Fluids & Electrolytes Flashcards
Define and describe the measurement of pH.
pH literally means the “potential of hydrogen”. It is a measure of the amount of hydrogen ions present per litre of a solution, expressed in grams.
pH values are expressed on a scale that ranges from 0 to 14. The central point of the scale is pH 7, and it indicates a neutral solution. Values below 7 indicate an acidic solution and values above 7 indicate a basic or alkaline solution.
Describe the electrolyte composition of the body.
As you will recall, there are two major fluid compartments in the body: the intracellular and extracellular fluid. Extracellular fluid can be further divided into mainly the interstitial fluid and blood plasma
Describe the mechanisms for the control of electrolytes in the body.
The first mechanism of pH regulation involves the respiratory system. We have already mentioned how CO2 contributes to total body acidity. In fact, by regulating the total CO2 released through the lungs, we are regulating body pH. An increased rate of gas exchange will result in a greater loss of CO2 and a reduction of acidity in the body. Conversely, reducing ventilation will increase the acidity of the body.
A second mechanism is through the urinary system. The kidneys have the capacity to either retain or excrete hydrogen ions. If the blood pH is too low (too acidic), the kidneys will secrete and excrete hydrogen ions. On the other hand, if the blood pH is too high (too basic), the kidneys can reabsorb more hydrogen ions. Therefore the kidneys play a very important role in preventing any major change in blood pH.
A third method involves the use of buffers. Buffers generally provide an immediate, short-term mechanism for resisting changes in pH, whereas the respiratory and excretory mechanisms are more long-term in nature. A buffer is a substance that resists a rapid change in hydrogen ion concentration. This can be achieved by: i) absorbing some of the hydrogen ions that are added to a solution with the addition of an acid; or ii) donating hydrogen ions to a solution, to replace some of the hydrogen ions lost when a base is added.
