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Physiology 3120 Lecture Notes - Respiratory Alkalosis, Respiratory Acidosis, Metabolic Alkalosis

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Tom Stavraky

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Human Physiology
Wednesday, December 9, 2009
“Renal VIII”
Acid/Base Balance
Collecting duct is the region of the nephron for this
Hydrogen or bicarbonate will be secreted into the filtrate
Two types of CD cells
Type A intercalated cells H+ secretors
CO2 and water combine (with carbonic anhydrase) to produce hydrogen & bicarbonate
These cells use a H+ ATPase to pump H+ into filtrate
Bicarbonate is reabsorbed using a bicarbonate-chloride antiporter; also have a chloride
channel on luminal membrane to secrete excess Cl
Also use K/H ATPase
Type B intercalated cells HCO3 secretors
CO2 transport occurs more on basolateral side where the blood is
Same step to produce hydrogen and bicarbonate
Same antiporter as before, but this time it’s on the luminal membrane; same Cl channel
on opposite membrane as well (basolateral)
Hydrogen pumped out with ATPase and K/H ATPase
Causes of acid/base disturbances
1. Metabolic acidosis (excess acid)
Excessive breakdown of fats or certain amino acids
Ingestion of aspirin, methanol, or antifreeze
2. Respiratory acidosis
Not being able to expel CO2 properly (hypoventilation)
Don’t get enough air, or respiratory depression
3. Metabolic alkalosis
Excessive loss of H ions due to vomiting
Ingestion of bicarbonate-containing antacids
4. Respiratory alkalosis
Too much CO2 (hyperventilation)
Kidney symptoms & diseases
1. Diabetes mellitus
Sugar diabetes
Body can’t reabsorb glucose sufficiently
Excess glucose load is filtered into Bowman’s space and excreted in urine
Na/glucose symporter unable to reabsorb all glucose sufficiently (limited capacity
because facilitated diffusion)
2. Diabetes insipidus
Lack of ADH production (neurogenic DI), or tubule response to ADH (nephrogenic DI)
Excessive dilute urine because of decreased water reabsorption
Pathology of the kidney
When kidney can’t regulate homeostasis, use procedures such as. . .
1. Hemodialysis
Blood pumped through a dialyzer (2 compartments separated by semi-permeable
Solution (dialysate) is pumped through the other compartment in the opposite
direction (countercurrent)
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