Fluid, Electrolyte and Acid-Base Dynamics

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Fluid, Electrolyte and Acid-Base Dynamics
Human Anatomy and Physiology II Oklahoma City Community College This is the presentation on Fluid, Electrolyte and Acid-Base Dynamics for Human Anatomy and Physiology II at Oklahoma City Community College. Dennis Anderson

Concentration of Solutions
Percent Salt 0.9% NaCl Milliosmoles 300 milliosmoles/Liter Milliequivalents 325 milliequivalents/Liter The concentration of solutions can be expressed in several different units. One unit is a percent solution. Body fluids have the equivalent to 0.9% NaCl. Another method of expressing concentration is the number of milliosmoles per liter. This is a unit that expresses the concentration of all the solutes in a solution. Most body fluids have a concentration near 300 milliosmoles/Liter. Milliequivalents represent charged particles. Since our electrolytes have are charged, we usually express their concentration as milliequivalents. Each electrolyte in a solution contributes to the total electrolyte concentration. For example, sodium contributes about 144 milliequivalents of the 325 milliequivalents in the blood.

Osmosis You recall that osmosis is the movement of water across a membrane to the side of the membrane with more solutes. Which way will water move in this example? The concentration of solutes is greater inside the cell in this example. *Water will therefore move into the cell.

Osmosis In this example there are more solutes outside the cell. Which way will water move?

Hypertonic Solution 0.9% NaCl 3% NaCl
In this example a cell with the equivalent of 0.9% NaCl is in a 3% NaCl solution. Which way will water move? *Water will move to the outside of the cell. Since the solution outside the cell has more solutes we say it is a hypertonic solution. 3% NaCl

Cells Crenate in a Hypertonic Solution
Cell in a hypertonic solution lose water. *Crenate is the term to describe the shrinking of the cell.

Hypotonic Solution 0.9% NaCl 0.5% NaCl
Which way will water move in this example? *Water will move into the cell because there are more solutes in the cell. *The solution outside of the cell is hypotonic. 0.5% NaCl

Cells in a Hypotonic Solution Swell and May Lyse
Cells in a hypotonic solution may swell*. If the cell swells too much in will lyse.

Isotonic Solution 0.9% NaCl 0.9% NaCl
An isotonic solution will not cause an excess movement of water in or out of a cell. Most IV solutions are isotonic. 0.9% NaCl

Which Way Will Fluid Move?
300 mosm 310 mosm In this example the concentration is a cell is 300 milliosmoles. The concentration in the blood is at 310 milliosmoles. Which way will fluid move in this example? *Fluid will move into the blood because the solute concentration is higher in the blood.

Application Problem 1 Michael has recently started working outdoors in the hot weather to earn money for his tuition. After a few days he experienced headaches, low blood pressure and a rapid heart rate. His blood sodium was down to 125 meq/L. The normal is 144 meq/L. How do you explain this? Why has Michael’s sodium concentration decreased in his blood in this problem? Also why is he having headaches and a rapid heart rate?

Answer to Problem 1 Michael lost sodium by perspiration. The low sodium in his blood allowed fluid to move into cells by osmosis. Lack of fluid lowered his blood pressure to give him a headache. The increased heart rate was his bodies way of trying to increase blood pressure.

Application Problem 2 Frank has hypertension. His doctor has advised Frank eat a low salt diet. Frank consumed a lot of salt the day before his last checkup. His blood pressure was up. Why? Why was Frank’s blood pressure up in problem 2?

Answer to Problem 2 The extra salt Frank ate made his blood hypertonic. Hypertonic blood will attract fluids from body cells by osmosis. The salt he ate made his blood hypertonic. Hypertonic blood will attract fluids by osmosis.

Electrolyte vrs. Nonelectrolyte
NaCl Na+ + Cl- NaCl is an electrolyte. *It will separate into two particles when placed in water. Glucose is a nonelectrolyte. *It only forms one particle in water. The nonelectrolye glucose does not have as many particles to attract water as the electrolyte NaCl. Glucose Glucose

Carbon Dioxide and Acid
CO2 + H2O H2CO3 H+ + HCO3- Carbonic Acid Carbon dioxide will form carbonic acid as illustrated on this slide. *Carbonic acid will release the hydrogen ion. It is hydrogen ions that determine the pH.

More Carbon Dioxide = More Acid = Lower pH
Breathing slower will retain CO2 , pH will decrease (more acid) Breathing faster will eliminate more CO2 pH will increase (less acid) More carbon dioxide means more acid and a lower pH *By breathing slower the body will retain carbon dioxide and the pH will decrease or become more acidic. *Breathing faster will eliminate more carbon dioxide and the pH will increase or become less acidic.

Blood pH Drops to 7.3 How does the body compensate?
Breath faster to get rid of carbon dioxide eliminates acid If the blood pH drops to 7.3 how does the body compensate? *One thing it will do is breath faster to get rid of carbon dioxide. Eliminating carbon dioxide will eliminate acid and raise the pH.

Blood pH Increases to 7.45 How does the body compensate?
Breath slower to retain more carbon dioxide retains more acid If the pH increases to 7.45 how does the body compensate? *It will breath slower to retain more carbon dioxide. This will increase the acid level in the blood to lower the pH.

John is Taking Narcotics for Pain The narcotics have depressed his breathing rate. What will happen to his blood pH? pH will decrease because he will retain excess carbon dioxide which will increase the amount of acid in the blood John is taking narcotics for pain. The narcotics have depressed his breathing rate. What will happen to his blood pH? *The pH will decrease because he will retain excess carbon dioxide with will increase the amount of acid in the blood.

Buffers Regulate pH Chemicals that resist changes in pH
Prevent large pH changes when an acid or base is added Buffers are chemicals that regulate pH. They prevent large pH changes when an acid or base is added. They do not completely prevent pH changes. Buffers prevent large fluctuations in pH.

Strong Acid Acid that releases many hydrogen ions HCl
A strong acid is an acid that releases many hydrogen ions. HCl is a strong acid.

Weak Acid Acid that releases only a few hydrogen ions Carbonic Acid
Weak acids only release a few hydrogen ions. Carbonic acid is a weak acid.

Buffers Change Strong Acids to Weak Acids
H2CO3 + NaCl Weak Acid Salt HCl + NaOH Strong Acid Base Buffers change strong acids to weak acids. *The strong acid, HCl combines with NaOH, a base in one of the bodies buffer systems. *The reaction produces carbonic acid, a weak acid and salt. The buffer has changed the strong acid, HCl into the weak acid, H2CO3.

Acidosis pH below 7.35 Depresses the nervous system coma
Acidosis occurs when the pH in the blood falls below Acidosis depresses the nervous system. If acidosis is not reversed the person will go into a coma and die.

Alkalosis pH above 7.45 Overexcites the nervous system convulsions
Alkalosis is when the pH is above Alkalosis overexcites the nervous system and can cause convulsion. If alkalosis is not reversed a person can die.