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Questions and Answers
Which of the following statements is TRUE regarding the regulation of acid-base balance in the body?
Which of the following statements is TRUE regarding the regulation of acid-base balance in the body?
- The most powerful acid-base regulatory systems operate over a period of minutes.
- The pH of urine can vary significantly depending on the acid-base status of the extracellular fluid. (correct)
- Hypoxia and poor blood flow can lead to an accumulation of acids in the body. (correct)
- The kidneys play a minor role in correcting abnormalities of extracellular fluid H+ concentration.
What is the general form of the buffering reaction in the body fluids?
What is the general form of the buffering reaction in the body fluids?
- Buffer - H+ ⇌ H Buffer
- Buffer + H+ ⇌ H Buffer (correct)
- Buffer + H2O ⇌ H Buffer
- Buffer + OH- ⇌ H Buffer
What happens to the buffering reaction when the H+ concentration increases?
What happens to the buffering reaction when the H+ concentration increases?
- The reaction shifts to the right, and less H+ binds to the buffer.
- The reaction shifts to the left, and more H+ binds to the buffer.
- The reaction shifts to the right, and more H+ binds to the buffer. (correct)
- The reaction remains unchanged, as the buffer is already saturated.
What is the role of a buffer in the body fluids?
What is the role of a buffer in the body fluids?
What is an example of a situation that could cause acid accumulation and decreased intracellular pH?
What is an example of a situation that could cause acid accumulation and decreased intracellular pH?
What does the term "acidosis" describe?
What does the term "acidosis" describe?
What is the normal pH range of extracellular fluids?
What is the normal pH range of extracellular fluids?
What is the primary role of the kidneys in regulating acid-base balance?
What is the primary role of the kidneys in regulating acid-base balance?
What happens to the partial pressure of carbon dioxide (PCO2) in the extracellular fluid when the rate of metabolic formation of CO2 increases?
What happens to the partial pressure of carbon dioxide (PCO2) in the extracellular fluid when the rate of metabolic formation of CO2 increases?
How does an increased rate of pulmonary ventilation affect the PCO2 in the extracellular fluid?
How does an increased rate of pulmonary ventilation affect the PCO2 in the extracellular fluid?
Which buffer system is considered MOST important in managing acid-base balance?
Which buffer system is considered MOST important in managing acid-base balance?
What is the normal range of pH for the extracellular fluid?
What is the normal range of pH for the extracellular fluid?
Under what specific condition does the kidney generate new HCO3−?
Under what specific condition does the kidney generate new HCO3−?
A decrease in pH from 7.4 to 7.0 causes what change in alveolar ventilation rate?
A decrease in pH from 7.4 to 7.0 causes what change in alveolar ventilation rate?
What happens to the ventilation rate when plasma pH rises above 7.4?
What happens to the ventilation rate when plasma pH rises above 7.4?
Where in the nephron do the Type A intercalated cells primarily function?
Where in the nephron do the Type A intercalated cells primarily function?
What is the direct consequence of H+ secretion in Type A intercalated cells?
What is the direct consequence of H+ secretion in Type A intercalated cells?
How does the body's response to changes in pH differ at reduced versus increased levels of pH?
How does the body's response to changes in pH differ at reduced versus increased levels of pH?
What is the primary mechanism responsible for the movement of H+ out of Type A intercalated cells?
What is the primary mechanism responsible for the movement of H+ out of Type A intercalated cells?
What is the timeframe for the respiratory system to return the pH to approximately 7.2 to 7.3 after a significant decrease in pH?
What is the timeframe for the respiratory system to return the pH to approximately 7.2 to 7.3 after a significant decrease in pH?
What role does alveolar ventilation play in regulating the pH of body fluids?
What role does alveolar ventilation play in regulating the pH of body fluids?
What is the ratio of HCO3− reabsorbed to H+ secreted in the Type A intercalated cells during normal conditions?
What is the ratio of HCO3− reabsorbed to H+ secreted in the Type A intercalated cells during normal conditions?
In the context of acid-base balance, what is the specific role of the ammonia buffer in the kidney?
In the context of acid-base balance, what is the specific role of the ammonia buffer in the kidney?
When looking at the overall process of H+ secretion in the kidney, what is the net effect on the blood pH?
When looking at the overall process of H+ secretion in the kidney, what is the net effect on the blood pH?
What does the isohydric principle state?
What does the isohydric principle state?
What happens to all buffer systems in the body when there is a change in H+ concentration in the extracellular fluid?
What happens to all buffer systems in the body when there is a change in H+ concentration in the extracellular fluid?
Given the formula for the isohydric principle: H+ = K1 × A1/HA1 = K2 × A2/HA2 = K3 × A3/HA3, what do K1, K2, and K3 represent?
Given the formula for the isohydric principle: H+ = K1 × A1/HA1 = K2 × A2/HA2 = K3 × A3/HA3, what do K1, K2, and K3 represent?
What happens to the extracellular fluid pH when the rate of alveolar ventilation increases?
