1. Fluid–Electrolyte and Acid–Base Balance

2. Fluids and electrolytes
Water makes up 55% to 75% of the total body weight.
Electrolytes are the positive and negative ions present in body fluids.
These ions have specific functions and a range of the amount in each fluid needed for homeostasis.
Question: What other names are appropriate for most electrolytes?
Electrolytes are chemicals that dissolve in water and dissociate into ions; most are inorganic.
Electrolytes some of them are involved in maintenance of normal pH in body fluids.
نحن كائنات ملحيه ومائيه ولكنا لسنا مالحين كالبحر مثلا.

3. Answer
Most electrolytes are minerals, or salts, and many may also be called trace elements.

4. Water compartments
The fluid sites in the body are called Water compartments.
Intracellular fluid (ICF) – water within cells; about two-thirds of total body water.
Extracellular fluid (ECF) – water outside cells. This includes:
Tissue fluid
Plasma
Lymph
Specialized fluids
Question: Name some specialized fluids.

5. Answer
Specialized fluids include cerebrospinal fluid, aqueous humor, synovial fluid, urine, and digestive fluids such as bile.

6. Water compartments (continued)
The chambers of the heart and all blood vessels form one compartment. And water within it is called plasma.
By the processes of filtration in capillaries some plasma is forced out into tissue space (another compartment) and is then called tissue fluid.
When tissue fluid enters the cells by the process of osmosis, it has moved to still another compartment and is called Intracellular fluid (ICF).
The tissue fluid that enters the lymph capillaries is in yet another compartment and is called lymph.

7. Water compartments (continued)
Water is always moving from one compartment to another by processes of
Filtration –
Osmosis –
Osmosis is regulated by the concentration of electrolytes in body fluids (osmolarity).
In osmosis water will diffuse through membranes to an area of greater electrolyte concentration.
Water and electrolytes are constantly moving between compartments, their concentrations remain constant. Maintaining their homeostasis is essential for life : Edema
Filtration in capillaries forcing plasma out.
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass. Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size and filter thickness).
A water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process.

8. Water intake Liquids – 1600 mL (average per 24 hours). Foods – 700 mL.
Metabolic water – 200 mL.
Total water intake per 24 hours is about 2.5 liters.
Variations are possible.
Question: Where does metabolic water come from? Be as specific as you can be.

9. Answer
Metabolic water comes from cell respiration, specifically the cytochrome (electron) transport system (the third stage).

10. Water output Urine – 1500 mL (average per 24 hours). Sweat – 500 mL.
Exhaled water vapor – 300 mL.
Feces – 200 mL.
Total water output per 24 hours is about 2.5 liters:
Variations are possible and must be compensated for by changes in fluid intake.

11. Regulation of water intake and output
Hypothalamus – contains osmoreceptors that detect changes in osmolarity of body fluids. Osmolarity is the concentration of dissolved materials present in a fluid.
Dehydration rises osmolarity.
Dehydration – stimulates the sensation of thirst.
Urinary output –
Hormones involved in correcting dehydration:
ADH –increases water reabsorption by kidney
Aldosterone –increases sodium reabsorption by kidney

12. Several other factors cause water loss
Excessive sweating
Hemorrhage
Diarrhea
Vomiting
Severe burns
Fever

13. Regulation of water intake and output (continued)
Overhydration – too much water.
Urinary output –
ANP – is a hormone involved in correcting overhydration:
atrial natriuretic peptide (ANP), increases sodium excretion and decreases blood pressure and blood volume.

14. Electrolytes
Electrolytes are chemicals that dissolve in water and dissociate into ions; most are inorganic.
Ions can be positive or negative ones
Cations – have a positive charge:
Anions – have a negative charge:
The presence of electrolytes in the water compartments influences osmosis between compartments.
Most organic compounds are nonelectrolytes , that is they do not ionize in solution.
Glucose dissolve in water but does not ionize. يبقي كما هو
البروتينات بعضها يشكل روابط ايونيه

15. Electrolytes in body fluids (see Table 19–2)
ICF – The principal cation is K+.
The principal anion is HPO4–2. (phosphate)
Protein anions are abundant.
Blood plasma –The principal cation is Na+.
The principal anion is Cl–.
Protein anions are significant.
Tissue fluid – similar to plasma, except that protein anions are insignificant.
Question: To which of these fluids is cerebrospinal fluid similar, and why?

