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IPHY 3430 10/27/11

IPHY 3430 10/27/11. Materials filtered into Bowman ’ s capsule Water Ions glucose, amino acids wastes (NH3, urea, etc) a few plasma proteins everything else in plasma hopefully no cells.

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IPHY 3430 10/27/11

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  1. IPHY 3430 10/27/11

  2. Materials filtered into Bowman’s capsuleWaterIonsglucose, amino acidswastes (NH3, urea, etc)a few plasma proteinseverything else in plasmahopefully no cells

  3. Tubular reabsorption involves transport of molecules in filtrate back into the blood.Passive diffusionActive transportPinocytosis

  4. Tubular ReabsorptionGlucose (cotransport with Na+; active)Amino Acids (cotransport with Na+; active)Na+ (active--about 67% reabsorbed in proximal tubule)All other positive ions (Ca++, K+, etc) activeSome negative ions (sulfate, phosphate)activeCl- passivewater--passive (by osmosis) following movement of other moleculesProteins = pinocytosisWastes = some urea diffuses back into blood

  5. Tubular reabsorptionExample: glucose (under 320 mg/ml filtered load) blood tubule All glucose restored to blood And none left in filtrate by end of proximal tubule None

  6. Tubular reabsorptionExample: glucose over 325 mg/min filtered load Carrier molecules for glucose saturated, so Some glucose left in filtrate by end of proximal tubule blood tubule Glucose left

  7. At the end of the proximal tubule:all glucose, amino acids, many ions except some of the Na+, Cl-, almost all protein, 65% of water, 50% urea have been reabsorbed back into blood Remaining in filtrate: about 35% of water, wastes, the rest of Na and Cl, excesses of any ions, toxins

  8. Loop of HenleSole purpose is to conserve waterDepends on an extracellular gradient of Na and Cl concentration

  9. Descending LoopPermeable to water filtrate Concentration of filtrate rises due to water leaving and concentrating solute 400 300 At bottom of Loop, another 15-20% of water reabsorbed back into blood 400 500 500 600 600 700 700 800 800 900 Direction of flow 1000 900 1000 1100 1100 1200 1200

  10. Ascending LoopNot permeable to waterConcentration of filtrate changes due to active transport of Na and Cl from filtrate filtrate 100 NaCl 200 400 600 NaCl Direction of flow 800 NaCl 1000 1200

  11. By the end of the loop of Henle, 15-20% more water reabsorbed back into bloodDistal tubuleActive secretion of K+ if necessaryActive secretion of H+ if necessary CO2 + H20 --> H2CO3--> H+ + HCO3- (carbonic anhydrase)

  12. Collecting DuctSecretes a variably concentrated urine depending on needs of the body filtrate filtrate 200 200 200 200 200 400 Overhydration: Minimal vasopressin secretion Dehydration: Maximal vasopressin secretion 600 200 800 200 1000 200 1200 1200 1200

  13. Regulation of body water (colloid osmotic pressure) cop --> hypothalamus--> posterior lobe of pituitary releases-->  vasopressin --> permeability of collecting duct to water-->  water reabsorption from filtrate into blood--> excretion of dilute, large volume urine -->  water content of blood -->  cop

  14. Regulation of body water (colloid osmotic pressure) cop --> hypothalamus--> posterior lobe of pituitary releases-->  vasopressin -->  permeability of collecting duct to water-->  water reabsorption from filtrate into blood--> excretion of concentrated, small volume urine -->  water content of blood --> cop

  15. Effect of alcohol on vasopressin secretion

  16. Renin-angiotensin system helps vasopressin conserve water, if necessary,for regulation of body water and blood pressure

  17. Angiotensin II also causes: aldosterone release from adrenal gland --->  Na+ uptake from urine -->  water uptake from urine -->  blood volume -->  venous return --> stroke volume -->  cardiac outputnet effect of  angiotensin II -->  BP

  18. Additional Na+ regulation blood Na+ --> adrenal gland-->  aldosterone secretion -->  active uptake of Na+ from filtrate in collecting duct -->  blood Na+and….

  19. Even more Na+ regulation blood Na+ --> heart atrium -->  secretion of atrial natriuretic peptide -->  absorption of Na+ from filtrate in collecting duct -->  blood Na+

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