What happens to the extracellular fluid pH when the rate of alveolar ventilation increases?
What is the primary factor that affects PCO2 in the extracellular fluid, assuming metabolic CO2 formation remains constant?
What is the primary factor that affects PCO2 in the extracellular fluid, assuming metabolic CO2 formation remains constant?
How does an increase in alveolar ventilation affect the balance of the buffer systems in the body?
How does an increase in alveolar ventilation affect the balance of the buffer systems in the body?
Why is the isohydric principle important for maintaining acid-base balance in the body?
Why is the isohydric principle important for maintaining acid-base balance in the body?
Which of the following factors can influence the balance of the buffer systems in the body?
Which of the following factors can influence the balance of the buffer systems in the body?
What is the primary role of bicarbonate (HCO3-) in the renal tubular lumen?
What is the primary role of bicarbonate (HCO3-) in the renal tubular lumen?
What is the role of the enzyme carbonic anhydrase in the process of acid-base regulation by the kidney?
What is the role of the enzyme carbonic anhydrase in the process of acid-base regulation by the kidney?
Which of the following is TRUE about the process of ammonium ion (NH4+) production and secretion by proximal tubular cells?
Which of the following is TRUE about the process of ammonium ion (NH4+) production and secretion by proximal tubular cells?
How does filtered phosphate (NaHPO4) contribute to buffering secreted H+ in the renal tubular lumen?
How does filtered phosphate (NaHPO4) contribute to buffering secreted H+ in the renal tubular lumen?
Which of the following statements correctly describes the role of sodium ions (Na+) in the renal tubular lumen during H+ secretion?
Which of the following statements correctly describes the role of sodium ions (Na+) in the renal tubular lumen during H+ secretion?
What is the primary mechanism by which the kidney eliminates excess H+?
What is the primary mechanism by which the kidney eliminates excess H+?
How does the kidney regulate blood pH?
How does the kidney regulate blood pH?
What happens to the bicarbonate (HCO3-) produced during glutamine metabolism in proximal tubular cells?
What happens to the bicarbonate (HCO3-) produced during glutamine metabolism in proximal tubular cells?
What is the primary source of glutamine used in the renal ammonium-ammonia buffer system?
What is the primary source of glutamine used in the renal ammonium-ammonia buffer system?
What happens to the NH4+ that is generated in the proximal tubules?
What happens to the NH4+ that is generated in the proximal tubules?
How does an increase in extracellular fluid H+ concentration impact the renal ammonium-ammonia buffer system?
How does an increase in extracellular fluid H+ concentration impact the renal ammonium-ammonia buffer system?
What is the mechanism by which NH4+ is excreted in the collecting tubules?
What is the mechanism by which NH4+ is excreted in the collecting tubules?
What is the net effect on the body fluids for every molecule of glutamine metabolized in the proximal tubules?
What is the net effect on the body fluids for every molecule of glutamine metabolized in the proximal tubules?
Which of the following is NOT a direct consequence of chronic acidosis?
Which of the following is NOT a direct consequence of chronic acidosis?
What is the primary role of the renal ammonium-ammonia buffer system in maintaining acid-base balance?
What is the primary role of the renal ammonium-ammonia buffer system in maintaining acid-base balance?
Why is the loss of HCO3− considered the same as the addition of H+ to the blood?
Why is the loss of HCO3− considered the same as the addition of H+ to the blood?
Flashcards
Isohydric Principle
Isohydric Principle
All buffers in a common solution equilibrate at the same H+ concentration.
Buffer Systems
Buffer Systems
Chemical systems that help maintain pH by neutralizing acids and bases.
H+ Concentration
H+ Concentration
The amount of hydrogen ions in a solution, influencing acidity.