16. Answer
Cerebrospinal fluid is similar to tissue fluid, because it is the tissue fluid of the central nervous system.

17. Electrolyte intake and output
Intake – electrolytes are present in foods and beverages.
Output – electrolytes are lost in urine, feces, and sweat.
Question: Which electrolytes are the primary ones lost in perspiration?

18. Answer
Sodium and chloride ions are the main electrolytes lost in perspiration.

19. Electrolyte regulation
Hormones involved:
Aldosterone –
ANP –
Parathyroid hormone: It acts to increase the concentration of calcium (Ca2+) in the blood.
calcitonin –acts to decrease calcium concentration.

20. Acid–base balance Normal pH ranges: ICF – 6.8 to 7.0 Blood –7.35-7.45
Tissue fluid – similar to the pH range of blood.
These ranges are maintained by:
Buffer systems
Respiratory system
Kidneys

21. Buffer systems
A buffer system consists of a weak acid and a weak base.
These chemicals react with strong acids or bases to change them to substances that do not greatly affect pH.
Buffer systems react in less than a second.
Buffer systems have the least capacity to prevent great changes in pH.
Three systems:
Bicarbonate buffer system
Phosphate buffer system
Protein buffer system

22. Bicarbonate buffer system
Bicarbonate buffer system – important in blood and tissue fluid.
Consists of sodium bicarbonate (NaHCO3 ) a weak base and carbonic acid (H2CO3 ) a weak acid
If potential pH change is created by a strong acid, the following reaction takes place:
HCl (strong acid) + NaHCO NaCl + H2CO3 (a weak acid )
NaCl salt, has no effect on pH
H2CO3 ( is a weak acid ) has little effect on pH
If potential pH change is created by a strong base, the following reaction takes place:
NaOH (strong base) + H2CO H2O + NaHCO3 (a weak base )
Consists of sodium bicarbonate (NaHCO3 ) a weak base and carbonic acid (H2CO3 ) a weak acid , in a ratio of 20 to 1.

23. Phosphate buffer system
Phosphate buffer system – important in ICF and in the kidneys.
Consists of Sodium dihydrogen phosphate NaH2PO4 (a weak acid ) and Sodium monohydrogen phosphate Na2HPO4 ( a weak base ).
If potential pH change is created by a strong acid, the following reaction takes place:
HCl (strong acid) + Na2HPO NaCl + NaH2PO4 (weak acid )
If potential pH change is created by a strong base, the following reaction takes place:
NaOH (strong base) + NaH2PO H2O + Na2HPO4 (a weak base )
The cells of kidney tubules can remove excess hydrogen ions by forming NaH2PO4 which is excreted in urine.
The retaind Na ions are returned to the blood in peritubular capillaries along with bicarbonate ions.

24. Protein buffer system Protein buffer system – most important in ICF.
An amino acid may act as an acid or a base.
The carboxyl group may act as acid ( – COOH) because it can donate a H+ ion to a fluid to counteract increasing alkalinity.
The amino group (– NH2) may act as base because it can pick up an excess H+ ion to counteract increasing acidity.

25. Respiratory mechanisms
The respiratory system affects pH because it regulates the amount of CO2 present in body fluids.
The respiratory system may be the cause of a pH imbalance or may help correct a pH imbalance from some other cause.

