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ANATOMY & PHYSIOLOGY II Lecture #16: Fluid and Balance

I. INTRODUCTION

The is about 60 % by weight. All the body's cells are continuously bathed in fluid, which brings them nutrients and carries away waste materials. The fluid in the tissues, called interstitial fluid, is continually exchanged with fluid from plasma and with the fluid located inside cells. The distribution of the body's fluids is controlled in part by the electrolyte concentration in each compartment. In addition, are vitally important to many key processes in the body.

II.

A. DEFINITION - Fluid balance is the state in which the total amount of water in the body is normal and remains relatively constant. However, not only must the total volume remain relatively constant, but the distribution of the fluid in the must also be correct.

B. DISTRIBUTION OF BODY FLUIDS

The body contains about 40 L of water, which makes up roughly 60% of our total body weight. This is distributed as follows:

1. Intracellular fluid (ICF) - The water located within the cells of the body makes up about 2/3 of the total fluid (about 25 L). Its function is to facilitate the chemical reactions in the cells that maintain life.

2. (ECF) - The water located outside of the cells makes up about 1/3 of the total fluid (about 15 L). It is distributed in the following compartments:

a. (about 3 L) – the fluid portion of the blood. b. Interstitial fluid (about 12 L) – the fluid in the tissue spaces around cells. c. (less than 1 L) – the fluid in lymph vessels.

* Extracellular fluid serves two important functions: (1) it provides a constant environment for the cells, and (2) it transports substances to and from the cells.

2 C. GENERAL PRINCIPLES

1. Balance can be maintained only if intake equals output. Obviously, if more water is entering the body than leaving, fluid volume will increase and an imbalance will occur. Conversely, if more water is being excreted than is entering the body, the fluid volume will decrease and, again, we have an imbalance.

2. When more water enters the body than leaves we have a positive water balance. On the other hand, when more water is excreted than is taken in we have a negative water balance.

3. Mechanisms for controlling fluid output so that it matches fluid intake are very crucial and we will study these in some detail. Mechanisms to control intake also operate but are less elaborate.

4. The amount of fluid in a given individual is directly proportional to his or her total body surface area.

D. ROUTES OF FLUID INTAKE AND OUTPUT

1. Obligatory water loss - even under ideal conditions the body will lose about 700 mL per day through the lungs and skin. An additional 500 mL per day is lost as in order to rid the body of waste products. These are minimum values that occur even if we do not sweat or defecate.

2. Average daily body exchange of water in a temperate climate:

Intake Output Water & other beverages 1500 ml Lungs 550 ml Water in solid 750 ml Skin 150 ml Water of oxidation 250 ml Sweat 200 ml (from cellular ) 2500 ml Feces 100 ml Urine 1500 ml 2500 ml

To Do: Tell if each of these is part of or refers to the intracellular (I) or the extracellular fluid compartment E).

Lymph Plasma Interstitial fluid

Contains most of the body’s water Fluid located between tissue cells

Transports substances in body Provides medium for chemical reactions to occur

Answer the following:

If you urinate more than you drink, you are in: a) positive water balance; b) negative water balance

Obligatory water loss is: a) the amount of water we lose after vigorous exercise as sweat; b) loss that results in a negative water balance; c) the minimum amount of water lost each day.

Other than urine, most water is lost through the: a) skin; b) lungs; c) sweat; d) feces.

3 E. MECHANISMS FOR MAINTAINING NORMAL FLUID DISTRIBUTION

1. Control of Water Movement Between Plasma and Interstitial Fluids

a. To move between the plasma and the interstitial fluid compartment, fluid must pass across the wall of the . This movement is controlled by: 1) Hydrostatic pressure () – tends to force fluid out of the 2) Osmotic pressure due to plasma – tends to draw fluid into the capillary. b. This creates a "tug of war" – If the hydrostatic pressure is greater than the osmotic pressure, fluid will move into the interstitial fluid. If the osmotic pressure is greater, then fluids will move into the plasma. c. Any factor that causes a change in either the hydrostatic or osmotic pressure will affect the movement of fluid between these compartments. Examples: 1) Liver damage can cause fewer plasma proteins to be made, so the osmotic pressure in the capillary will decrease, causing more fluid to enter the interstitial fluid. 2) A drop in blood pressure allows more fluid to flow into the plasma from the interstitial space, which helps to restore the blood pressure.

