1. The Endocrine System Chapter 15

2. Hormones Secreted by endocrine glands, endocrine cells, and certain neurons Travel through the bloodstream to nonadjacent target cells

3. Other Signaling Molecules Neurotransmitters Local signaling molecules Pheromones

4. Discovery of Hormones Bayliss and Starling severed nerves to dog’s intestine; left blood vessels intact Pancreas still responded Extracts of glandular epithelium also provoked pancreatic response Extracts contained secretin

5. Hormone Interactions Opposing interaction Synergistic interaction Permissive interaction

6. Endocrine System Main Sources Pituitary gland Adrenal glands Thyroid gland Parathyroid glands Pineal gland Thymus gland

7. Responses to Hormones Vary Different hormones activate different responses in the same target cell Not all types of cells respond to a particular hormone

8. Two Main Hormone Types Steroid hormones –Derived from cholesterol –Estrogens, progestins, androgens (such as testosterone), cortisol, aldosterone Peptide hormones –Peptides, proteins, or glycoproteins –Glucagon, ADH, oxytocin, TRH, insulin, somatotropin, prolactin, FSH, LH, TSH

9. Steroid Hormones receptor hormone-receptor complex gene product hormone Most diffuse across the plasma membrane and bind to a receptor Hormone-receptor complex acts in nucleus to inhibit or enhance transcription

10. Protein Hormone Hormone binds to a receptor at cell surface Binding triggers a change in activity of enzymes inside the cell glucagon receptor cyclic AMP+ P i ATP cAMP activates protein kinase A glucagon Protein kinase A converts phosphorylase kinase to active form and inhibits an enzyme required for glucagon synthesis.

11. The Hypothalamus Region in the forebrain Contains hormone- secreting cells Interacts with pituitary hypothalamus pituitary gland

12. Pituitary Gland Pea-sized gland at base of hypothalamus Two lobes –Posterior lobe stores and secretes hormones that were synthesized in the hypothalamus –Anterior lobe produces and secretes its own hormones

13. Posterior Lobe Antidiuretic hormone (ADH) Oxytocin (OCT) cell body in hypothalamus axons to the general circulation

14. Anterior Pituitary ACTH TSH FSH LH PRL STH

15. Normal Hormone Production Generally, the body produces only very small amounts of hormones To isolate 1 milligram of TRH, researchers dissected 7 metric tons of hypothalamic tissue

16. Abnormal Somatotropin Output Gigantism Pituitary dwarfism Acromegaly

17. Feedback Mechanisms Negative feedback –An increase in concentration of a hormone triggers activities that inhibit further secretion Positive feedback –An increase in concentration of a hormone triggers activities that stimulate further secretion

18. Cortisol Cortisol secretion –Inhibits blood glucose uptake by muscle and other tissues –Causes breakdown of proteins to amino acids and conversion to glucose –Causes degradation of adipose tissue to fatty acids for use as energy source

19. Feedback Control of Cortisol Secretion Hypothalamus senses rise in glucose and secretes less releasing hormone (CRH) Anterior pituitary responds by secreting less ACTH Adrenal cortex slows its secretion of cortisol

20. Localized Feedback in Adrenal Medulla Norepinephrine secreted by neurons in the medulla accumulates in the synaptic gap Some molecules bind to receptors on the axon endings that secreted them This prevents further secretion of norepinephrine by that axon

21. Thyroid Gland Disorders Goiter Hyperthyroidism Hypothyroidism

22. Calcium Regulation Parathyroid hormone (PTH) is the main regulator of calcium in the blood It is secreted when calcium levels drop PTH causes bone cells to digest bone tissue and release calcium PTH also stimulates calcium reabsorption by the kidneys and absorption by the gut

23. Control of Glucose Metabolism insulin Glucose rises Glucose falls Glucose is absorbed Cells use glucose glucagon Glycogen to glucose Glucose uptake Glucose to glycogen

24. Diabetes Mellitus Disease in which excess glucose accumulates in blood, then urine Effects include –Excessive urination –Constant thirst –Weight loss –Ketone formation and acid-base imbalances

25. Two Types of Diabetes Type 1 Autoimmune disease Usually appears in childhood Treated with insulin injections Type 2 Target cells don’t respond Usually appears in adults Treated with diet, drugs

26. The Pineal Gland Photosensitive gland embedded in brain In the absence of light, secretes melatonin Affects the human biological clock May also play a role in human puberty and in seasonal affective disorder

27. Local Signaling Molecules Prostaglandins –Produced and secreted in response to local changes –Sixteen types with a variety of effects Growth factors –Affect cell division rates in tissues