26. Respiratory Mechanisms (continued)
Respiratory acidosis – the result of anything that decreases the rate or efficiency of respiration.
CO2 cannot be exhaled as fast as it is formed during cellular respiration
Causes –emphysema, asthma, pneumonia ext.
Effect on CO2 in the body:
Effect on H+ ion concentration in the body:
Question: State the reaction that takes place as CO2 accumulates.
Respiratory acidosis : emphysema, asthma, pneumonia

27. Answer As more CO2 accumulates, more H+ ions are formed:
CO2 + H2O  H2CO3  H+ + HCO3–

28. Respiratory mechanisms (continued)
Respiratory alkalosis – the result of breathing more rapidly.
Causes – anxiety, high altitude,..ext.
fewer CO2 in the body fluids.
fewer H+ ions are formed . pH rises
Respiratory alkalosis

29. Respiratory mechanisms (continued) Respiratory compensation for pH metabolic changes:
Changes in pH caused by other than respiratory disorders are called metabolic acidosis or metabolic alkalosis.
In either case the respiratory system can help prevent drastic change in pH.

30. Uncontrolled diabetes mellitus Diarrhea Vomiting
Respiratory compensation for metabolic acidosis: Causes of metabolic acidosis:
Kidney dieses
Uncontrolled diabetes mellitus
Diarrhea
Vomiting
Reduction in pH will stimulate the respiratory in medulla.
Respiration will increase in rate and depth –
More CO2 will be exhaled which will decrease H+ formation.
Uncontrolled diabetes mellitus: patients with ketoacidosis : metabolic acidosis.

31. Respiratory compensation for metabolic alkalosis:
Causes of metabolic alkalosis:
Overuse of antacid medication.
Vomiting of stomach content only
Respiratory rate will decrease –
Less CO2 will be exhaled (more CO2) which will increase H+ formation.
Help in lowering ph back to normal.
Antacids are taken to relieve heartburn or indigestion caused by excess stomach acid.
Causes of metabolic alkalosis:
Overuse of antacid medication.
Vomiting of stomach content only
Vomiting is different from regurgitation, although the two terms are often used interchangeably. Regurgitation is the return of undigested food back up the esophagus to the mouth, without the force and displeasure associated with vomiting

32. Respiratory mechanisms (continued)
The respiratory system responds quickly to pH changes – within 1-3 min
For an ongoing pH imbalance, respiratory compensation is limited –
Only 50-75% effective

33. Renal mechanisms
The kidneys have the greatest capacity to buffer an ongoing pH change because they can remove H+ ions from the body.
Time needed to take effect : several hours to days
In response to acidosis, the kidneys will excrete H+ ions
The kidneys will retain Na+ ions and HCO3- ions.
In response to alkalosis, the kidneys will excrete Na+ ions and HCO3- ions
The kidneys will retain H+ ions
Time needed to take effect : several hours to days but once they do they continue to be effective longer than Respiratory mechanisms .
Uncontrolled diabetes mellitus: patients with ketoacidosis : metabolic acidosis.
Acidic ketones accumulate in the blood : breathing rate increase. Kidney excretes H+ ions

34. Effects of pH changes
Acidosis affects CNS – depresses impulse transmission at synapses in the central nervous system.
Result –person become confused, disoriented then lapses into coma.
Alkalosis – increases synaptic transmission in the peripheral and central nervous system.
Result – irritability of muscle twitches. Progressive alkalosis : severe muscle spasm, and convolutions.

35. Wrap-Up Question
Name the part or aspect of acid–base or fluid–electrolyte
balance described .
1. pH below 7
2. Mineral ions in water
3. Chemical pairs that lessen changes in pH
4. Greatest daily water loss
5. Most abundant cation in tissue fluid
6. Most abundant intracellular cation
7. Normal pH range of blood
8. Have the greatest capacity to buffer a pH change

36. Answers 1. pH below 7 – acidic 2. Mineral ions in water – electrolytes
3. Chemical pairs that lessen changes in pH – buffer systems
4. Greatest daily water loss – urine
5. Most abundant cation in tissue fluid – sodium
6. Most abundant intracellular cation – potassium
7. Normal pH range of blood – 7.35 to 7.45
8. Have the greatest capacity to buffer a pH change – kidneys