Acid-Base Balance

Question 1

What is normal pH?

Answer 1

7.35-7.45

Question 2

What defines acidosis?

Answer 2

pH

Question 3

What defines alkalosis?

Answer 3

pH> 7.45

Question 4

What occurs when [H+] is too high?

Answer 4

H+ diffuses into cells and K+ moves out resulting in hyperkalemia which can depress excitability

Question 5

What happens when [H+] is too low?

Answer 5

H+ will diffuse out of the cell and K+ will move into the cell causing hypokalemia making the cells hyper excitable

Question 6

What is an acid?

Answer 6

a hydrogen ion donor

Question 7

example of a strong acid

Answer 7

HCl

Question 8

example of a weak acid

Answer 8

HAc

Question 9

What is a base?

Answer 9

hydrogen ion accepter; it takes hydrogen ions out of solution

Question 10

What are the 3 systems that defend pH homeostasis?

Answer 10

chemical buffers
the lungs
the kidneys

Question 11

How does a buffer work?

Answer 11

minimizes pH changes in the presence of an acid or alkaline load; it does this very rapidly and is effective only when there is a disturbance

Question 12

How do the lungs help with regulating plasma pH?

Answer 12

they have the ability to control CO2 very rapidly

Question 13

How do the kidneys help with regulating plasma pH?

Answer 13

due to their ability to variably reabsorb HCO3– and secrete H+

Question 14

Where does most of bicarbonate reabsorption occur?

Answer 14

in the proximal nephron segments

Question 15

What do we depend on to reabsorb bicarbonate?

Answer 15

carbonic anhydrase

if this is inhibited in renal cells, then HCO3- reabsorption stops and we become acidotic

Question 16

What happens if a large quantity of H+ is added to the blood?

Answer 16

insufficient HCO3- absorption

excess H+ ions would need to be removed to be excreted in the urine

Question 17

What happens if carbonic anhydrase is inhibited?

Answer 17

H+ secretion slows down and we become acidotic

Question 18

How is the urine never less than 5 pH?

Answer 18

it has titratable acids in the tubular fluid
also tubular cells synthesize ammonia (NH3) which is a strong base and forms ammonium (NH4+) which is excreted in the urine

Question 19

What are the 2 factors related to effectiveness of a buffer system?

Answer 19

-the conc. of the buffers
higher conc.=greater capacity to minimize pH changes
-the Ka of the system
goal is to have the pKa near the desired pH target

Question 20

What is the pKa of an ideal buffer system?

Answer 20

about 7.4

Question 21

list the buffers in ECF

Answer 21

bicarbonate
phosphate
amino acids
hemoglobin

Question 22

what does the ratio of acid/base need to be near for the pH to be normal?

Answer 22

the ratio needs to be near 20 for a pH to be normal (7.4)

Question 23

What is metabolic acidosis?

Answer 23

when the pH is too low because [HCO3-] is too low

Question 24

What can cause metabolic acidosis?

Answer 24

due to addition of fixed acids (lactic acid, ketoacids) or loss of HCO3 (uncontrolled diabetes, starvation, low carb diet, exercise, hypoxia)
- HCO3– may be lost in GI secretions via diarrhea
decreased ability of the kidney to reabsorb bicarbonate or secrete H+ (kidney disease)

Question 25

How do we try to compensate during metabolic acidosis?

Answer 25

buffering by base component of system! - hyperventilation to decrease PCO2 (rapid)! - kidneys will reabsorb all filtered HCO3– and synthesize new HCO3– (secrete H+) (takes hours to days)! - the result is that hyperventilation moves the acid/base ratio closer to 20 and, over days, the kidneys will restore the HCO3– used to buffer H+

Question 26

signs and symptoms of metabolic acidosis

Answer 26

``` hyperventilation! • depression of nervous system activity! - weakness! - fatigue! - confusion! - motor impairments! - headache! - decrease in bone mineral density (in chronic acidosis) ```

Question 27

What is metabolic alkalosis?

Answer 27

pH is too high because HCO3- is too high

Question 28

What are the responses to metabolic alkalosis?

Answer 28

buffering by acid component of system! - hypoventilation to increase PCO2 (rapid)! - kidneys will stop synthesizing new HCO3– (secrete H+) and fail to reabsorb all the filtered HCO3–! • bicarb will be excreted in urine, creating an alkaline urine with pH up to 9.0! - the result is that hypoventilation moves the acid/base ratio closer to 20 and, over days, the kidneys will reduce the HCO3– levels back to normal!

Question 29

What causes metabolic alkalosis?

Answer 29

chronic vomiting hypokalemia (pulls K+ out of cells) volume depletion

Question 30

What are signs and symptoms of metabolic alkalosis?

Answer 30

hypoventilation | excitation of NS- seizures

Question 31

What is respiratory acidosis?

Answer 31

pH is too low because PCO2 is too high

Question 32

What causes respiratory acidosis?

Answer 32

decrease in alveolar ventilation lung disease (obstructive or restrictive) depressed respiratory centers after head trauma chest abnormalities or muscle weakness

Question 33

signs and symptoms of respiratory acidosis?

Answer 33

SOB wheezing headache blurred vision

Question 34

What is respiratory alkalosis?

Answer 34

pH is too high because PCO2 is too low; not as common

Question 35

What is the body's response to respiratory alkalosis?

Answer 35

buffers and respiratory system can not help out the kidneys do most of the work by decreasing HCO3- therefore acid/base ratio is moved closer to 20 and the pH is lowered

Question 36

what causes respiratory alkalosis?

Answer 36

hyperventilation due to panic attacks, fever or altitude

Question 37

signs and symptoms of respiratory alkalosis?

Answer 37

hyperexcitability of CNS- seizures

Question 38

What does a positive value for base excess indicate?

Answer 38

alkalosis

Question 39

What does a negative value for base excess indicate?

Answer 39

acidosis

Question 40

If a pH sample was reported as 7.47 what would this most likely mean?

Answer 40

that the hydrogen ion concentration was less than normal

Question 41

in a condition of respiratory acidosis, the HCO3-/CO2 ratio is what?

Answer 41

It is too low because PCO2 is too high

Question 42

A patient is in a state of metabolic alkalosis. Which condition in the patient's chart is most likely to contribute to this acid-base disturbance?

Answer 42

excessive vomiting