Acid/Base balance in the kidney Flashcards
which two organs work together to control the acid base balance in the body?
lungs and kidneys
what is the normal range for plasma pH
7.35-7.45
what does a change in one pH unit represent
10 fold change in H+ conc
describe the concept of alkalemia and how it leads to muscle twitches and tingling
- 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
describe the concept of acidemia and how it effected the excitability of neurones
- 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
what are some ways the body introduces acids
diet:
fatty acids
amino acids
metabolism:
c02
lactic acid
ketoacidosis
what are the three buffer systems in the body?
- HCO3 in extracellular fluid -> manage blood pH
- proteins, haemoglobin and phosphates in cells
- sodium phosphate -> regulate intercellular pH
what are the three ways to control the blood pH
- buffers
- ventilation
- renal regulation of H and Hco3
what are the two ways kidneys can alter pH
- directly by excreting H
- indirectly by changing rate at which HC03 is reabsorbed or excreted
how are acidosis and hyperkalemia linked
- 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
how is alkalosis and hypokalaemia linked
- H inside the cell will exchange with K outside
- K will then reduce and cause hypokalaemia
what is respiratory acidosis
- hypoventilation
- high C02
- compensation can must be from renal mechanisms
what is respiratory alkalosis
- hyperventilation
- co2 levels drop
-renal compensation from the kidney - Hco3 not reabsorbed into blood
-late DCT H reabsorbed
what is metabolic acidosis
- high H levels
- due to lactic acidosis and ketoacidosis
- respiratory compensation
-can have renal compensation
what is the anion gap
difference between measured anions and cations
([na] + [K]) - ([cl] +[Hco3])
normally between 10-18
when are there situations when the anion gap increases
- 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
what are causes of hypokalaemia
- renal losses -> diuretics, renal tubular acidosis, excess aldosterone
- GI losses
-Alkalosis - hydrogen ions transported out if cells
explain the role of NH4 in the proximal convoluted tubule
- 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
describe the phosphate buffering system
- it is known as a titratable buffer
- Hp04 + H join
- this forms H2P04
- this works In conjunction with NH4 and helps reduce acidosis
what is the role of carbonic anhydrase
it is an enzyme that catalyses the reaction of C02 + H20 -> HC03- + H+
it goes both ways