2. Control of Water Movement Between Interstitial and Intracellular Fluids

a. To move between the interstitial fluid and the intracellular fluid compartments, fluid must cross the membrane. b. Movement is mainly controlled by the osmotic pressure in the two compartments. This will be determined by the electrolyte concentration in each compartment. c. Cells normally pump out of the cell and in, which causes excess sodium to accumulate in the interstitial fluid. d. A higher than normal sodium concentration in the interstitial fluid will draw water out of the cells, and a lower than normal sodium concentration will cause more water to flow into the cells.

To Do: For each of the following statements, decide which direction fluid would tend to move. Use these choices:

B = into the blood I = into the interstitial fluid C = into the cells

Lower than normal sodium levels. Low blood pressure. Higher than normal sodium levels. Lower than normal levels of plasma proteins. High blood pressure. Higher than normal levels of plasma proteins.

4 F. MECHANISMS FOR MAINTAINING TOTAL FLUID BALANCE

1. Two Problems – The body must deal with two separate problems when maintaining fluid balance: a. It must keep the concentration of body fluids in the correct range. b. It must keep the total volume of fluid in the correct range. These are controlled by two different but interrelated systems.

2. Maintaining the Proper Concentration of Body Fluids

a. The total concentration of dissolved material in the blood plasma must be maintained in a fairly narrow range to assure proper functioning. Thus when the body senses that the plasma is becoming either too dilute or too concentrated it makes adjustments to correct the imbalance. b. Nervous control – when the plasma becomes too concentrated, the vagus nerve stimulates feelings of dryness in the mouth and throat, causing us to drink fluids. c. Antidiuretic (ADH) is the main hormone involved in this process. ADH causes the kidneys to reabsorb more water from the filtrate, thus increasing the amount of water in the plasma and diluting the solutes.

plasma concentration stimulates (too little water, too much sodium) negative in hypothalamus water balance

ADH release water intake water output

water intake water output thirst ADH release

positive osmoreceptors water balance in hypothalamus

inhibits plasma concentration (more water, less sodium)

To Do: Mark whether each of these occurs when the plasma is too dilute (D) or too concentrated (C).

Osmoreceptors in hypothalamus are stimulated. Vagus nerve causes feelings of thirst. Osmoreceptors in hypothalamus are inhibited. Feelings of thirst decrease. ADH secretion decreases. Water output decreases (more reabsorption) ADH secretion increases. Water output increases (less reabsorption)

5 3. Maintaining the Proper Total Volume of a. The total volume in each of the fluid compartments must remain fairly constant. b. The plasma volume is especially important because it directly affects blood pressure. c. Too little fluid in the plasma compartment would result in hypovolemic shock and possibly death. d. Too much fluid in the plasma results in high blood pressure and extra stress on the and vessels of the brain. e. is the primary hormone involved in the process of maintaining the correct fluid volume. f. The -angiotensin-aldosterone pathway regulates the release of aldosterone:

Plasma volume Plasma volume

Blood pressure Tubular Na+ reabsorption & H2O reabsorption (with ADH) Renin secretion by juxtaglomerular apparatus Plasma aldosterone

Plasma renin levels Aldosterone release catalyzes by adrenal cortex conversion of Angiotensinogen Angiotensin I Plasma angiotensin II

g. Aldosterone directly stimulates reabsorption of sodium by the tubules. h. If some ADH is also present, which will be the case as long as the plasma concentration is normal or somewhat concentrated, then water will follow sodium by . i. As a result, the fluid reabsorbed will contain both sodium and water and will be isotonic with plasma, so it does not change the overall plasma concentration but it does increase the volume of the blood plasma. j. An isotonic is one that has the same electrolyte concentration as body fluids.

To Do: Indicate whether each of the following would occur when fluid volume is too high (H) or too low (L).

Hypovolemic shock Decreased angiotensin II levels High blood pressure Increased aldosterone secretion Decreased renin secretion Decreased aldosterone secretion Increased renin secretion Increased reabsorption of sodium Increased angiotensin II levels Decreased reabsorption of sodium If ADH is present, what effect will the absorbed fluid have on plasma concentration? a) it will make it more dilute b) it will make it more concentrated c) it will not change it

6 4. Interactions Between ADH and Aldosterone

Usually ADH and aldosterone work together to keep fluid balance correct. Both help water to be reabsorbed and so maintain the proper amount of fluid in the body. But by having two separate systems it allows the body to fine tune the substances reabsorbed in the kidneys according to the body’s needs.

a. Sodium depletion due to excess water intake – When a person drinks a large amount of fluid but does not consume sodium, the body needs to eliminate the excess water while at the same time reabsorbing as much sodium as possible. In this situation aldosterone will be secreted to stimulate sodium reabsorption, but very little ADH will be secreted so the excess water will be excreted in the urine.

b. Sodium excess – In some situations there is too much sodium in the body. This can occur either from too much , or as part of the process when a person takes in little or no water. In this case aldosterone secretion declines while ADH secretion increases. Sodium is not reabsorbed in the kidneys, but water is conserved.