Extracellular Fluid
Extracellular Fluid
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Dissociation Constants (K1, K2, K3)
Dissociation Constants (K1, K2, K3)
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Alveolar Ventilation
Alveolar Ventilation
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Effect on pH by Ventilation
Effect on pH by Ventilation
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Acid-Base Balance
Acid-Base Balance
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Acidosis
Acidosis
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Alkalosis
Alkalosis
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Buffering
Buffering
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pH Range of Urine
pH Range of Urine
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Role of Kidneys
Role of Kidneys
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H+ Bind Reaction
H+ Bind Reaction
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Intracellular Fluid H+ Concentration
Intracellular Fluid H+ Concentration
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Acidemia
Acidemia
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Metabolic CO2 Formation
Metabolic CO2 Formation
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Pco2
Pco2
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pH Levels
pH Levels
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Response Time for pH Adjustment
Response Time for pH Adjustment
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Effect of Increased H+ on Ventilation
Effect of Increased H+ on Ventilation
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Pulmonary Ventilation
Pulmonary Ventilation
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Phosphate buffer
Phosphate buffer
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Type A intercalated cells
Type A intercalated cells
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H+ secretion
H+ secretion
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HCO3− reabsorption
HCO3− reabsorption
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Hydrogen-potassium-ATPase
Hydrogen-potassium-ATPase
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Excess H+ in tubular fluid
Excess H+ in tubular fluid
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Ammonia buffer
Ammonia buffer
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Cl− secretion
Cl− secretion
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Ammonia Buffer System
Ammonia Buffer System
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Glutamine Metabolism
Glutamine Metabolism
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Proximal Tubules
Proximal Tubules
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Chronic Acidosis
Chronic Acidosis
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Counter-Transport Mechanism
Counter-Transport Mechanism
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Physiological Control
Physiological Control
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Buffering of H+
Buffering of H+
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Role of Glutamine
Role of Glutamine
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Secreted NH4+
Secreted NH4+
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Excretion of H+
Excretion of H+
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Sodium-Ammonium Exchange
Sodium-Ammonium Exchange
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Production of HCO3−
Production of HCO3−
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Carbonic Anhydrase
Carbonic Anhydrase
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Role of Na+
Role of Na+
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Study Notes
Acid-Base Regulation
- Hydrogen ion (H+) balance regulation is similar to other ion regulation in the body. Precise H+ regulation is crucial due to its impact on nearly all enzyme systems in the body. Extracellular fluid (ECF) H+ concentration is typically low, with a normal level of 0.00004 mEq/L. Variations are minimal compared to other ions.
Acids and Bases
- A hydrogen ion is a single proton.
- Acids release H+ in solution (e.g., HCl, ionizing into H+ and Cl-). Carbonic acid (H2CO3) forms H+ and bicarbonate (HCO3-).
- Bases accept H+. Bicarbonate (HCO3-), and proteins (e.g., hemoglobin) are key body bases. Alkalosis is excess H+ removal; acidosis is excess H+ addition.
Strong and Weak Acids/Bases
- Strong acids (e.g., HCl) fully dissociate, releasing large amounts of H+ quickly. Weak acids (e.g., H2CO3) dissociate less readily. Strong bases (e.g., OH-) strongly bind H+ effectively, while weak bases (e.g., HCO3-) bind H+ less powerfully. Most acids/bases in ECF are weak.
Normal H+ Concentration and pH
- Blood H+ concentration is tightly controlled near a normal value of 0.00004 mEq/L or pH 7.4.
- Acidemia is a blood pH below 7.4, while alkalemia is above 7.4.
Buffering Systems
- Buffers resist H+ changes by reversibly binding H+. The most important ECF buffer is the bicarbonate buffer system.
- This system comprises carbonic acid (H2CO3) and bicarbonate (HCO3-).
- An increase in H+ leads to more H2CO3 formation and CO2 release, and the reverse happens when H+ is reduced.
Acid-Base Regulation Defense Mechanisms
- The main systems defending against H+ changes are: buffers (react within seconds), the respiratory center (regulates CO2 elimination within minutes), and the kidneys (adjust acid/base excretion over hours/days).
- Buffer systems minimize H+ changes while the respiratory center eliminates CO2 (and thereby H2CO3), delaying the need for renal compensation.
Bicarbonate Buffer System
- CO2+H2O ↔ H2CO3 ↔ H+ + HCO3- maintains balance.
- If strong acid (e.g., HCl) is added, the increased H+ combines with HCO3-, forming more H2CO3, and leading to higher CO2 production and increased respiratory rate. The opposite occurs when a strong base is added.
Phosphate Buffer System
- H2PO4- ↔ H+ + HPO42- acts as an intracellular and renal tubule buffer.
- It is less important relative to bicarbonate for ECF.
Protein Buffers
- Proteins are important intracellular buffers due to their high concentrations. Hemoglobin in red blood cells is influential. Intracellular pH changes usually reflect ECF changes; however, exchanges take time.
Pulmonary Ventilation and Acid-Base Balance.
- CO2 production is continuously balanced by its expulsion via respiration.
- Increased ventilation reduces PCO2 lowering H+ concentration; vice versa.
Renal Acid-Base Balance
- Kidneys regulate acid-base balance by excreting acidic or basic urine altering H+ concentration in extracellular fluid (ECF)
- H+ secretion and HCO3- reabsorption occur in tubules, not the descending or ascending thin limbs of the Loop of Henle.
H+ Secretion and HCO3- Reabsorption: (Renal System)
- 80-90% of HCO3- reabsorption occurs in proximal tubules, supporting H+ secretion.
- Na+-H+ exchange in proximal tubules, thick ascending loop of Henle, and early distal tubule supports H+ secretion with energy from Na+ gradient, derived from Na+-K+ ATPase pumps.
- Late distal and collecting tubules employ primary active transport of H+ (using H+-ATPase or H+-K+-ATPase).
- This process allows for greater urine acidity.
Excess H+ and Ammonia Buffer System
- Excess H+ is buffered via ammonia, in the form of NH4+. The ammonia buffer system is important in generating new HCO3-, aiding ECF HCO3- replenishment during acidosis.
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