Regulation of Homeostasis by the Kidney: Acid-Base Balance

Question 1

What is the Henderson-Hasselbalch equation?

Answer 1

The Henderson-Hasselbalch equation is pH = pKa + log ([A-]/[HA]).

Question 2

What is the equilibrium involving CO2, H2O, H2CO3, and HCO3-?

Answer 2

CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+.

Question 3

What does pH represent in the Henderson-Hasselbalch equation?

Answer 3

pH represents the acidity or alkalinity of a solution.

Question 4

What is the role of the kidney in pH regulation?

Answer 4

The kidney regulates pH by reabsorbing or excreting bicarbonate ions (HCO3-) and hydrogen ions (H+).

Question 5

What is the role of the lung in pH regulation?

Answer 5

The lung regulates pH by controlling the elimination of carbon dioxide (CO2), which affects the levels of carbonic acid (H2CO3) and bicarbonate ions (HCO3-).

Question 6

What is the importance of pH control in the body?

Answer 6

pH control is important for maintaining homeostasis. The extracellular fluid (ECF) pH should be kept between 7.35 and 7.45. Deviations outside this range can lead to acidosis (acidaemia) or alkalosis (alkalaemia), affecting various body systems and potentially leading to severe complications.

Question 7

What are the potential consequences of pH alterations outside the normal range?

Answer 7

pH alterations outside the normal range can result in coma, cardiac failure, circulatory collapse, and in extreme cases, death. Severe acidosis (pH < 6.8) or alkalosis (pH > 8.0) can be life-threatening.

Question 8

What are the sources of acid generation in the body?

Answer 8

The sources of acid generation include carbolic (volatile) acids, which are produced from the metabolism of carbohydrates and fats, and non-carbolic (non-volatile) acids, which are generated from the metabolism of sulfur-containing amino acids.

Question 9

How are carbolic acids eliminated from the body?

Answer 9

Carbolic acids are converted to CO2, which is eliminated by the lungs through the excretion of CO2.

Question 10

How are non-carbolic acids eliminated from the body?

Answer 10

Non-carbolic acids are buffered with bicarbonate (HCO3-) before being eliminated by the kidneys through the excretion of H+.

Question 11

What are the mechanisms involved in dealing with the acid (H+) load in the body?

Answer 11

The mechanisms include buffering with bicarbonate and HPO42-, elimination through increased respiratory drive to excrete CO2, and increased hydrogen ion secretion by the kidneys.

Question 12

How does the renal system contribute to fluid and acid-base homeostasis?

Answer 12

The renal system plays a role in maintaining acid-base balance by secreting hydrogen ions and reabsorbing or excreting bicarbonate ions. It also helps control blood pressure, ECF osmolality, and fluid balance.

Question 13

How does the cardiovascular system contribute to fluid and acid-base homeostasis?

Answer 13

The cardiovascular system helps maintain effective circulating volume, perfusion, and blood pressure, which are important for fluid and acid-base balance.

Question 14

How does the respiratory system contribute to fluid and acid-base homeostasis?

Answer 14

The respiratory system plays a role in gas exchange and can adjust the respiratory rate to increase or decrease CO2 excretion, thereby helping regulate acid-base balance.

Question 15

What is the purpose of homeostasis in relation to fluid and acid-base balance?

Answer 15

Homeostasis is the body’s ability to maintain stable conditions within a narrow range. It ensures that fluid and acid-base balance are kept within the appropriate limits for optimal physiological function.

Question 16

Which parts of the nephron are involved in the renal excretion of acid load?

Answer 16

The proximal convoluted tubule and the intercalated cells of the cortical collecting ducts are the main sites involved in the renal excretion of acid load.

Question 17

What is the most prevalent filtered buffer in the distal nephron when urinary pH is less than 5.8?

Answer 17

HPO4-2 (dihydrogen phosphate) is the most prevalent filtered buffer in the distal nephron when urinary pH is less than 5.8.

Question 18

What is the major adaptive response to acid load in terms of ammonium excretion?

Answer 18

Ammonium excretion, both in the proximal collecting ducts and through direct diffusion of lipid-soluble ammonia, constitutes a major adaptive response to acid load.

