Acid Base Balance

Question 1

pH scale

Answer 1

negative log scale in that a decrease in one unit of pH increases [H+] by a factor of 10

Question 2

pH of urine

Answer 2

have a wider range compared to other body fluids, usually ~8

Question 3

pH of the stomach

Answer 3

1.5-3

Question 4

pH of saliva

Answer 4

about 6.5

Question 5

physiological alkalosis

Answer 5

arterial pH > 7.45

Question 6

physiological acidosis

Answer 6

arterial pH lower than 7.35

Question 7

buffer system

Answer 7

a mixture of a weak acid and conjugate base which resists changes in pH with reversible equilibrium rxns

Question 8

protein buffer system

Answer 8

proteins and amino acids act as buffers inside cells and blood plasma e.g. hemoglobin (constructed partially of globin protein), carboxyl and amino groups can absorb/give off H+ to dampen pH changes

Question 9

carbonic acid-bicarbonate buffer system

Answer 9

CO2 can combine w/ H2O to produce carbonic acid, which decomposes to yield bicarb. and H+; in turn, increased H+ reduces pH and system shifts right to maintain balance

• when H+ combines w/ bicarb., H2CO3 increases
• system can shift to left to minimize change

Question 10

in what 3 ways is CO2 transported?

Answer 10

directly dissolved in blood plasma, converted slowly into carbonic acid (which will dissociate) or quickly w/ carbonic anhydrase, or as carbamino hemoglobin

Question 11

respiratory acidosis

Answer 11

a drop in blood pH due to poor ventilation and too much CO2

Question 12

respiratory causes of acidosis

Answer 12

damage to lungs/airways/breathing, damage or incapacitation of respiratory centers in medulla, holding in breath or running

Question 13

metabolic acidosis

Answer 13

decreased pH in blood and body tissues as a result of an upset in metabolism

Question 14

causes of metabolic acidosis

Answer 14

anaerobic metabolism prod. lactic acid, kidney dysfunction, incomplete breakdown of fatty acids, consuming a lot of ethanol (converted to acetic acid), normal metabolism, diarrhea

Question 15

respiratory alkalosis

Answer 15

rise in blood pH due to hyperventilation (excessive breathing) and a resulting decrease in CO2

Question 16

respiratory causes of alkalosis

Answer 16

hyperventilation

Question 17

metabolic causes of alkalosis

Answer 17

vomiting, ingestion of bicarbonate, constipation

Question 18

chemoreceptors that regulate respiration

Answer 18

peripheral chemoreceptors at the aortic arch and central chemoreceptors, both travelling to medulla; increases in CO2 and H+ drive ventilation

Question 19

respiratory compensation

Answer 19

• too much acid/lots of CO2: breathe more

- too little acidity/low CO2: breathe less

Question 20

renal compensation

Answer 20

• too much acid: pee out acids

- too much base: pee out base

Question 21

why is renal compensation for acidosis better than respiratory compensation?

Answer 21

b/c HCO3- is preserved by the kidneys (does not cost a bicarbonate by having to combine w/ H+ to dissociate into H2O and CO2 that is blown off)
- kidneys are also the only way of dealing with nonvolatile acids

Question 22

carbonate ion reabsorption and H+ secretion

Answer 22

• high H+ = high CO2 which moves passively into tubular cell
• CO2 + H+ make H2CO3 and then dissociates into bicarb. and H+
• H+ enters filtrate via Na+/H+ antiporter, bicarb. passively reabsorbed into blood
• rapid conversion of carbonic acid w/ carbonic anhydrase allows ion regulation
• CO2 could move in any direction but only the cell can create the bicarb.ions and shunt them back to the blood
• H+ is excreted and the HCO3- is reabsorbed which is not like the respiratory compensation for excess H+

Question 23

how can you determine acid/base status?

Answer 23

1. know pH of blood
2. check value of CO2
   - if CO2 levels agree w/ pH it is respiratory
   - if CO2 levels do not agree w/ pH it is metabolic
3. check bicarb. (direct relationship w/ pH)