5. Factors Which Affect Fluid Loss Under Abnormal Conditions

a. Hyperventilation for an extended period of time - The patient is rapidly with shallow breaths. Each time air is expelled from the lungs, fluid is lost as water vapor.

b. , , etc. - These cause a loss of fluid, which can lead to an imbalance.

REVIEW OF FLUID BALANCE – Answer the following questions: Fluid balance means that: a) the total volume of fluid is normal; b) the distribution of fluid in the various compartments is normal; c) both a and b To maintain fluid balance, output must input. a) be greater than; b) equal; c) be less than Movement between the plasma and interstitial fluid is controlled by: a) osmotic pressure b) hydrostatic pressure; c) both a and b Movement between interstitial fluid and intracellular fluid is controlled by: a) osmotic pressure b) hydrostatic pressure; c) both a and b The hormone that maintains the correct fluid volume is: a) aldosterone; b) ADH; c) angiotensin The hormone that maintains the correct fluid concentration is: a) aldosterone; b) ADH; c) angiotensin Eating salty potato chips without a drink would stimulate release of: a) aldosterone; b) ADH Dehydration due to evaporation of water vapor from the lungs would stimulate release of: a) aldosterone; b) ADH a liter of water without eating would cause more secretion of: a) aldosterone; b) ADH

7 III. ELECTROLYTE BALANCE

A. DEFINITION – Electrolyte balance is when the total concentration of electrolytes in the body as a whole and in each of the fluid compartments is normal and remains relatively constant. However, electrolyte balance also implies that the concentration of each individual electrolyte is normal and remains relatively constant in each fluid compartment.

B. ELECTROLYTE COMPOSITION OF THE FLUID COMPARTMENTS (mEq/l):

Extracellular Intracellular Interstitial Plasma Cations Sodium (Na+) 10 145 142 Potassium (K+) 160 4 5 Magnesium (Mg+2) 35 2 3 (Ca+2) -- 3 5

Total cations: 205 154 155

Anions (Cl-) 2 115 103 - Bicarbonate (HCO3 ) 8 30 27 -2 (HPO3 ) 140 2 2 -2 Sulfate (SO4 ) -- 1 1 - 55 1 16 Organic acids- -- 5 6

Total anions: 205 154 155

General Principles of Electrolyte Distribution: 1. In each fluid compartment, the total concentration of cations (positively charged ions) equals the total concentration of anions (negatively charged ions). 2. The total concentration of ions in the interstitial fluid and blood plasma is about the same. 3. There is a considerable difference in the total concentration of electrolytes between the interstitial and intracellular compartments. This causes the difference in osmotic pressure that regulates the water flow between these two compartments. 4. The predominate cation within the cell is potassium while the predominate cation in the extracellular fluids is sodium.

-2 5. The predominate anion within the cell is HPO4 (monohydrogen phosphate ion) while the predominate anion in the extracellular fluids is chloride.

8

C. IMPORTANCE OF ELECTROLYTE BALANCE 1. Na+ and K+ are the predominate cations in the interstitial and intracellular fluids, respectively. Changes in either of their concentrations will cause an exchange of fluid between these compartments. 2. A fluid imbalance can result when the levels of either Na+ or K+ change. For example, if person takes in a large amount of salt (NaCl), a high Na+ concentration in the plasma and in the interstitial fluid will result. This will increase the osmotic pressure in these compartments and cause a flow of water into the interstitial fluid from the cells. The result will be . 3. Thus, fluid balance depends on electrolyte balance. 4. However, the opposite is also true. If the amount of water in a compartment increases, the concentration of the electrolyte will decrease, resulting in an .

D. CLINICAL IMPORTANCE OF SOME ANIONS AND CATIONS 1. Sodium (Na+) - the primary cation of extracellular fluid. a. Functions: Maintains osmotic pressure of extracellular fluid. Controls water retention in interstitial tissue spaces. Helps maintain blood pressure. Regulates irritability of nerve and muscle tissue and of the heart. b. Notes - The body's sodium concentration is regulated by aldosterone, which promotes the reabsorption of sodium in the kidney tubules. ADH also has an effect on (an is affected by) sodium levels, since it helps regulate water reabsorption and the concentration of body fluids.

