Adrenal physiology (1)


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Adrenal physiology (1)

  1. 1. I. IntroductionI. Introduction Adrenal GlandsAdrenal Glands • suprarenal – they sit on top of the kidneys • each is composed of 2 distinct regions: A.A. Adrenal MedullaAdrenal Medulla - the inner region - comprises 20% of the gland - secretes epinephrine and norepinephrine - derived from ectoderm
  2. 2. B.B. AdrenalAdrenal CortexCortex • the outer regionthe outer region • comprises 80% of thecomprises 80% of the glandgland • secretes corticosteroidssecretes corticosteroids • derived from mesodermderived from mesoderm
  3. 3. 1) Zona Glomerulosa1) Zona Glomerulosa (outermost region)(outermost region) - produces mineralocorticoids (aldosterone) 2) Zona Fasiculata2) Zona Fasiculata (middle region)(middle region) - produces glucocorticoids (cortisol) as well as estrogens and androgens 3) Zona Reticularis3) Zona Reticularis (innermost region)(innermost region) - same function as zona fasiculata DHEA – dehydroepiandrosteroneDHEA – dehydroepiandrosterone • an adrenal androgen in females • responsible for growth of pubic and axillary hair
  4. 4. CC. Pathologies Associated with Adrenal. Pathologies Associated with Adrenal AndrogenAndrogen HypersecretionHypersecretion 1.1.Adrenogenital SyndromeAdrenogenital Syndrome - hypersecretion of androgens or estrogens- hypersecretion of androgens or estrogens a)a) in the adult femalein the adult female:: - masculinization (i.e. hirsutism)- masculinization (i.e. hirsutism) b)b) in the female embryoin the female embryo:: - female pseudohermaphroditism- female pseudohermaphroditism c)c) in the adult malein the adult male:: - no effect- no effect d)d) in young boysin young boys:: - precocious pseudopuberty- precocious pseudopuberty
  5. 5. II. MineralocorticoidsII. Mineralocorticoids (Aldosterone)(Aldosterone) A.A. FunctionsFunctions - promotes reabsorption of Na+ and secretion of K+ from the distal portion of the nephron B.B. Regulation of SecretionRegulation of Secretion 1. Renin Angiotensin - Angiotensin II stimulates aldosterone secretion 2. Potassium - high levels of K+ induce aldosterone secretion
  6. 6. C.C. PathologiesPathologies 1. Hypersecretion1. Hypersecretion a.a. primary hyperaldosteronismprimary hyperaldosteronism - Conn’s syndrome- Conn’s syndrome - usually due to a tumor on the gland- usually due to a tumor on the gland - too much secretion of gland itself- too much secretion of gland itself b.b. secondary hyperaldosteronismsecondary hyperaldosteronism - default in renin angiotensin system- default in renin angiotensin system - most common in atherosclerosis of- most common in atherosclerosis of renal arteriesrenal arteries 2. Hyposecretion (defer to2. Hyposecretion (defer to
  7. 7. III. GlucocorticoidsIII. Glucocorticoids (Cortisol)(Cortisol) A. Metabolic Effects - overall effect: increase plasma glucose levels, often at the expense of proteins and fats 1. CHO Metabolism a. gluconeogenesis cortisol helps convert skeletal muscle protein to CHO’s and eventually glycogen b. decrease glucose utilization(anti- insulin effect)
  8. 8. 2. Protein Metabolism2. Protein Metabolism - proteins are mobilized by cortisol to be converted to CHO’s in a fasting state - lean body mass decreases 3. Fat Metabolism3. Fat Metabolism - cortisol causes lipolysis (inhances catecholamines) - expectations: person will be thin, but if excessive cortisol see unusual fat distribution (i.e. “buffalo hump”) 4. Increases Hunger4. Increases Hunger
  9. 9. B. Other EffectsB. Other Effects 1.1. Fetal DevelopmentFetal Development • Cortisol aids in maturation of the lungs, especially with the production of surfactant • Maturation of g.i. enzymes
  10. 10. B. Other Effects AdultsB. Other Effects Adults 1.1. StressStress - Hans Selye: experimented by stressing animals - results: stress is associated with increased levels of glucocorticoids - explanation: glucocorticoids mobilize a pool of amino acids to construct needed proteins or enzymes to face the stress
  11. 11. B. Other Effects (cont.) 2. Anti-inflammatory - during tissue damage, phospholipase A2activity increases releasing arachadonic acid to aid in synthesis of prostaglandins & leukotrienes - glucocorticoids enhance production of macrocortin which inhibits phospholipase A2and thus the inflammatory response 3. Immune Response - glucocorticoids suppress the immune system by decreasing the number of T lymphocytes - used frequently after organ transports
  12. 12. B. Other Effects (cont.) 4. Vasoconstriction - Glucocorticoids necessary for vasocontriction effects of the catecholamines 5. Stimulates Erythropoietin 6. Increases Bone Reabsorbtion 7. Decreases REM Sleep
  13. 13. C. RegulationC. Regulation - it’s a classic negative feedback system - low glucocorticoid levels cause the hypothalamus to secrete corticotropin releasing hormone (CRH) - CRH and low glucocorticoid levels cause the anterior pituitary to release ACTH - ACTH stimulates glucocorticoid production at the adrenal cortex * Stress and hypoglycemia can also trigger the release of CRH
  14. 14. D.D. PathologiesPathologies 1)1) HypersecretionHypersecretion - Cushing’s Syndrome - caused by too much exogenogeous cortisol, too much ACTH, an adrenal tumor, or ACTH secreting tumor – Symptoms » Proteolysis » Moon-faced and buffalo hump
  15. 15. D.D. Pathologies CONT.Pathologies CONT. 2)2) HyposecretionHyposecretion a)a) Primary Adrenal CorticalPrimary Adrenal Cortical InsufficiencyInsufficiency - Addison’s Disease - due to autoimmuno destruction of the gland b)b) Secondary Adrenal CorticalSecondary Adrenal Cortical InsufficiencyInsufficiency - due to too little ACTH
  16. 16. EICOSANOIDSEICOSANOIDS ARACHIDONIC ACID prostaglandinsprostaglandins leukotriensleukotriens thromboxanesthromboxanes prostacyclinsprostacyclins
  17. 17. Prostaglandin Nomenclature •3 Groups •PGA •PGE •PGF •Double BondsDouble Bonds •Optical IsomerOptical Isomer
  18. 18. Prostaglandin Functions • Reproduction • Respiratory • Nervous • Immune • MANY OTHERS!!