Acid-base balance
From Iusmphysiology
(Difference between revisions)
24.15.60.132 (Talk)
(Created page with '*started here on 03/30/11. ==Acid-base balance== ===Objectives=== *Define the following: acid, base, buffer, pH. Give the normal range of arterial blood pH and the limits comp…')
Newer edit →
(Created page with '*started here on 03/30/11. ==Acid-base balance== ===Objectives=== *Define the following: acid, base, buffer, pH. Give the normal range of arterial blood pH and the limits comp…')
Newer edit →
Revision as of 14:48, 19 April 2011
- started here on 03/30/11.
Contents |
Acid-base balance
Objectives
- Define the following: acid, base, buffer, pH. Give the normal range of arterial blood pH and the limits compatible with life. Explain why constancy of pH is important.
- State the isohydric principle. List the important chemical buffers present in extracellular fluid, intracellular fluid, and bone.
- Write the Henderson-Hasselbalch equation for the bicarbonate/CO2 system. Write Henderson's equation for calculating [HCO3-] from [H+] and PCO2 measurements.
- Explain why the bicarbonate/CO2 system is so important.
- List the four simple acid-base disturbances. Describe for each: 1) the primary defect, 2) changes in arterial blood chemistry (pH, PCO2, and plasma [HCO3-]), 3) some common causes, 4) chemical buffering processes, and 5) respiratory and renal compensations.
- Given plasma electrolyte concentrations, calculate and interpret the anion gap.
- Given values for arterial blood pH, plasma [HCO3-], and PCO2 (or any two of the three), be able to identify the type of acid-base disturbance present.
Normal pH in arterial blood
- A normal pH is 7.4 (7.38-7.42), at which point the concentration of H+ is 40 (38 - 42) nmol / liter.
- Survivable pH is 7.0-7.6 which is considered acidosis and alkalosis, respectively.
- Note that this is a four fold change in H+ concentration.
- Death by change in pH occurs as a result of the changes in intracellular proteins upon change in pH.
Threats to pH of extracellular fluid
- There are two major forces that affect extracellular pH: oxidative phosphorylation and protein metabolism.
- Both of these processes produce sources of acid: oxidative phosphorylation produces CO2 and protein metabolism produces H2SO4 and HCl.
- Oxidative phosphorylation as a source of extracellular acid:
- Recall that oxphos dumps electrons onto oxygen and secretes this waste as CO2.
- Recall that CO2--via carbonic anhydrase--affects the extracellular levels of H+ and HCO3-.
- That is, as CO2 rises, more H2CO3 and H+ are found in the blood; the pH decrease.
- We say CO2 is a volitile acid because it indirectly affects H+ levels.
- 13-20 moles of CO2 are produced each day by oxphos.
- Protein metabolism as a source of extracellular acid:
- Recall that proteins are digested for energy and as a source of amino acids.
- Metabolism requires the removal and storage of the many hydrogens on the proteins and thus can generate H+.
- Met or Cys metabolism generates H2SO4.
- Lys or Arg metabolism generates HCl.
- We say protein metabolism generates fixed acids because it directly affects H+ levels.
- 40-60 moles of fixed acid are produced each day by protein metabolism.