The role of ventilation in acid base balance

Question 1

What does pH express?

Answer 1

pH expresses concentration of H+

Question 2

Why is pH homeostasis important?

Answer 2

• 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

Question 3

Why is arterial pressure tightly regulated?

Answer 3

Arterial pH is tightly regulated to ensure effective protein function because the circulatory system innervates all organs and tissues

Question 4

How is the tight regulation of arterial pH achieved?

Answer 4

Achieved by the presence of buffering systems and by regulating the level of molecules associated with acid and base production

Question 5

What buffer is present in our circulatory system?

Answer 5

-Presence of weak acid(H2CO2) and conjugate base(HCO3-)

Question 6

What happens on addition of H+ to the bicarbonate buffer system?

Answer 6

There is an increase in [H2CO3]

Question 7

What happens when H+ is removed from the bicarbonate buffers system?

Answer 7

There is a decrease in [H2CO3]

Question 8

What happens to H+ formed by the addition of strong acid?

Answer 8

Any H+ formed by addition of strong acid react with conjugate base to form weaker acid hence pH remains relatively stable

Question 9

Why are buffers consisting of a weak acid and conjugate base used?

Answer 9

Buffers consisting of a weak acid + conjugate base are used to resist sharp changes in pH

Question 10

What does the relationship between PCO2 and [H2CO3] mean?

Answer 10

Means that CO2 transport is important in acid-base balance

Question 11

What happens in hypo-ventilation?

Answer 11

1)Accumulation of CO2
2)Increase in [H2CO3]
3)Increase in[H+]
Results in acidosis

Question 12

What happens in hyper-ventilation?

Answer 12

1)Removal of CO2
2)Decrease in [H2CO3]
3)Decrease in [H+]
Results in alkalosis

Question 13

How do the lungs and kidneys maintain blood pH homeostasis?

Answer 13

By regulating PaCO2 and [HCO3-]

Question 14

Renal regulation of HCO3-

Answer 14

Regulating reeabsorbtion/excretion in glomerular filtrate

Question 15

Respiratory regulation of PaCO2

Answer 15

Regulating ventilation

Question 16

What does an increase or a decrease in PaCO2 do?

Answer 16

Increase in PaCO2-Decrease pH

Decrease in PaCO2-Increase pH

Question 17

What does an increase or a decrease in [HCO3-] do?

Answer 17

Increase in [HCO3-]-Increases pH

Decrease in [HCO2-]-Decrease pH

Question 18

At what ph does acidosis occur and what is the problem and what is to blame?

Answer 18

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

Question 19

At what pH does alkalosis occur and what is the problem and what is to blame?

Answer 19

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

Question 20

What is an example of pH disturbance?(acidosis)

Answer 20

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

Question 21

What is an example of pH disturbance?(alkalosis)

Answer 21

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.

Question 22

What are the causes of hyperventilation?

Answer 22

Anxiety

Question 23

Steps involved in hyperventilation?

Answer 23

• Increased ventilation without increased metabolic demand
• Hyperventilation which results in decreased PaCO2
• Results in respiratory alkalosis