The role of ventilation in acid base balance Flashcards
What does pH express?
pH expresses concentration of H+
Why is pH homeostasis important?
- Protein function depends on specific secondary, tertiary and Quaternary structures achieved via inter and intra chain bonding
- Various factors can denature proteins, by disrupting these bonds thus impairing function
Why is arterial pressure tightly regulated?
Arterial pH is tightly regulated to ensure effective protein function because the circulatory system innervates all organs and tissues
How is the tight regulation of arterial pH achieved?
Achieved by the presence of buffering systems and by regulating the level of molecules associated with acid and base production
What buffer is present in our circulatory system?
-Presence of weak acid(H2CO2) and conjugate base(HCO3-)
What happens on addition of H+ to the bicarbonate buffer system?
There is an increase in [H2CO3]
What happens when H+ is removed from the bicarbonate buffers system?
There is a decrease in [H2CO3]
What happens to H+ formed by the addition of strong acid?
Any H+ formed by addition of strong acid react with conjugate base to form weaker acid hence pH remains relatively stable
Why are buffers consisting of a weak acid and conjugate base used?
Buffers consisting of a weak acid + conjugate base are used to resist sharp changes in pH
What does the relationship between PCO2 and [H2CO3] mean?
Means that CO2 transport is important in acid-base balance
What happens in hypo-ventilation?
1)Accumulation of CO2
2)Increase in [H2CO3]
3)Increase in[H+]
Results in acidosis
What happens in hyper-ventilation?
1)Removal of CO2
2)Decrease in [H2CO3]
3)Decrease in [H+]
Results in alkalosis
How do the lungs and kidneys maintain blood pH homeostasis?
By regulating PaCO2 and [HCO3-]
Renal regulation of HCO3-
Regulating reeabsorbtion/excretion in glomerular filtrate
Respiratory regulation of PaCO2
Regulating ventilation
What does an increase or a decrease in PaCO2 do?
Increase in PaCO2-Decrease pH
Decrease in PaCO2-Increase pH
What does an increase or a decrease in [HCO3-] do?
Increase in [HCO3-]-Increases pH
Decrease in [HCO2-]-Decrease pH
At what ph does acidosis occur and what is the problem and what is to blame?
Occurs at pH<7.35
The problem is acidosis:
-CO2 is high Or,
-HCO3- is low
If CO2 is high then its respiratory acidosis
If HCO3- is low then its metabolic acidosis
At what pH does alkalosis occur and what is the problem and what is to blame?
Occurs at pH>7.45
The problem is alkalosis:
-CO2 is low Or,
-HCO3- is high
If CO2 is low then its respiratory alkalosis
If HCO3- is high then its metabolic alkalosis
What is an example of pH disturbance?(acidosis)
Acidosis induced hyperkalaemia:
1) Increase in extracellular [H+]
2) This results in a decreased [H+}concentration gradient
3) There’s a decrease H+ excretion, which results in a decrease in H+-Na+ exchange and a decrease in Na+-K+ exchange
4) There’s a decrease in Na+-K+ exchange which leads to a decrease in K+ absorption
5) There’s an accumulation of K+ in serum leading to hyperkalaemia
6) This causes cardiac arrhythmia and muscle weakness
What is an example of pH disturbance?(alkalosis)
1) CO2 acts as vasodilators in blood vessels
2) Hyperventilation decreases CO2 and H+ leading to alkalosis
3) Alkalosis causes vasoconstriction of cerebral arteries
4) There’s a decrease in cerebral blood flow causing headaches, confusion etc.
What are the causes of hyperventilation?
Anxiety
Steps involved in hyperventilation?
- Increased ventilation without increased metabolic demand
- Hyperventilation which results in decreased PaCO2
- Results in respiratory alkalosis
