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Acid-Base Balance


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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
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?
1. Co2 rxtn with H2o
2. Anaerobic Glucose metabolism.
3. Fatty acid metabolism
4. Protein metabolism.
What acid each process produce?
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?
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?
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)
1. Excretes H+
2. Reabsorbs or creates HCO3-
what nephron cells respond mostly to H+ increase? How?
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+?
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?
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?
1. Respiratory acidosis
2. Respiratory alkalosis
3. Metabolic acidosis
4. Metabolic alkalosis
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?
With the renal system, by producing HCo3- to buffer:
-More H+ secretion
-More HCO3- reaborption
What is the primary cause of Respiratory alkalosis?
Decreased CO2 levels, due to -high altitudes
-increased ventilation.
How is respiratory alkalosis compensated for?
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?
Decreased HCO3- due to
-Loss of HCO3- OR
-Addition of H+
What are 3 causes metabolic acidosis?
1. Kidney failure (no HCO3- reabsorption)
2. Diarrhea (lose alk fluid)
3. Exercise (lactic acid)
How does the body compensate for metabolic acidosis?
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?
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.

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