LQB185 Chapter Notes - Chapter 27: Extracellular Fluid, Fluid Compartments, Metabolic Water
25 May 2018
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Chapter 27- Fluid, Electrolyte and Acid-base Balance
27.1 Fluid Compartments and Fluid Homeostasis
➢ Body fluid- inside and outside cells
➢ 2/3 of body fluid is intracellular fluid
➢ 1/3 is extracellular fluid
- 80% of that is interstitial fluid
- 20% is plasma
➢ Source = ingestions or metabolic water
27.3 Acid-base Balance
➢ Major homeostatic challenge is keeping H+ concentration (pH) of body
fluids at the appropriate level.
➢ Critical to normal cellular function
➢ 3-D shape of all proteins (enables them to perform specific functions) is
very sensitive to pH changes
➢ Several mechanisms help maintain pH of systemic arterial blood
between 7.35-6.45
➢ Metabolic reactions produce high excess of H+, the lack of any
mechanism for disposal of H+ would cause pH to a lethal level
➢ Homeostasis of H+ is essential to survival
➢ Removal of H+ depends on 3 mechanisms:
1. Buffer System: buffers act quickly to temporarily bind H+, removing
the highly reactive, excess H+ from solution. Buffers raise pH of body
fluids but do not remove H+ from the body
2. Exhalation of Carbon Dioxide: by increasing rate and depth of
breathing, more carbon dioxide is exhaled. Thus reducing levels of
carbonic acid in blood, which raises the blood pH (reducing blood H+)
3. Kidney Excretion of H+: slowest mechanism, eliminate acids through
excretion in urine.
➢ ACTIONS OF BUFFER SYSTEMS
- Consist of a weak aid and it’s salt, whih funtions as a weak ase.
- Buffers prevent rapid, drastic changes in the Ph by converting strong
acids and bases into weak acids and bases with a fraction of a second.
- Strong acids lower Ph more than weak acids
- Strong Bases raise Ph more than weak ones
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