Acid/Base balance in the kidney

Question 1

which two organs work together to control the acid base balance in the body?

Answer 1

lungs and kidneys

Question 2

what is the normal range for plasma pH

Answer 2

7.35-7.45

Question 3

what does a change in one pH unit represent

Answer 3

10 fold change in H+ conc

Question 4

describe the concept of alkalemia and how it leads to muscle twitches and tingling

Answer 4

• albumin has severals COOH chains
• H is removed to reverse alkalosis
• negative carboxyl chain attracts the Ca
• now there is less free calcium in body as it is bound to albumin
• this increases excitability of nerves
• easier to fire an action potential
• severe = numb respiratory muscles

Question 5

describe the concept of acidemia and how it effected the excitability of neurones

Answer 5

• albumin has several COOH groups
  -less negative charges for calcium to bind to
• more free calcium in the blood
• neurones over stabilise and harder to fire an AP
• at the same time K is being swapped out for H so increased K -> arrhythmia
• more H denatures proteins

Question 6

what are some ways the body introduces acids

Answer 6

diet:
fatty acids
amino acids
metabolism:
c02
lactic acid
ketoacidosis

Question 7

what are the three buffer systems in the body?

Answer 7

• HCO3 in extracellular fluid -> manage blood pH
• proteins, haemoglobin and phosphates in cells
• sodium phosphate -> regulate intercellular pH

Question 8

what are the three ways to control the blood pH

Answer 8

1. buffers
2. ventilation
3. renal regulation of H and Hco3

Question 9

what are the two ways kidneys can alter pH

Answer 9

1. directly by excreting H
2. indirectly by changing rate at which HC03 is reabsorbed or excreted

Question 10

how are acidosis and hyperkalemia linked

Answer 10

• K inside cells will swap with H outside
• this will temporarily help with neutralising pH
• but there will be a build up of K
• can lead to heart issues

Question 11

how is alkalosis and hypokalaemia linked

Answer 11

• H inside the cell will exchange with K outside
• K will then reduce and cause hypokalaemia

Question 12

what is respiratory acidosis

Answer 12

• hypoventilation
• high C02
• compensation can must be from renal mechanisms

Question 13

what is respiratory alkalosis

Answer 13

• hyperventilation
• co2 levels drop
  -renal compensation from the kidney
• Hco3 not reabsorbed into blood
  -late DCT H reabsorbed

Question 14

what is metabolic acidosis

Answer 14

• high H levels
• due to lactic acidosis and ketoacidosis
• respiratory compensation
  -can have renal compensation

Question 15

what is the anion gap

Answer 15

difference between measured anions and cations
([na] + [K]) - ([cl] +[Hco3])
normally between 10-18

Question 16

when are there situations when the anion gap increases

Answer 16

• if Hco3 is replaced by other anions -> then its number will reduce to 0
  -metabolic acid reacts with HCo3 then the anion replaces it which doesn’t count
• if a patient is acidotic then more Hco3 is going to be used up and there will be a bigger difference between anion and cations

Question 17

what are causes of hypokalaemia

Answer 17

• renal losses -> diuretics, renal tubular acidosis, excess aldosterone
• GI losses
  -Alkalosis - hydrogen ions transported out if cells

Question 18

explain the role of NH4 in the proximal convoluted tubule

Answer 18

• when acidosis gets very extreme
• glutamine an A-A can be broken down
• it produces more HCO3
• ammonium gets produced (NH4+)
• it is charged so can’t pass through the cell to lumen
• it converts into ammonia and H
• it then leaves the cell and enters lumen of PCT
• converts back into NH4+
• stops acidosis as its alkaline

Question 19

describe the phosphate buffering system

Answer 19

• it is known as a titratable buffer
• Hp04 + H join
• this forms H2P04
• this works In conjunction with NH4 and helps reduce acidosis

Question 20

what is the role of carbonic anhydrase

Answer 20

it is an enzyme that catalyses the reaction of C02 + H20 -> HC03- + H+
it goes both ways