Acidosis and acid-base regulation

Question 1

Define an acid and give an exampl

Answer 1

• A molecule that is capable of donating hydrogen ions

Question 2

Define a base

Answer 2

A molecule which can accept hydrogen ions

Question 3

What is the normal pH of arterial blood?

Answer 3

7.4

Question 4

What is the normal pH of venous blood?

Answer 4

7.35

Question 5

What terms are given to arterial blood that falls below pH 7.4?

Answer 5

Acidosis

Question 6

Hydrogen ion control is tightly regulated. What are the 3 ways in the body defends against changes in hydrogen ion concentration

Answer 6

1. Formation of acids or bases in order to prevent excessive changes of hydorgen ion concentration - they don’t eliminate hydrogen, essentially sequester them until the levels is back to normal
2. Respiratory center, which takes information from chemoreceptors and looks at Co2 levels in particular, and alters breathing rate to compensate
3. Kidneys can alter the secretion of hydrogen and bicarbonate
4. Red blood cells can produce 2,3 biphosphoglycerate when oxyhemoglobin level saturation is low, and reduces hemoglobin affinity for oxygen

Question 7

Red blood cell protein HEMOGLOBIN is an important intracellular buffer. Explain how it can work to compensate when acidosis occurs

Answer 7

Hemoglobin binds hydrogen ions more effectively when PO2 is low, and the more hydrogen is bound the LESSER AFFINITY hemoglobin has for oxygen. The subsequent lowered affinity for oxygen is balanced by an INCREASE in affinity for carbon dioxide.

Question 8

After all the buffer stuff, the second line of control against acid-base disturbances is control of ventilation by the lungs. An increase in ventilation eliminates carbon dioxide , which therefore will reduce its eventual conversion to Hydrogen.

Answer 8

Exercise will increase the rate of ventilation.

Question 9

Increased hydrogen ion concentration stimulates alveolar ventilation Explain at a basic level how the respiratory centres might respond to changes in PH

Answer 9

If hydrogen ion concentration increases, respiratory system is stimulated and alveolar ventilation INCREASES

If hydrogen ions decrease, respiratory system is inhibited and alveolar ventilation decreases.

Question 10

Where does seceretion of hydrogen and reabsorption of bicarbonate primarily occur?

Answer 10

Proximal convoluted tubule

Question 11

impairment of lung function can cause respiratory acidosis

Answer 11

• In something like emphysema, there is a decreased ability of the alveoli to eliminate CO2, which causes a buildup of CO2 and means there is a tendency towards towards acidosis.

Question 12

How do you know the difference between metabolic and respiratory acidosis?

Answer 12

Respiratory is due to excess CO2 as a result of respiratory impairment

Metabolic is due to acidosis that is not a result of excess of CO2.