Acid-Base Balance
Terms
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What is the typical pH in the body?
What MUST it stay between? -
7.4 -> (- log 40nM)
Must be btwn 6.8 - 7.8 to sustain life. -
What is the ECF concentratino of
-Acid
-Sodium -
H+ is 40 nM - nano
Sodium is 150 mM - milli - What is the purpose of having acid in the ECF?
- to regulate enzymes and their receptors.
- By what 4 ways is H+ produced in the body?
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1. Co2 rxtn with H2o
2. Anaerobic Glucose metabolism.
3. Fatty acid metabolism
4. Protein metabolism. - What acid each process produce?
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Carbon Dioxide = H3O+
Anaerobic Glucose mtbm = Lactic Acid
Fatty aa. mtbm = ketone body acids.
Protein = HCL/H2SO4 -
What type of diets produce
-Net base
-Net Acid -
Mixed diet -> net Acid.
Vegetarian -> net Base. - What 3 process regulate body pH?
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1. Buffers
2. Respiratory system
3. Renal system - How fast do buffers respond to pH changes?
- within SECONDS - fast.
- What are the 3 main buffer systems in the body?
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1. Phosphate
2. Proteins (hemoglobin)
3. Bicarbonate system. - Which buffer is an open system?
- Bicarbonate - the individual species can be removed/added from the body.
- How soon does the respiratory system respond to pH changes?
- within Minutes.
- How does the respiratory system regulate pH?
- When pH is decreased (more acid), respiration increases in order to decrease CO2, shifting the equilibrium to LEFT and removing H+.
- How soon does the renal system respond to changes in pH?
- within DAYS - slowest.
- How does the renal system respond? (2 major things)
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1. Excretes H+
2. Reabsorbs or creates HCO3- - what nephron cells respond mostly to H+ increase? How?
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PCT - prox tubule cells.
-Glutamine breaks into NH4+ and HCO3-. Ammonium gets excreted, Bicarbonate reabsorbed into blood as a buffer. - How does Bicarbonate in PCT cells normally get rid of H+?
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1. CO2 diffuses from tubule lumen into PCT cells, Reacts with H2o and forms H2CO3.
2. Carbonic aa. then breaks into Bicarbonate and H+.
3. H+ exchanges for Na+ from lumen, and Bicarbonate is reabsorbed to blood. - So how does HCO3- production from Glutamine breakdown help get rid of H+?
- It combines with excess H+ and acts as a buffer.
- Is acid excreted in urine to no end?
- No - the limit is pH of 4.5
- How is acid excretion limited?
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By the phosphate buffer system.
HPO42- filters at glomerulus; forms H2PO4- to prevent hyperacidic urine. - What are the 4 terms for disturbed acid-base balance?
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1. Respiratory acidosis
2. Respiratory alkalosis
3. Metabolic acidosis
4. Metabolic alkalosis - IF YOU KNOW NOTHING ELSE, WHAT DISTINGUISHES RESP ACIDOSIS?
- High Co2 levels.
- What disease causes respiratory acidosis?
- Decreased ventilation from severe asthma (results in high CO2 levels)
- How does the patient compensate for respiratory acidosis?
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With the renal system, by producing HCo3- to buffer:
-More H+ secretion
-More HCO3- reaborption - What is the primary cause of Respiratory alkalosis?
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Decreased CO2 levels, due to -high altitudes
-increased ventilation. - How is respiratory alkalosis compensated for?
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With the renal system;
-Less H+ secretion
-Less HCO3- reabsorption. - What's the disadvantage of how respiratory acidosis/alkalosis are compensated?
- It takes days so you feel bad for a few days before getting better.
- What is metabolic acidosis ALWAYS ASSOCIATED WITH?
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Decreased HCO3- due to
-Loss of HCO3- OR
-Addition of H+ - What are 3 causes metabolic acidosis?
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1. Kidney failure (no HCO3- reabsorption)
2. Diarrhea (lose alk fluid)
3. Exercise (lactic acid) - How does the body compensate for metabolic acidosis?
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By breathing more - fast response w/in minutes.
Incr. ventilation decreases CO2 and H+. - What is the main problem in metabolic alkalosis?
- High HCO3- or loss of H+.
- What are 2 causes of metabolic alkalosis?
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1. Antacid abuse
2. Vomiting - how does the body compensate for metabolic alkalosis?
- by less respiration - decresaed ventilation increases CO2 and H+.
- How do you distinguish in all these cases?
- by measuring Co2 and HCO3- levels,NOT PH.