2

• Low blood H2O level

  1. Pituitary gland secretes ADH

  2. ADH delivered to DCT

  3. DCT walls become permeable to water

  4. Water is reabsorbed into blood

  5. Concentration set by sodium pump

  6. Concentrated urine produced
• High blood H2O level

  1. Hypophysis stops ADH secretion

  2. DCT & collecting tubule become less permeable to water

  3. Less water reabsorbed

  4. Dilute urine produced
• Ionic / pH balance of blood

  • Blood is acidic -> excess Hydrogen ions
  • Blood is alkaline -> excess Bicarbonate ions
  • To maintain balance -> excess ions secreted then excreted
  • High acidity / low alkalinity -> H ions secreted by tubule walls into filtrate
  • Low acidity / high alkalinity -> Bicarbonate ions excreted by tubule walls into filtrate
• Aldosterone


  Secreted by adrenal cortex, function: regulate absorption / secretion of Na ions