Kaplan Prep - Fluid and Electrolyte Balance - Problem Set 3

Question 1

Why is the acid-base balance in the body important?

Answer 1

Operation of all proteins is dependent on the pH of the medium that they function in.

Question 2

What is normal pH of intracellular fluid?

Answer 2

7.0

Question 3

What is the normal pH of venous blood and interstitial fluid?

Answer 3

7.35

Question 4

What is the normal pH of arterial blood?

Answer 4

7.4

Question 5

Define alkalosis

Answer 5

When arterial blood pH exceeds 7.45

Question 6

Define acidosis

Answer 6

When arterial blood pH drops below 7.35

Question 7

Why do venous blood and interstitial fluid have a lower pH?

Answer 7

Because of acidic materials produced by cellular metabolism.

Question 8

What 3 ways is blood acidity (pH) controlled?

Answer 8

1. 3 fast acting chemical buffer systems
2. Brain stem respiratory center
3. Renal system

Question 9

What is the pH of any system dependent on?

Answer 9

The concentration of free H+ present (likely due to the ionization of strong acids)

Question 10

What effect does more H+ have on the pH of a system?

Answer 10

More H+ makes the system more acidic and lowers the pH

Question 11

What do bases produce?

Answer 11

OH-

Question 12

What effect does more OH- have on the pH of a system?

Answer 12

The OH- “uses up” (combines with) the H+ and lowers the concentration of H+ which increases the pH.

Question 13

Why do weak acids not significantly contribute to the pH of a solution?

Answer 13

The H+ is tightly bound and cannot dissociate to become free H+

Question 14

What are the 3 major chemical buffer systems of the body?

Answer 14

1. bicarbonate system
2. phosphate system
3. protein system

Question 15

Which system is the main buffer for the interstitial and plasma fluids?

Answer 15

bicarbonate system

Question 16

Which system acts as a buffer for the urine and intracellular fluid?

Answer 16

phosphate system

Question 17

Which system is the main buffer for the intracellular fluid?

Answer 17

protein system

Question 18

What are chemical acid-base buffers composed of?

Answer 18

1. a weak acid and its anion

2. a weak base and its cation

Question 19

Give an example of a weak acid and its anion

Answer 19

H2CO3 (carbonic acid) and HCO3- (bicarbonate ion)

Question 20

Give an example of a weak base and its cation

Answer 20

NH3 and NH4+

Question 21

How do the chemical acid-base buffer work?

Answer 21

The pairs act to minimize pH changes. One substance of the pair reacts with H+ to prevent a lowering of the pH. The other substance reacts with OH- to prevent the pH from rising.

Question 22

What is the form of CO2 that is transported in the blood plamsa?

Answer 22

HCO3- (bicarbonate)

Question 23

How does the respiratory center respond to a drop in blood pH?

Answer 23

It causes more CO2 to be removed. The H+ gets used up and the pH rises.

Question 24

How does the respiratory center respond to a rise in blood pH?

Answer 24

It causes a depression in the respiratory center which causes an accumulation of CO2. H+ is formed which causes a decrease in pH.

Question 25

What is the only organ that has the ability to remove (rather than just bind) acids and bases from the body?

Answer 25

Kidneys

Question 26

What is the major renal acid-base regulating process?

Answer 26

Excreting or reabsorbing bicarbonate ion

Question 27

What does renal excretion of bicarbonate result in?

Answer 27

Retention of H+

Question 28

What does renal absorption of bicarbonate result in?

Answer 28

Excretion of H+

Question 29

If the concentration of bicarbonate in the filtrate is diminished (used up to buffer the blood) in response to developing blood acidosis what must happen?

Answer 29

The H+ secreted into the filtrate must be buffered and excreted to avoid radical decrease in urine pH

Question 30

What are the 2 mechanisms to avoid a radical decrease in urine pH when bicarbonate is used up to buffer the blood?

Answer 30

1. renal phosphate buffer | 2. ammonia buffer system

Question 31

How does the renal phosphate buffer system work when bicarbonate is used up?

Answer 31

It employs monohydrogen phosphate (HPO4 -2) to bind the H+ as H2PO4- which is excreted in the urine

Question 32

How does the ammonia buffer system work when bicarbonate is used up?

Answer 32

It employs ammonia (NH3) to bind the H+ as NH4+ which is excreted in the urine

Question 33

What happens during alkalosis in the collecting duct?

Answer 33

Collecting duct intercalated cells secrete bicarbonate while simultaneously recovering H+ to lower pH of blood. Bicarbonate combines with H+ to form carbonic acid which is then secreted to the blood where it dissociates to form H+ and bicarbonate which lowers blood pH

Question 34

What are the 2 classifications of acidosis and alkalosis?

Answer 34

``` Respiratory disorder (higher or lower CO2 pressure in blood) Metabolic disorder (some other cause) ```

Question 35

What happens to the body in acidosis?

Answer 35

Central nervous system is markedly depressed causing coma and imminent death

Question 36

What happens to the body in alkalosis?

Answer 36

Nervous system is markedly excited causing extreme nervousness, muscle contraction, convulsion and death ususally due to cessation of breathing

Question 37

Respiratory acidosis is characterized by what and due to what?

Answer 37

Characterized by lower pH due to higher CO2 pressure

Question 38

What specifically causes the lower pH and the higher CO2 pressure in respiratory acidosis?

Answer 38

Shallow breathing or limited gas exchange usually due to cystic fibrosis, emphysema or pneumonia

Question 39

Respiratory alkalosis is characterized by what and due to what?

Answer 39

Characterized by higher pH and due to lower CO2 pressure

Question 40

What specifically causes the higher pH and the lower CO2 pressure in respiratory alkalosis?

Answer 40

Hyperventilation such as in the case of a panic attack

Question 41

Respiratory acidosis and alkalosis can cause the renal system to do what?

Answer 41

Renal system can attempt to correct the disorder (renal compensation)

Question 42

Metabolic acidosis is characterized by what and due to what?

Answer 42

Characterized by lower pH (with normal CO2 levels) due to lower bicarbonate concentration

Question 43

What specifically causes the lower pH and the lower bicarbonate concentration in metabolic acidosis?

Answer 43

Build up of acidic metabolic products such as acetic acid (alcohol overdose), lactic acid (exercise or shock), diabetic ketosis or loss of bicarbonate caused by extreme diarrhea

Question 44

Metabolic alkalosis is characterized by what and due to what?

Answer 44

Characterized by higher pH (with normal levels of CO2) due to higher bicarbonate concentration

Question 45

What specifically causes the higher pH and the higher bicarbonate concentration in metabolic alkalosis?

Answer 45

Vomiting (loss of acidic stomach contents), intake of excess antacids and constipation which caused abnormal reabsorption of bicarbonate

Question 46

Metabolic acidosis and alkalosis can cause the respiratory system to do what?

Answer 46

Respiratory system can attempt to correct acidosis or alkalosis (respiratory compensation)

Question 47

What is the normal blood serum levels for pH?

Answer 47

7.35 - 7.45

Question 48

What is the normal blood serum levels for pressure of CO2?

Answer 48

35 - 45 mm

Question 49

What is the normal blood serum levels for bicarbonate?

Answer 49

22 - 26 mEq/L