2. Chloride (Cl-) - the primary anion of extracellular fluid. a. Functions: Formation and secretion of gastric acid (HCl)

Transportation of O2 and CO2 in the blood (chloride shift). b. Notes – Intake of chloride is closely related to sodium intake in the form of NaCl (table salt)

3. Potassium (K+) - the principle cation of intracellular fluid. a. Functions: Maintains osmotic pressure of cells. Maintains electrical potential of cells, including nerve and muscle. b. Notes – The kidneys do not conserve potassium as well as sodium, thus depletion readily occurs in low potassium diets or if too much is excreted in response to aldosterone. Too much potassium can cause heart arrhythmias or even cardiac arrest. 9 -2 4. Phosphate (HPO4 ) - the primary anion of intracellular fluid. a. Functions: Important in acid-base balance because this ion makes up one of the buffer systems. Important in production of ATP, the body's principle energy compound. b. Notes – Diets with sufficient calcium usually have enough phosphate, because they occur together as calcium phosphate.

5. Calcium (Ca+2) - found almost exclusively in the extracellular fluid (a little is stored in muscle). a. Functions: Structural component of bones and teeth. Needed for muscle contraction and nerve impulse conduction. Involved in nearly all steps of blood clotting. b. Notes – Calcium levels are regulated primarily by parathyroid hormone, and to a lesser extent by calcitonin, which control release and storage of calcium from bone. Calcium is a depressing ion, so if the concentration is low, excitability of nerve and skeletal muscle tissue is increased, and if the concentration is high, excitability is decreased.

6. Magnesium (Mg+2) - primarily an intracellular ion a. Functions: Essential for proper functioning of the neuromuscular system. b. Notes – Deficiency is unusual because it is present in chlorophyll. Like calcium, magnesium is a depressing ion.

To Do: Complete the following:

+ + - -2 +2 +2 Write the symbols for Na , K , Cl , HPO4 , Ca , and Mg either inside or outside the cell to show where most is found.

Which two fluid compartments are most similar in terns of the amounts of electrolytes found there? a) extracellular and intracellular b) interstitial and intracellular c) plasma and interstitial Edema could be caused by: a) lots of salt; b) too much potassium; c) too little sodium True or False: A change in the amount of fluid in a compartment could cause an electrolyte imbalance.

+ + - -2 +2 +2 Match the electrolytes with the statements below. Choices: Na , K , Cl , HPO4 , Ca , and Mg . Forms bones & teeth, needed for blood clotting Helps maintain blood pressure

Maintains electrical potential of cells Forms gastric acid, helps transport O2 and CO2 Depressing ion found in chlorophyll Part of ATP, forms a buffer system for pH

10 IV. FLUID AND ELECTROLYTE IMBALANCES

A. INTRODUCTION

The fluid and electrolyte balance of the body can be thrown off in a number of ways. General examples are: 1. Loss of water without loss of electrolytes (usually by evaporation from lungs and skin). 2. Loss of isotonic fluid (both water and electrolytes) through sweating, bleeding, vomiting or diarrhea, either with no replacement or with replacement of the water only. 3. Intake of excessive amounts of water or salt. 4. Abnormal retention of electrolytes (usually sodium) by the body.

In the following descriptions, ECF = extracellular fluid and ICF = intracellular fluid

B. SIMPLE WATER DEPLETION

1. Simple water depletion occurs when water is lost from the body without an accompanying loss of electrolytes. An example is loss of water vapor from the lungs without replacement by . (This often occurs when water is unavailable, or in bedridden patients or infants who cannot obtain water for themselves).

2. Process: As water is lost, the concentration of electrolytes in the ECF (plasma and interstitial fluid) increases. Water is then osmotically drawn from the cells until the osmotic pressure in both compartments is equal. Because the volume of the ICF is twice that of the ECF, 2/3 of the water loss will be from the ICF and 1/3 will be from the ECF (i.e. cells suffer more than plasma and interstitial fluid).

3. Result: The volume of fluid both inside and outside of the cells is less than normal and the electrolyte concentration of both compartments is greater than normal. This condition is called dehydration.

C. SALT DEPLETION

1. Salt depletion occurs when isotonic fluid is lost from the body (through sweating, diarrhea, bleeding, etc.) and the lost fluid is replaced by alone.