Question 19

How does a decrease in extracellular bicarbonate affect the tubular cellular pH?

Answer 19

A decrease in extracellular bicarbonate increases the gradient across the basolateral membrane for bicarbonate diffusion out of the cell, thereby lowering the tubular cellular pH.

Question 20

What are the causes of metabolic acidosis (increased H+ concentration)?

Answer 20

Metabolic acidosis can be caused by loss of bicarbonate, diarrhea, diuretic therapy, ingestion of acid (such as aspirin, ethylene glycol, or methanol), endogenous acid production (such as lactic acidosis or ketoacidosis), and decreased acid excretion due to renal failure.

Question 21

What are the causes of metabolic alkalosis (increased HCO3- concentration)?

Answer 21

Metabolic alkalosis can be caused by the loss of acid, such as through vomiting or loss of stomach acid.

Question 22

What are the causes of respiratory acidosis (increased CO2 concentration)?

Answer 22

Chronic lung diseases such as COPD (Chronic Obstructive Pulmonary Disease) and pulmonary fibrosis can cause respiratory acidosis.

Question 23

What are the causes of respiratory alkalosis (reduced CO2 concentration)?

Answer 23

Hyperventilation, which can be caused by factors such as anxiety or pneumonia, can lead to respiratory alkalosis.

Question 24

What is a specific example of a condition causing respiratory alkalosis?

Answer 24

Acute bronchial asthma can lead to respiratory alkalosis.

Question 25

What is the primary abnormality and compensatory response in metabolic acidosis?

Answer 25

Primary abnormality: Rise in plasma acid concentration.
Compensatory response: Hyperventilation, renal hydrogen excretion, and buffering of acid in extracellular fluid, cells, and bones.

Question 26

What is the primary abnormality and compensatory response in metabolic alkalosis?

Answer 26

Primary abnormality: Rise in plasma bicarbonate concentration.
Compensatory response: Hyperventilation, renal hydrogen excretion, and buffering.

Question 27

What is the primary abnormality and compensatory response in respiratory acidosis?

Answer 27

Primary abnormality: Elevation in CO2 (carbon dioxide).
Compensatory response: Hypoventilation, reduced renal hydrogen excretion, and reduced bicarbonate reabsorption.

Question 28

What is the primary abnormality and compensatory response in respiratory alkalosis?

Answer 28

Primary abnormality: Reduction in CO2 (carbon dioxide).
Compensatory response: Hyperventilation, reduced renal hydrogen excretion, and increased renal bicarbonate reabsorption.

Question 29

What are the cation shifts during metabolic acidosis and metabolic alkalosis?

Answer 29

Metabolic acidosis: Frequently associated with hyperkalemia (high K+).
Metabolic alkalosis: Associated with hypokalemia (low K+).

Question 30

What is the treatment for metabolic acidosis?

Answer 30

The treatment for metabolic acidosis includes IV sodium bicarbonate 2.7% (especially useful if the patient is volume depleted), IV furosemide (especially useful if the patient is passing urine and is volume replete), and dialysis. The underlying cause should also be addressed.

Question 31

What is the treatment for metabolic alkalosis?

Answer 31

The treatment for metabolic alkalosis involves administering IV sodium/potassium chloride. Treating the underlying cause is also important.

Question 32

What is the treatment for respiratory acidosis?

Answer 32

The treatment for respiratory acidosis involves ventilation support, which may include mechanical ventilation. Treating the underlying cause is also necessary.

Question 33

What is the treatment for respiratory alkalosis?

Answer 33

Breathing into a paper bag can be helpful for patients experiencing hyperventilation-induced respiratory alkalosis. Treating the underlying cause is essential as well.

Question 34

How do the renal system, cardiovascular system, and respiratory system work together to maintain acid-base homeostasis?

Answer 34

The renal, cardiovascular, and respiratory systems closely interact to maintain acid-base balance and homeostasis. The renal system regulates hydrogen ion excretion and bicarbonate reabsorption, the cardiovascular system ensures proper perfusion and blood pressure, and the respiratory system controls gas exchange. All three systems constantly adjust and respond to changes to maintain balance and homeostasis.