Flashcards in Acid-Base Homeostasis Deck (52)
What are the main organs that provide outputs to maintain acid-base homeostasis? (2)
How much CO2 do you produce a day?
How much unmetabolised acids do you produce a day?
How much plasma [H+] do you produce a day?
What are the main buffering systems in the body? (6)
What is the reference range for pH?
7.35 - 7.45
What is the reference range for [H+]?
How are [H+] and pH related?
As [H+] increases, pH decreases.
What is the Henderson-Hasselbalch equation used for?
-pH as a measure of acidity
-Estimates the pH of a buffer
-Finding equilibrium pH in acid-base reactions
What are the Henderson-Hasselbalch equation?
H+ + HCO3- H2CO3 CO2 + H2O
What does [H+] homeostasis require a balance between?
Balance between H+ production and regeneration of HCO3-.
What are the main sites of acid-base metabolism in the body? (4)
How long does it take for the kidneys to alter the acid-base balance?
A couple of days.
What do RBCs take up and release when acidified?
Take up CO2, release O2.
When does a right shift occur on an O2-Hb dissociation curve?
Right shift with
Increased 2,3 dipG
What does a right shift on an O2-Hb dissociation curve mean?
RBCs cannot hold O2 as well.
-decreased SO2 at same PO2
What role does the kidney have in maintaining bicarbonate haemostasis?
Filtered by the kidneys;
-renal reclaiming (absorption by NA/H pump)
What happens at the distal tubule of the kidneys?
Endocrine control (aldosterone) >> regulates salt/water through K+/H+ exchange.
What happens during acidosis to K+ and H+ at the distal tubule of the kidney?
H+ is lost, K+ is retained.
How is acid-base homeostasis maintained in the GI tract?
-H+ excreted in stomach
-HCO3- excreted in pancreas to neutralise
How is the liver involved in acid-base metabolism? (2)
What are proteins and AAs converted to in the liver?
What does the carbon skeleton go on the form in the liver?
H+ and urea.
-inhibited by acidosis
What does NH4+ go on too form in the liver?
-stimulated by alkalosis
-excreted in urine
What is excess NH4+ produced by proteins used for?
-NH4+ and CO2 are combined to neutralise HCO3-
Is CO2 acidic or alkali when dissolved?
What pathways are blocked in severe liver failure? (2)
NH4+ + oxoglutarate >> glutamine.
NH4+ + CO2 >> urea + H+.
What are the main acid-base consequences of severe liver failure? (2)
What are the 2 types of acidosis/alkalosis?
What are the main compensatory methods for acidosis/alkalosis? (3)
-Renal bicarbonate regeneration
-Hepatic shift (urea synthesis / ammonia excretion)
Is bicarbonate (HCO3-) acidic or alkaline?
What is the normal [H+] value?
(range : 36-44)
What is the main equation involved with alkalosis/acidosis?
H+ + HCO3- >> H2CO3 >> CO2 + H2O.
What are the causes of metabolic alkalosis? (3)
-Generation of bicarbonate by gastric mucosa
-Renal generation of HCO3- in hypokalaemia
-Administration of bicarbonate
What are the main consequences of metabolic alkalosis? (3)
-K+ >> cells and urine
-PO4 >> cells
What are the main signs / symptoms of metabolic alkalosis?
What causes respiratory alkalosis?
Increased CO2 excretion due to hyperventilation.
-CO2 excretion > CO2 production
How does respiratory alkalosis typically present?
What electrolyte imbalances does respiratory alkalosis cause?
What are the main causes of respiratory acidosis? (3)
CO2 retention due to:
- inadequate ventilation
- parenchymal lung disease
- inadequate perfusion
How does respiratory acidosis typically present?
What electrolyte imbalances does respiratory acidosis cause? (3)
What are the main causes of metabolic acidosis? (4)
-Increased H+ formation
-Reduced renal H+ excretion
-Loss of bicarbonate
What are the main causes of increased H+ formation? (4)
-Inherited organic acidoses
What are the main symptoms of metabolic acidosis?
What is diabetic keto-acidosis?
Lack of insulin >>
- increased FFA
which all >> ACIDOSIS.
What are the 2 types of lactic acidosis?
-Type A - shock (decreased O2)
-Type B - metabolic / toxic causes
Does high lactate always lead to lactic acidosis?
No, not in alkalosis.
>> increased glycolysis and vasoconstriction
What causes reduced H+ excretion? (2)
-Renal tubular acidosis
-Generalised renal failure
How does renal failure cause reduced H+ excretion?
REDUCED VOLUME OF NEPHRONS;
-increased HCO3- loss
-reduced NH4+ secretion
-NH4+ is needed by liver for urea and H+ synthesis
What else is H+ derived from apart from NH4+?
-only a very small fraction