Question

Acid-Base Balance

As the rate of H+ and/or PCO2 production changes in the body, what “system” acts the quickest to stabilize pH and minimize the magnitude of such changes?

Give 3 examples of substances that comprise this “system”.

Why does the blood pH change when the blood PCO2 is changed? (you should know the chemical equation that describes this relationship)

Give an example of the kind of physiological change that would CAUSE an increase in PCO2.

What would such a condition be called?

Give an example of the kind of physiological change that would CAUSE a decrease in PCO2.

What would such a condition be called?

As PCO2 of the blood decreases, what happens to the urine H+ concentration as kidneys compensate for this change? (increase, decrease, or no change)

Explain what the kidneys are doing that makes the H+ concentration change in this manner, and how this change acts as a compensation to the decreasing PCO2.

As PCO2 of the blood decreases, what happens to the urine HCO3- concentration?

Explain what the kidneys are doing that makes the HCO3- concentration change in this manner, and how this change acts as a compensation to the decreasing PCO2.

Give an example of the kind of physiological change that would CAUSE a decrease in [H+] DIRECTLY (without causing a change in PCO2 first).

What would such a condition be called?

Give an example of the kind of physiological change that would CAUSE an increase in [H+] DIRECTLY (without causing a change in PCO2 first).

What would such a condition be called?

If the root cause of the H+ concentration changes is an abnormality of the kidneys, how might the respiratory system respond to:

a. an increasing H+ concentration.

b. a decrease in H+ concentration.

Answer 1

1. As the rate of H+ and/or PCO2 production changes in the body, what “system” acts the quickest to stabilize pH and minimize the magnitude of such changes.

Answer: Buffer system.

Rise in H+ causes lowering of pH or acidosis which can be compensated by bicobonate ions. Carbonic acid-bicarbonate buffering system and functioning of kidney play role in compensating H+ ions. Similarly CO2 production also fluctute the pH of blood by involving in bicarbonate buffering system.

2. Give 3 examples of substances that comprise this “system”.

Buffer system in blood plasma composed of:

• Plasma proteins -
• Phosphate
• Bicarbonate and carbonic acid buffers.

Aminoacids build upto form proteins that contains positively charged amino groups and negatively charged carboxyl groups which can bind to hydrogen and hydroxyl ions and by act as buffers.

The two forms of phosphates are:

A weak acid - sodium dihydrogen phosphate (Na2H2PO4−) and

A weak base - sodium monohydrogen phosphate (Na2HPO42-).

3. Why does the blood pH change when the blood PCO2 is changed? (you should know the chemical equation that describes this relationship)

When the ratio of  arterial bicarbonate to arterial PCO2 is low, which leads to acidosis. High pCO2 is associated with espiratory acidosis and low pCO2 causes respiratory alkalosis. Level of CO2 defines hypercapnea or hypoventilation when there is elevated CO2 and low CO2 is called as hypocapnea or hyperventilation. Rise in PCO2 as a result of bicarbonate ions.

NaHCO3 + HCl →  H2CO3+NaCl

H2CO3 + NaOH→HCO3- + H2O

When sodium carbonate acts with strong acid like HCL gives carbonic acid which is a weak acid which in turn acts with strong base like NaOH gives bicarbonate ion.

The expiration level of CO2 controls the level of carbonic acid. The bicarbonate level is regulated by the renal system.

4. Give an example of the kind of physiological change that would CAUSE an increase in PCO2.

Physiological condition that cause increase in pCO2:

• Hypoventilation
• Consciousness fluctuation.
• Lung disease

What would such a condition be called?

Hyercapnea.

Hypercapnea is the condition of high level of CO2 in blood arises due to hypoventilation.

Give an example of the kind of physiological change that would CAUSE a decrease in PCO2.

Answer: Hyperventilation

Hyperventialtion is the increased respiratory rate results in decreased pCO2 and lower concentration of CO2 in blood.

What would such a condition be called?

Hypocapnea.

Hypocapnea is decreased CO2 concentration in blood when there is increased vventilation. During anesthesia, decreased CO2 production without increased ventilation results in decreased pCO2 in the state called respiratory alkalosis.