and inhibiting hormones into capillaries Hypothalamo- hypophyseal portal system carries the hormones to the pituitary

17. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.9 Hypothalamus and anterior pituitary are themselves controlled by negative feedback inhibition Regulated by the hormones whose secretion they stimulate! Thyrotropin- releasing hormone Corticotropin- releasing hormone Gonadotropin- releasing hormone

18. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24.4 The Pancreas The pancreas gland is located behind the stomach Secretes a number of digestive enzymes into the small intestine through a narrow tube Islets of Langerhans govern blood glucose levels Insulin Secreted by beta cells Storage hormone that promotes accumulation of glycogen in liver and triglycerides in fat cells Glucagon Secreted by alpha cells Cause release of stored glucose and fat breakdown

19. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.10

20. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Diabetes mellitus Affected individuals cannot take up glucose from the blood Type I ~ 5-10% of diabetics Autoimmune disorder in which immune systems attacks the Islets of Langerhans Develops before age 20 (juvenile-onset diabetes) Treated by daily injections of insulin Type II ~ 90-95% of diabetics Caused by abnormally low number of insulin receptors Develops after age 40 (adult-onset diabetes) Typically in obese individuals Treated by diet and exercise

21. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24.5 The Thyroid, Parathyroid and Adrenal Glands The thyroid gland lies just below the Adam’s apple in front of the neck Its two most important hormones are Thyroxine Increases metabolic rate and promotes growth Contains iodine Lack of iodine in diet causes goiters Calcitonin Stimulates calcium deposition in the bone

22. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.11 The thyroid gland secretes thyroxine Goiter

23. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The parathyroid glands are four small glands attached to the thyroid Produce parathyroid hormone (PTH) One of only two hormones essential for survival Acts as a fail-safe mechanism ensuring that calcium levels never fall too low Calcium ions are key to muscle contractions When levels are low, PTH stimulates osteoclast cells to break down bone matrix This raises calcium levels in the blood PTH also acts on kidneys to reabsorb calcium ions from the urine

24. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.12 Maintenance of proper calcium levels in the blood

25. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The adrenal glands are two glands, one located just above each kidney Each composed of two parts Medulla – Inner core Adrenaline and norepinephrine Released in times of stress to stimulate rapid deployment of body fuel Cortex – Outer shell Cortisol – Stimulates carbohydrate metabolism and reduces inflammation Aldosterone – Stimulates the kidney to uptake sodium and other ions from the urine This is the other hormone that is absolutely essential for survival

26. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24.6 A Host of Other Hormones Steroid sex hormones Estrogen, progesterone and testosterone Produced by gonads to regulate sexual development Atrial natriuretic hormone Secreted by the right atrium of the heart Stimulate kidneys to excrete salts and water in the urine Erythropoietin Secreted by the kidney Stimulates the bone marrow to produce RBC

27. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Molting is triggered by the molting hormone, also called ecdysone The production of ecdysone is itself controlled by the brain hormone These two hormones are balanced by a third hormone, the juvenile hormone If present in high levels, it inhibits the formation of the pupa and adult forms Molting and Metamorphosis in Insects

28. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig. 24.13 The hormonal control of metamorphosis in the silkworm moth, Bombyx mori