2. Process: Ingestion of water lowers the electrolyte concentration of the ECF. This causes water to osmotically flow into the cells until the concentration of both compartments is equal.

3. Result: The volume of the ECF is decreased, while the volume of the ICF is now greater than normal. Meanwhile, the electrolyte concentrations of both compartments will be decreased. The cells become overhydrated, a condition sometimes referred to as hypotonic hydration or “.”

11 D. SALT POISONING

1. Salt poisoning occurs when excess salt is ingested without drinking water along with it.

2. Process: Ingestion of salt increases the electrolyte concentration in the ECF. This causes water to osmotically flow out of the cells into the ECF until the concentration in both compartments is equal.

3. Result: The volume of the ECF is greater than normal and that of the ICF is less than normal, while the electrolyte concentration of both compartments is greater than normal. Cellular dehydration results.

E. ABNORMAL SODIUM RETENTION

1. More sodium than normal will be retained in the body. This can be caused by hyperaldosteronism and edema related to congestive .

2. Process: As more sodium is retained by the kidneys, water will be retained as well, causing expansion of the ECF with fluid containing normal concentrations of sodium (isotonic expansion).

3. Result: the volume of the ECF increases, but that of the ICF remains normal, since there is no difference in the osmotic pressure between the two compartments. The electrolyte concentration will be unchanged. The result is edema.

To Do: Match the statements with the imbalance they apply to. (Letters match the sections above) b. Simple water depletion d. Salt poisoning c. Salt depletion e. Abnormal sodium retention

Taking a salt tablet without drinking sufficient water. Dehydration resulting from loss of water vapor through the lungs. The kidneys reabsorb too much salt and water due to high levels of aldosterone. A person with diarrhea drinks plenty of water, but doesn’t eat anything. Too little fluid is in the cells and too much is in the plasma and interstitial fluid; the fluid throughout the body has too much salt. The cells remain normal and the fluid concentration is fine, but there is too much fluid in the plasma and interstitial compartment. Fluid throughout the body is too dilute; the cells have too much water while the plasma and interstitial fluid have too little. Both the cells and the plasma and interstitial fluid have too little fluid; all the body’s fluids are too concentrated. 12 Learning Objectives for Lecture #16: Fluid and Electrolyte Balance

After studying this material you should be able to:

1. Explain what is meant by fluid balance and describe the normal distribution of fluid in the different fluid compartments and the functions of the fluid in each compartment.

2. Describe the general principles of fluid balance including the terms positive water balance and negative water balance.

3. Explain what is meant by obligatory water loss, know the sources of water intake and output, and know what source represents the largest intake or output.

4. Describe the factors that control movement of fluid between the plasma and interstitial fluid and between the interstitial and intercellular fluid.

5. Explain how the body maintains the proper concentration of body fluids, including the role of ADH.

6. Explain how the body maintains the proper total volume of body fluid, including the role of aldosterone.

7. Describe the relative amounts of aldosterone and ADH that would be secreted when there is sodium depletion due to excess water intake and when there is sodium excess.

8. Explain what is meant by electrolyte balance and know the general principles of electrolyte distribution.

9. Describe the importance of electrolyte balance and how it is related to fluid balance.

10. For each of the following ions, know the functions, and notes given on them, and where they are + + - -2 +2 predominantly found in the extracellular or intracellular fluid compartment: Na , K , Cl , HPO4 , Ca , and Mg+2.

11. Identify the possible causes, the process that occurs and the end result for each of the following: simple water depletion, salt depletion, salt poisoning, and abnormal sodium retention.

The following CD-ROM, while not required, may help you to visualize the material covered in this lecture. This is available on reserve in the LRC. It is also part of the Interactive Physiology CD that was packaged with new editions of the textbook, and is available online at www.interactivephysiology.com. Use the same user name (login) and password as for the MyA&P website that goes along with the textbook (the course ID is quale12450):

Interactive Physiology, “Fluid and Electrolytes” 13 Lecture #16: Fluid and Electrolyte Balance – Answer Key

Page 2 - Tell if each of these is part of or refers to the intracellular (I) or the extracellular fluid compartment E).

E Lymph I Cytoplasm E Plasma E Interstitial fluid

I Contains most of the body’s water E Fluid located between tissue cells

E Transports substances in body I Provides medium for chemical reactions to occur

Answer the following:

B If you urinate more than you drink, you are in: a) positive water balance; b) negative water balance

C Obligatory water loss is: a) the amount of water we lose after vigorous exercise as sweat; b) loss that results in a negative water balance; c) the minimum amount of water lost each day.

