Endocrine System

1. Endocrine System Modified from: http://www2.kumc.edu/instruction/nursing/nrsg812/endocrine/ Images from: http://www.endocrineweb.com/ gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookENDOCR.html

2. Mechanisms of Hormone Action • Certain secretory cells release chemical agents (hormones) for the purpose of mediating biologic responses in distant Target Cells. • Hormones sources • Single amino acid (catecholamines) • Chains amino acids (peptide hormones of hypothalamus) • Cholesterol (steroids)

3. Mechanisms of Hormone Action • Hormones control and integrate many body functions with this system. • In general, hormonal control regulates the metabolic functions of the body, the types of effects that occur inside the cell and determined the character of the cell itself. • The endocrine system works with the nervous system to regulate: metabolism, water and salt balance, blood pressure, response to stress, and sexual reproduction.

4. 3 Forms of Hormonal Communication 1. Endocrine = hormones are secreted into blood to regulate the function of distant target cell 2. Paracrine = endocrine cells secrete into surrounding extracellular space. Target cells are neighbors 3. Neuroendocrine = Directly into blood (norepin), & into brain interstitial space (Vasopressin)

5. Endocrine System • Endocrine System Hormones/Glands whose functions are solely endocrine include: • pituitary (hypophysis) • pineal • thyroid • parathyroids • adrenals • pancreas

6. Hypothalamus and Pituitary • Pituitary has direct neural and blood connection to the hypothalamus • Hypothalamus sends releasing factors to anterior pituitary • Hypothalamus stimulates posterior pituitary via neural pathway

7. Hypothalamus • Hypothalamus can synthesize and release hormones from its axon terminals into the blood circulation. • controls pituitary function and thus has an important, indirect influence on the other glands of the endocrine system. • exerts direct control over both the anterior and posterior portions of the pituitary gland. • regulates pituitary activity through two pathways: a neural pathway and a portal venous pathway.

8. Hypothalamus • Neural pathways extend from the hypothalamus to the posterior pituitary lobe, where the hormones are stored and secreted. • Portal venous pathways connect the hypothalamus to the anterior pituitary lobe, carry releasing and inhibiting hormones

9. Pituitary Gland • Pituitary Gland is located at the base of the skull in an indentation of the sphenoid bone. • Is joined to the hypothalamus by the pituitary stalk (neurohypophyseal tract) and consists of the anterior pituitary and the posterior pituitary

10. Anterior pituitary gland (adenohypophysis) • Called the master gland, because its anterior lobe has direct control over the secretion of: • ADH - antidiuretic hormone (vasopressin) • ACTH - adrenocorticotrophic hormone • TTH - thyrotrophic hormone • GH - growth hormone • FSH - follicle stimulating hormone • LH - leutinizing hormone

11. Posterior pituitary • Stores and secretes hormones made in the hypothalamus and contains many nerve fibers. • ADH (Antidiuretic Hormone/Vasopressin), which controls the rate of water excretion into the urine • Regulates Na+ & K+ reabsorption in the kidneys this influences blood volume & blood pressure • Oxytocin, which, among other functions, helps deliver milk from the glands of the breast.

12. Adrenal Glands • Adrenal Glands have an outer cortex and an inner medulla. • The adrenal cortex and medulla are major factors in the body's response to stress.

13. Kidneys—Renal Hormones • Renin is an hormone/enzyme (released from juxtaglomerular cells)

14. Thyroid Gland • Thyroid function is regulated by the hypothalamus and pituitary, feedback controls an intrinsic regulator mechanism

15. Thyroid Problems • Thyroid gland enlargement may or may not be associated with abnormal hormone secretion. • An enlarged thyroid gland can be the result of: • iodine deficiency (Goiter) • inflammation, or • benign or malignant tumors

16. Parathyroid Glands • There are 4 parathyroid glands located behind the thyroid. • Parathyroid Glands are important in calcium metabolism phosphorus metabolism

17. Pancreas • endocrine gland, secreting the hormones insulin and glucagon, exocrine gland, producing digestive enzymes. • Secretes insulin, glucagon (regulate blood sugar)

18. Cellular Mechanisms of Hormone Action • Hormonal interaction with target cells begin withreversible binding to specific receptors 1. Interactions with membrane receptor (protein) 2. Interactions with nuclear receptors (steroid)

19. Amino Acid Based Hormones • Bind to receptor sites on cell membranes • Amino acid hormone binding causes changes to occur receptor can activate carrier molecules which transport substances across the membrane • receptor can activate second messengers

20. Second Messengers • Second Messengers set a series of reactions in motion • Activate adenylate cyclase, generates cAMP from ATP • cAMP activates other proteins within the cell increases glycogenolysis & lipolysis • Open Ca2+ ion channels, activates calmodulin • Hydrolyzes phospholipase C into inositol triphosphate & diacylglycerol

22. Steroid Hormones • Steroid hormones are produced by chemical modification of cholesterol • Major classes steroid hormones • glucocorticoids (cortisol) • mineralocorticoids (aldosterone) • androgens (testosterone) • estrogens (estradiol) • Vitamin D metabolites

23. Steroid Hormones • Diffuse into cell and influence DNA • Bind to a protein associated with DNA • Cause DNA to increase synthesis of specific amino acids

24. Feedback Loops • The release of a hormone is often triggered by a change in the concentration of some substance in the body fluids. • Each hormone has a corrective effect, eliminating the stimulus, which then leads to a reduction in hormone secretion. • This process is called a negative feedback homeostatic control system to keep hormones at normal levels. (if levels increased it would be called positive feedback)

25. Blood Sugar Control • Insulin and glucagon are produced by small groups of cells in the pancreas (islets of Langerhans). • Beta cell make insulin (beta cells) and Alpha cells that make glucagon • Insulin is released when the blood sugar rises too high. Insulin tells the cells to use sugar. • Glucagon is produced when the blood sugar is falling too low. Glucagon tells the liver to release sugar that was stored there when the blood sugar was higher.