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Chapter 16 - Endocrine System Lecture 16

Martini’s Visual Anatomy and Physiology First Edition Martini w Ober. Chapter 16 - Endocrine System Lecture 16. Lecture Overview. The Adrenal Glands The Pancreas Other Endocrine Tissues Stress and its effects Life-span changes. Location/Blood Supply of the Adrenal.

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Chapter 16 - Endocrine System Lecture 16

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  1. Martini’s Visual Anatomy and Physiology First Edition Martini w Ober Chapter 16 - Endocrine System Lecture 16

  2. Lecture Overview • The Adrenal Glands • The Pancreas • Other Endocrine Tissues • Stress and its effects • Life-span changes

  3. Location/Blood Supply of the Adrenal Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

  4. Adrenal Glands Figure from: Hole’s Human A&P, 12th edition, 2010 Adrenal cortex and medulla are functionally distinct

  5. Hormones of the Adrenal Medulla • Epinephrine (80%)and Norepinephrine (20%) • derived from amino acid tyrosine • hormones of ‘fight or flight’ are called catecholamines • release controlled by sympathetic nervous system (neural control of hormone release) • hormone releasing cells are considered equivalent to postganglionic sympathetic neurons • increases heart rate and blood pressure • dilates respiratory airways • promotes glycogenolysis and gluconeogenesis • activates reticular formation • increases metabolic rates

  6. Adrenal Cortex and its Hormones • Yellowish appearance of cortex is due to stored lipids, especially cholesterol and various fatty acids • Produces more than 25 steroid hormones • Hormones of the Adrenal Cortex are… • Called adrenocortical steroids, or corticosteroids • Carried in blood bytranscortins • Essential to life • Affect cellular metabolism by determining the nature and concentration of cellular enzymes • Not stored in cell

  7. Adrenocortical Steroids - Aldosterone • increases blood volume and pressure by promoting conservation of sodium ions and water (distal tubules of kidney) • Activated by 1) the renin-angiotensin system and by 2) changing concentrations of of Na+ and K+ • Zona glomerulosa Figure from: Hole’s Human A&P, 12th edition, 2010 Aldosterone is a mineralocorticoid

  8. Adrenocortical Steroids - Glucocorticoids • Cortisol (hydrocortisone) – a glucocorticoid •  protein synthesis,  protein catabolism • increases fatty acid release (glucose-sparing effect) • stimulates gluconeogenesis • controlled by CRH from hypothalamus and ACTH from anterior pituitary Produced in the Zona Fasciculata Blood levels peak shortly after arising in morning Have anti-inflammatory and anti-immune effects Figure from: Hole’s Human A&P, 12th edition, 2010

  9. Adrenocortical Steroids - Androgens • Adrenal androgens (gonadocorticoids) • supplement sex hormones from the gonads (release stimulated slightly by ACTH; inhibitory stimulus unknown). Mostly dehydroepiandrosterone (DHEA) • may be converted to estrogen in the blood (♀) • When secreted in normal amounts, neither adrenal androgens or estrogens affect sexual characteristics (may affect sex drive in ♀) • Produced in the Zona Reticularis • Tumors of this region can lead to androgenital syndrome (masculinization)

  10. Endocrine Pancreas Figures from: Hole’s Human A&P, 12th edition, 2010

  11. Cells of the Pancreatic Islets • Alpha cells - Glucagon • Beta cells – Insulin,amylin • Delta cells • Somatostatin (growth hormone-inhibiting hormone, GH-IH) • Suppresses release of insulin and glucagon • Slows rates of food absorption • F cells • Pancreatic polypeptide (inhibits GB contractions – exact physiological role is uncertain)

  12. Insulin Insulin decreases blood glucose levels by allowing cells to take up glucose from the blood Binding enhances glucose uptake Brain, kidneys, liver, RBCs are insulin independent Insulin release is also affected by the ANS Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

  13. Glucagon Raises blood glucose levels by: - stimulating breakdown of stored molecules- increasing release and formation of glucose Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

  14. Insulin and Glucagon Figure from: Hole’s Human A&P, 12th edition, 2010 Example of a humoral stimulus for hormone secretion

  15. Pineal Gland Pinealocytes synthesize melatonin from serotonin

  16. Melatonin • regulates circadian rhythms - daily changes in physiological processes that follow a regular pattern • Light (eyes) → retina → hypothalamus → reticular formation  •  melatonin  pineal  sympathetic fibers  spinal cord • may control onset of puberty (melatonin levels decline at puberty) • helps regulate female reproductive cycle • may protect CNS against free radicals (antioxidant)

  17. Other Endocrine Glands • Reproductive Glands • ovaries secrete estrogen and progesterone • testes secrete testosterone • placenta secretes estrogen, progesterone, and gonadotropins, e.g., hCG • Thymus Gland • secretes thymosins • promotes development of T-lymphocytes • Heart • secretes natriuretic peptides(ANP, BNP) • - Natri = sodium; uretic = in the urine • promote loss of water and Na+ at the kidney • secreted when atria/ventricles are stretched • - inhibit renin release • - inhibit secretion of ADH and aldosterone

  18. Stress • Types of Stress • physical stress • psychological (emotional) stress • (Stress is any condition, physical or emotional, that threatens homeostasis) • Stress Response (General Adaptation Syndrome [GAS]) • hypothalamus triggers sympathetic impulses to various organs • epinephrine is released • cortisol is released to promote longer-term responses • Three general phases of the GAS in response to stress ARE: • Alarm phase • Resistance phase • Exhaustion phase

  19. Responses to Stress Exhaustion -  lipid reserves - production of glucocorticoids - electrolyte imbalance - damage to vital organs Figure from: Hole’s Human A&P, 12th edition, 2010

  20. GH Abnormalities Figure from: Hole’s Human A&P, 12th edition, 2010 Growth Hormone Ups and Downs • Gigantism - hypersecretion of GH in children • Acromegaly – hypersecretion of GH in adults • Dwarfism – hyposecretion of GH in children Age 9 Age 16 Age 33 Age 52

  21. Diabetes (= Overflow) • Diabetes Mellitus (DM) • Hyposecretion or hypoactivity of insulin • Three P’s of Diabetes Mellitus (mellitum = honey) • Polyuria (increased urination) • Polydipsia (increased thirst) • Polyphagia (increased hunger) • Hyperglycemia, ketonuria, glycosuria • Renal Glycosuria • excretion of glucose in the urine in detectable amounts • normal blood glucose concentrations or absence of hyperglycemia • Diabetes Insipidus (insipidus = tasteless) • Hyposecretion or hypoactivity of ADH • Polyuria • Polydipsia

  22. Hormone Summary Table I Se(x) T G A P

  23. Hormone Summary Table II

  24. Review • Reaction to stress occurs in three stages • Short term • Alarm or “fight or flight” • Reactions similar to sympathetic stimulation • Mediated by hormones of the adrenal medulla • Long term • Resistance • Long-term raising of blood glucose • Mediated by hormones of the adrenal cortex • Exhaustion • Failure of compensatory mechanisms

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