997399 adrenal-glands

Click here to load reader

download 997399 adrenal-glands

of 17

  • date post

    23-Dec-2014
  • Category

    Documents

  • view

    385
  • download

    1

Embed Size (px)

description

 

Transcript of 997399 adrenal-glands

  • 1. www.Examville.com Online practice tests, live classes, tutoring, study guides Q&A, premium content and more .

2. THE ADRENAL GLANDS 3. They lie at the superior poles of the two kidneys. Each gland is composed of twodistinct parts:

      • 1.Adrenal Cortex 80%
  • 2.Adrenal Medulla- 20%

4. CORTICOSTERIODS group of hormones secreted by the adrenal cortex. These are synthesized from the steroidCholesterol . The following are the ADRENOCORTICAL HORMONES: 1.Mineralocorticoids affect electrolytes of the ECF Sodiumand Potassium2.Glucocorticoids Exhibit an important effect in increasing blood glucose concentration 3.Androgenic hormonesALDOSTERONE principal mineralocorticoid CORTISOL principal glucocorticoid 5. LAYERS OF ADRENAL CORTEX AND SECRETION 6. 1.Zona Glomerulosa -constitutes about15%of the adrenal cortex - cells are the only ones secreting Aldosterone -they contain enzynealdosterone synthase necessary for synthesis of aldosterone -secretion is controlled by ECF conc. ofAngiotensin IIandPotassium 7.

  • 2. Zona Fasciculata
  • -constitutes about75%of the adrenal cortex
  • - middle and widest layer
  • -secretes the glucocorticoidscortisolandcorticosteroneand small amounts ofadrenal androgensandestrogens
  • -secretion is controlled byhypothalamic- pituitary axisviaadrenocorticotropichormone (ACTH )

8.

  • 3. Zona Reticularis
  • -secretes the adrenal androgenhydroepiandrosterone(DHEA)andandrostenedioneand smallamounts ofestrogenand someglucocorticoids
  • -secretion is regulated byACTH and other factorsuch ascortical androgen-stimulatinghormonefrom the pituitary

9. 10. More Important Glucocorticoid Hormones including Synthetic ones:

  • 1. Mineralocorticoids
  • - Aldosterone( very potent , accounts for90%of allmineralocorticoid activity
  • -Desoxycorticosterone( 1/30as potent as aldosterone, but verysmall quantities secreted
  • -Corticosterone( slight minralocorticoid activity )
  • -9a-Fluococortisol( synthetic , slightly more potent thanaldosterone)
  • -Cortisol(very slight mineralocorticoid activity, but largequantity secreted
  • -Cortisone( synthetic , slight mineralocorticoid activity)

11.

  • 2.Glucocorticoid
  • - Cortisol( very potent , accounts for about95%of allglucocorticoid activity
  • - Corticosterone(provides4%of totalglucocorticoid) activity, much less potent thancortisol)
  • -Cortisone( synthetic , almost as potent as cortisol)
  • -Prednisone( synthetic , four times as potent as cortisol)
  • -Methyprednisone( synthetic,five tmes as potent ascortisol)
  • -D examethasone( synthetic , 30 times as potent ascortisol)

12. The Intense Glucocorticoid Activity of Dexamethasone, has almost zero mineralocorticoid activity, thus is important drug for stimulating specific glucocorticoid activity 13. FUNCTIONS OF MINERALOCORTICOID Aldosterone

  • 1 .Renal and Circulatory Effects of Aldosterone
  • a. Aldosterone Increases Renal Tubular Reabsorptionof Sodium and Secretion of Potassium especially in theprincipal cells of the collectingtubules , and to lesser extent in thedistal tubules andcollecting ducts
  • b. Excess Aldosterone Increases ECF Volume andArterial Pressure but Has Only a Small Effecton Plasma Sodium Concentration
  • c.Excess Aldosterone Causes Hypokalemia and MuscleWeakness; Too little Aldosterone CausesHyperkalemia and Cardiac Toxicity

14.

      • Hypokalemia causes severe muscle weaknesscaused by alteration of the electrical excitability of the nerve and muscle fiber membranes which prevents transmission of normal action potential
      • Deficient Aldosterone results tocardiac toxicity , includingweakness of heart contractionand development ofarrhythmia

15.

  • C. Excess Aldosterone Increases Tubular Hydrogen Ion
  • Secretion with Resultant Mild Alkalosis
      • -secretion hydrogen ion in exchange for sodium in theintercalated cells of the cortical collecting tubules
      • 2.Aldosterone Stimulates sodium and PotassiumTransport in Sweat Glands, Salivary Glandsand Intestinal Epithelial Cells
        • - same effects as it has on the renal tubules

16. Cellular Mechanism of Aldosterone Action

  • 1.Aldosterone diffuses readily to the interior of thetubular epithelial cells
  • 2.In the cytoplasm of the tubular cells, aldosterone combineswith specificcytoplasmic receptor protein
  • 3.Aldosterone-receptor complex diffuses into the nucleus,inducing RNA to form messenger RNA
  • 4.The mRNA diffuses back into the cytoplasm operating inconjunction with the ribosomes causes proteinformation

17. Its FREE to join. http://www.examville.com