Acid base balance

Question 1

how is pH measured?

Answer 1

-log10[H+] or log 1/[H+]

Question 2

neutral pH is?

Answer 2

7

Question 3

below 7 pH?

Answer 3

acid

Question 4

above 7 pH?

Answer 4

alkaline

Question 5

what do acids do with protons?

Answer 5

donates protons

Question 6

what do alkalis do with protons?

Answer 6

accepts protons

Question 7

stronger acid - H+?

Answer 7

stronger the acid the greater the % of molecules separate to free H+ and anions

Question 8

what pH is needed in a cell for normal cell function?

Answer 8

7

Question 9

slight deviations in pH cause what to change?

Answer 9

protein structure
enzyme activity
nerve excitability

Question 10

what does blood pH depend on?

Answer 10

depends only on the ratio of [HCO3-] to [H2CO3]

Question 11

What is H2CO3?

Answer 11

carbonic acid
a weak acid, a portion dissociates into H+ and HCO3-
Can form from either CO2 + H2O or from H+ + HCO3-

Question 12

what is HCO3-?

Answer 12

bicarbonate ion
H2CO3 part - dissociates into HCO3- and H+
CO2 combines with OH- (forming HCO3-, by carbonic anhydrase)
carbonate (CO32- combines with H+)

Question 13

alterations in body pH can occur due to?

Answer 13

metabolism in all tissue - continuous production of CO2
breakdown of food - protein, other organic minerals etc (phosphorus and sulphur - phosphorus and sulfuric acid)
metabolic intermediaries - lactic acid in exercise

Question 14

how does the body deal with changes in pH?

Answer 14

existence of a buffering system
Bicarbonate buffer system (MAJOR SYSTEM)
The phosphate buffer system
Haemoglobin buffer system
Plasma and cell protein buffer system

Question 15

what do the kidneys regulate in order to regulate blood pH?

Answer 15

regulation of HCO3-

Question 16

what do the lungs regulate in order to regulate blood pH?

Answer 16

releasing CO2

Question 17

pathology of the resp system leads to?

Answer 17

leads to acid base imbalance

Question 18

regulation of pH by the renal system is done by?

Answer 18

done by:
reabsorbing filtered bicarbonate (HCO3-)
Synthesis of new bicarbonate (HCO3-)
Tubular secretion of H+

Question 19

describe bicarbonate reabsorption in the nephron?

Answer 19

tubular cells normally reabsorb all the filtered HCO3-
Mostly at the proximal tubule (about 80%)
Remainder in the loop of Henle and distal loop (about 20%)

Question 20

Once HCO3- is reabsorbed - what happens?

Answer 20

it is reabsorbed into the interstitial space
need to be reabsorbed back into the peritubular capillaries
occurs via Na+/HCO3- co transporters (proximal tubule)
Cl- / HCO3- exchanger (collecting tubules)

Question 21

Describe H+ secretion:

Answer 21

most excreted H+ gains entry to tubular system from being actively secreted
H+ is secreted into the tubular filtrate by the proximal, distal and collecting tubules
H+ secretion increases when pH is low (or CO2 is high) and decreases when pH is high
No mechanism of reabsorption of H+

Question 22

Describe how H+ can be secreted?

Answer 22

Electrogenic H+ pump
Na-H+ exchanger
H+ - K+ exchanger

Question 23

what is the electrogenic H+ pump?

Answer 23

ATP-driven H+ pump (CD)

Question 24

What is the Na-H+ exchanger?

Answer 24

proximal tubule, DT, CD
H+ secreted in exchange for Na+

Question 25

what is H+ - K+ exchanger?

Answer 25

electroneutral pump exchanging H+ for K+

Question 26

what is acidosis?

Answer 26

an abnormal process that produces acidaemia - low pH

Question 27

what is respiratory acidosis?

Answer 27

this is a low pH where primary defect is an increase in the pCO2

Question 28

what is metabolic acidosis?

Answer 28

this is a low pH where the primary defect is a decrease in plasma HCO3-

Question 29

what is alkolosis?

Answer 29

it is an abnormal process that produces alkalaemia - high pH

Question 30

what is respiratory alkolosis?

Answer 30

this is high pH where primary defect is a decrease in pCO2

Question 31

what is metabolic alkalosis?

Answer 31

this is high pH where primary defect is an increase in plasma HCO3-

Question 32

what is the compensatory response in respiratory acidosis?

Answer 32

pCO2 has increased and therefore blood pH has fallen SO Kidneys will attempt to bring about an increase in plasma HCO3 known as: RENAL COMPENSATION

Question 33

what is the compensatory response in metabolic acidosis?

Answer 33

Plasma HCO3- has decreased and therefore blood pH has fallen SO Lungs will increase ventilation, rate of breathing leading to a decrease in pCO2 Known as RESPIRATORY COMPENSATION

Question 34

What is the compensatory response in respiratory alkalosis?

Answer 34

pCO2 has decreased and therefore blood pH has risen SO Kidneys will decrease in H+ secretion Only some HCO3- is reabsorbed but rest excreted. Tubular synthesis of HCO3- is decreased This is RENAL COMPENSATION

Question 35

What is the compensatory response in metabolic alkalosis?

Answer 35

HCO3- has increased and therefore blood pH has increased SO Lungs will increase level of pCO2 by reducing rate of breathing and ventilation This is RESPIRATORY COMPENSATION