Podcast
Questions and Answers
What is the normal pH of arterial blood?
What is the normal pH of arterial blood?
7.4
What is the normal variation of pH in arterial blood?
What is the normal variation of pH in arterial blood?
7.35 - 7.45
Which of the following is NOT a major buffer system in the body?
Which of the following is NOT a major buffer system in the body?
Which of the following conditions leads to a decrease in arterial Pco₂?
Which of the following conditions leads to a decrease in arterial Pco₂?
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The Henderson-Hasselbalch equation shows that the pH of blood can be determined by which two factors?
The Henderson-Hasselbalch equation shows that the pH of blood can be determined by which two factors?
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In metabolic acidosis, the kidneys excrete more H+ than normal.
In metabolic acidosis, the kidneys excrete more H+ than normal.
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Which type of acid is primarily produced by the metabolism of carbohydrates and fats?
Which type of acid is primarily produced by the metabolism of carbohydrates and fats?
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The respiratory system is the primary mechanism for eliminating excess H+ from the body fluids.
The respiratory system is the primary mechanism for eliminating excess H+ from the body fluids.
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What is the function of the Na-H+ exchanger (NHE) in the kidneys?
What is the function of the Na-H+ exchanger (NHE) in the kidneys?
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Hyperkalemia can lead to metabolic acidosis.
Hyperkalemia can lead to metabolic acidosis.
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Which of the following is NOT a cause of metabolic alkalosis?
Which of the following is NOT a cause of metabolic alkalosis?
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The buildup of which substance in the blood is a hallmark of diabetic ketoacidosis (DKA)?
The buildup of which substance in the blood is a hallmark of diabetic ketoacidosis (DKA)?
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Chronic kidney disease can lead to metabolic acidosis due to impaired excretion of phosphates and ammonia.
Chronic kidney disease can lead to metabolic acidosis due to impaired excretion of phosphates and ammonia.
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What is the most common cause of metabolic acidosis?
What is the most common cause of metabolic acidosis?
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The primary event in respiratory acidosis is an increase in PCO₂.
The primary event in respiratory acidosis is an increase in PCO₂.
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What is the compensatory response in metabolic acidosis?
What is the compensatory response in metabolic acidosis?
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Metabolic alkalosis is more common than metabolic acidosis.
Metabolic alkalosis is more common than metabolic acidosis.
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Mixed acid-base disorders involve two or more primary events influencing the acid-base status simultaneously.
Mixed acid-base disorders involve two or more primary events influencing the acid-base status simultaneously.
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Study Notes
Acid-Base Balance
- The normal pH range in the body is 7.35 - 7.45
- This range is crucial for life
- A difference of ±0.05 from 7.4 is significant,
- Large deviations from normal range are life-threatening
- About 80 mEq of H+ are produced each day through ingestion and metabolism
- There are two principle buffering systems in the body, respiratory and renal.
- The respiratory system controls CO2 and therefore carbonic acid levels.
- The renal system controls bicarbonate reabsorption
Acid and Bases:
- Strong acids: HCl → H+ + Cl-
- Strong bases: NaOH → Na+ + OH-
- Buffers: Hbase H+ + base(Weak acid/base)
- Example Buffer system: H2CO3 ⇌ H+ + HCO3− (carbonic acid and bicarbonate)
pH and H+ Concentration in Body Fluids
- Arterial blood pH: 7.40
- Venous blood pH: 7.35
- Interstitial fluid pH: 7.35
- Intracellular fluid pH range: 6.0-7.4
- Urine pH range: 4.5 - 8.0
- Gastric HCl pH: 0.8
- H+ concentration in these fluids in units of nM (nanomoles/L)
Buffer Systems
- Bicarbonate: the most important buffer in ECF
- Phosphate: not important in body fluids
- Ammonia:Major role in establishing urine pH
- Proteins: 60-70% of buffering in body fluids
- Hemoglobin (in RBC): buffers CO2
Intracellular Buffering:
- Proteins within cells provide significant buffering capacity
- H+ and HCO3- only slightly diffuse into cells
- CO2 diffuses rapidly into cells
- ICF responds to changes in ECF pH
- RBCs use hemoglobin as a buffer; CO2 reacts with water to form carbonic acid, which then dissociates into H+ and HCO3−
Bicarbonate System
- H+ + HCO3− ⇌ CO2 + H2O
- Kidneys regulate HCO3− through H+ excretion
- Lungs regulate pCO2 through alveolar ventilation
Henderson-Hasselbalch Equation
- pH = 6.1 + log ([HCO3-] / (0.03 x Pco2 ))
- This equation demonstrates the relative contributions of bicarbonate and pCO2 in determining pH
Clinical Diagnosis of Acid-Base Disorders
- Three primary variables measured to diagnose acid-base disorders: pH, pCO2, and HCO3−
- pH < 7.4 is acidosis
- pH > 7.4 is alkalosis
- Normal values for: Arterial blood pH (7.37-7.43) and venous blood (7.32-7.38)
Respiratory Regulation of pCO2
- Alveolar ventilation is regulated by pH.
- Increased [H+] increases alveolar ventilation.
- High alveolar ventilation lowers pCO2; low alveolar ventilation increases pCO2.
Renal Regulation of pCO2 and HCO3− Excretion
- Bicarbonate absorption, occurs in different sections of the renal tubules.
- The kidney regulates acid secretion and reabsorption to create a net acid excretion
- H+ and HCO3 - are regulated independently.
- Two major categories of noncarbonate bases (buffers): phosphate and ammonium
- Phosphate is relatively constant
- Ammonium is variable to accommodate varying acid excretion needs
Net Acid Excretion
- Net acid excretion is equal to the sum of NH4+ excretion and urinary titratable acid.
- Urinary titratable acid is measured by adding NaOH to the urine until pH becomes 7.4, determining how much acid is buffered.
Acid-Base Regulation by the Kidney
- The kidneys are responsible for maintaining acid-base balance by adjusting H+ and HCO3- in either the blood or urine.
Compensation (for Acid-Base Disorders)
- Respiratory and renal systems compensate for acid-base imbalances
- Respiratory compensation for metabolic disturbances occurs in ~30 minutes to 24 hours, and
- Renal compensation for respiratory disturbances takes ~3 to 5 days
Mixed Acid-Base Disorders
- These disorders involve two or more primary events acting together to cause disturbances in the acid-base system.
- Examples include respiratory acidosis with metabolic alkalosis.
Common causes of Acid-Base Disorders
- Respiratory acidosis results from decreased ventilation, causing increased CO2
- Respiratory alkalosis results from increased ventilation, causing decreased CO2
- Metabolic acidosis results from excessive acid production or insufficient bicarbonate to neutralize the acid
- Metabolic alkalosis results from excessive bicarbonate production or loss of acid
Potassium and Acid-Base Balance
- Potassium and acid-base imbalances are often noted together.
- Acid-base disorders can influence levels and distribution of potassium.
- Hypokalemia can increase H+ secretion and ammonia generation
- Hyperkalemia can impair NH4 production.
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Description
Test your understanding of the acid-base balance in the human body. This quiz covers essential concepts including pH levels, buffering systems, and the roles of respiratory and renal functions. Challenge yourself with questions related to the pH of various bodily fluids and the significance of different acid-base interactions.