B Other than urine, most water is lost through the: a) skin; b) lungs; c) sweat; d) feces.

Page 3 - For each of the following statements, decide which direction fluid would tend to move. Use these choices:

B = into the blood I = into the interstitial fluid C = into the cells

C Lower than normal sodium levels. B Low blood pressure. I Higher than normal sodium levels. I Lower than normal levels of plasma proteins. I High blood pressure. B Higher than normal levels of plasma proteins.

Page 4 - Mark whether each of these occurs when the plasma is too dilute (D) or too concentrated (C).

C Osmoreceptors in hypothalamus are stimulated. C Vagus nerve causes feelings of thirst. D Osmoreceptors in hypothalamus are inhibited. D Feelings of thirst decrease. D ADH secretion decreases. C Water output decreases (more reabsorption) C ADH secretion increases. D Water output increases (less reabsorption)

Page 5 - Indicate whether each of the following would occur when fluid volume is too high (H) or too low (L).

L Hypovolemic shock H Decreased angiotensin II levels H High blood pressure L Increased aldosterone secretion H Decreased renin secretion H Decreased aldosterone secretion L Increased renin secretion L Increased reabsorption of sodium L Increased angiotensin II levels H Decreased reabsorption of sodium C If ADH is present, what effect will the absorbed fluid have on plasma concentration? a) it will make it more dilute b) it will make it more concentrated c) it will not change it

14 Page 6 - REVIEW OF FLUID BALANCE – Answer the following questions: C Fluid balance means that: a) the total volume of fluid is normal; b) the distribution of fluid in the various compartments is normal; c) both a and b B To maintain fluid balance, output must input. a) be greater than; b) equal; c) be less than C Movement between the plasma and interstitial fluid is controlled by: a) osmotic pressure b) hydrostatic pressure; c) both a and b A Movement between interstitial fluid and intracellular fluid is controlled by: a) osmotic pressure b) hydrostatic pressure; c) both a and b A The hormone that maintains the correct fluid volume is: a) aldosterone; b) ADH; c) angiotensin B The hormone that maintains the correct fluid concentration is: a) aldosterone; b) ADH; c) angiotensin B Eating salty potato chips without a drink would stimulate release of: a) aldosterone; b) ADH B Dehydration due to evaporation of water vapor from the lungs would stimulate release of: a) aldosterone; b) ADH A Drinking a liter of water without eating food would cause more secretion of: a) aldosterone; b) ADH

Page 9 - Complete the following:

+ + - -2 +2 +2 Write the symbols for Na , K , Cl , HPO4 , Ca , and Mg either inside or outside the cell to show where most is found. + +2 + -2 Na Ca K HPO4 Cl - Mg+2 C Which two fluid compartments are most similar in terns of the amounts of electrolytes found there? a) extracellular and intracellular b) interstitial and intracellular c) plasma and interstitial A Edema could be caused by: a) lots of salt; b) too much potassium; c) too little sodium T True or False: A change in the amount of fluid in a compartment could cause an electrolyte imbalance.

+ + - -2 +2 +2 Match the electrolytes with the statements below. Choices: Na , K , Cl , HPO4 , Ca , and Mg . Ca+2 Forms bones & teeth, needed for blood clotting Na+ Helps maintain blood pressure

+ - K Maintains electrical potential of cells Cl Forms gastric acid, helps transport O2 and CO2 +2 -2 Mg Depressing ion found in chlorophyll HPO4 Part of ATP, forms a buffer system for pH

15 Page 11 - Match the statements with the imbalance they apply to. (Letters match the sections above) b. Simple water depletion d. Salt poisoning c. Salt depletion e. Abnormal sodium retention

D Taking a salt tablet without drinking sufficient water. B Dehydration resulting from loss of water vapor through the lungs. E The kidneys reabsorb too much salt and water due to high levels of aldosterone. C A person with diarrhea drinks plenty of water, but doesn’t eat anything. D Too little fluid is in the cells and too much is in the plasma and interstitial fluid; the fluid throughout the body has too much salt. E The cells remain normal and the fluid concentration is fine, but there is too much fluid in the plasma and interstitial compartment. C Fluid throughout the body is too dilute; the cells have too much water while the plasma and interstitial fluid have too little. B Both the cells and the plasma and interstitial fluid have too little fluid; all the body’s fluids are too concentrated.