Renal Phys 5

• average daily water gain and loss in adults 


  table:

  
• daily sodium chloride intake and output


  table:

  
• intake must equal output for ___________ to be maintained

  homeostasis
• _____ is the main regulator for intake to match output

  urine
• liter distribution between plasma, ISF, and ICF

  plasma - 3 L

  ISF - 11 L

  ICF - 28 L
• H2O distributes itself equally across all membranes; majority goes into cells
• NaCl stays in ECF; cells have pumps to pump NaCl out and H2O follows osmotically
• baroreceptors detect the pressure changes due to pure gains in NaCl
• osmoreceptors detect ECF osmolarity changes due to pure gains in water
• baroreceptors detect pressure changes in the ECF (not in ICF), pure gains in NaCl change ECF volume
• pure gains in water do not change ECF pressure much, but do change ECF osmolarity
• total-body NaCl is proportional to ECF volume and to blood pressure 


  image:
• freely filtered at the glomerulus, mostly reabsorbed, no secretion



  Na+ and H2O

  
• mechanism of Na+ reabsorption in the proximal tubule


  65% of Na+ reabsorption occurs here and is non-regulated

  
• mechanism of Na+ reabsorption in the ascending limb of the Loop of Henle


  - NKCC transporter in apical (luminal) membrane is critical here

  - 25% of Na+ reabsorption occurs here and in non-regulated

  
• mechanism of Na+ reabsorption in the cortical collecting duct


  Na+ reabsorption occurring here is regulated

  
• a steroid hormone from the zona glomerulosa of the adrenal cortex, builds more Na+ and K+ channels and Na+/K+ ATPases

  aldosterone
• an increase in aldosterone _________ sodium regulation and vice versa

  increases