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Questions and Answers
What primarily determines the volume of blood plasma?
What effect does dehydration have on the body's water balance?
Which buffer system is the most important in plasma for maintaining acid-base homeostasis?
What component of the blood buffer system helps to eliminate H+ in the urine?
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How does the body typically respond to low osmolality?
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What is the primary function of chloride in the extracellular fluid?
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What is the average sodium content in the body of an adult?
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What happens to carbon atoms during the complete oxidation of fats, carbohydrates, and proteins?
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What is the principal cation in extracellular fluid?
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What percentage of the body water is classified as intracellular water?
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Which of the following best defines osmolality?
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What role do active transport mechanisms play in electrolyte distribution?
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Which ion is predominantly found in intracellular fluid?
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What is the primary means by which adults maintain water balance?
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How does osmotic pressure relate to water movement?
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Which of the following components is NOT considered an electrolyte in plasma?
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What is the primary function of the kidneys in acid-base balance?
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Which variable is crucial for calculating plasma pH using the Henderson-Hasselbach equation?
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How do the lungs contribute to acid-base homeostasis?
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What compensatory mechanism occurs during metabolic acidosis?
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What is meant by 'Base Excess' in blood acid-base homeostasis?
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What methods can be used to measure blood oxygen content?
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In metabolic alkalosis, what compensatory response occurs?
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How is CO2 content in plasma measured?
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Which component constitutes the major source of daily water loss?
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What is the volume of intracellular water in liters according to the distribution of body water?
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What is the normal range of arterial blood pCO2 for men?
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In which compartment is potassium (K+) concentration significantly higher?
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What is the effect on pH in metabolic acidosis?
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Which statement about the concentration of HCO3- in respiratory alkalosis is correct?
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Which ion has the highest concentration in extracellular fluid?
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What is the total daily water loss from all sites?
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What does oxygen saturation indicate?
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Which system is primarily responsible for excreting nonvolatile acids?
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Which compensation mechanism occurs in metabolic alkalosis?
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What constitutes the CO2 content in blood?
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Which of the following accurately describes the calculation of plasma pH?
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How does the organism primarily eliminate CO2?
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What effect does incomplete oxidation lead to in the body?
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What information is typically obtained from heart catheterization besides oxygen saturation?
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Study Notes
Electrolytes and Body Fluids
- Electrolytes are ions in plasma that greatly influence water balance and acid-base relationships.
- The internal environment refers to the concentration of ions and other substances in body fluids including H+ and pH.
- Homeostasis maintains a steady state with relatively constant concentrations of ions, pH, and osmotic pressure.
- Osmolality measures the number of dissolved particles per unit weight of water.
- Osmotic pressure is the hydrostatic pressure needed to prevent water from moving into a compartment of higher osmolality.
- Active transport moves ions or molecules across cell membranes against concentration gradients, requiring energy from ATP.
Body Water Composition
- Water makes up approximately 60% of total body weight.
- Intracellular water is found inside cells.
- Extracellular water is found outside cells.
- Plasma is the fluid in blood vessels.
- Interstitial fluid is the fluid between cells.
- Body water, with its dissolved salts and other substances, forms the internal environment.
Water Compartments
- 67% of body water is intracellular, while 33% is extracellular.
Water Balance
- An average adult consumes about 2500 ml of water daily through drinking and food intake.
- The same amount is lost daily through urine, feces, sweat, and expired air.
- Water balance is maintained by regulating fluid intake to compensate for daily losses.
Electrolyte Distribution
- Extracellular fluid is high in Na+ (over 90%), Cl-, and HCO3-.
- Intracellular fluid is high in K+ (77%) and phosphate.
- Active transport mechanisms maintain the differences in ionic concentration.
- The concentration of Na+ determines the osmotic pressure of extracellular fluids.
Plasma Volume
- Plasma is a subdivision of the extracellular fluid compartment.
- Its volume is determined by the concentration of Na+.
Correcting Disturbed Osmolality
- The body regulates water intake and excretion to maintain osmolality.
- Dehydration (high osmolality) stimulates thirst and ADH secretion, which leads to increased water reabsorption and reduced urine output.
- Overhydration (low osmolality) inhibits thirst and ADH secretion, resulting in increased urine output and dilute urine.
Sodium
- The average adult has about 80 g of sodium in their body.
- 35 g of sodium is in extracellular fluids.
- Sodium content remains relatively constant despite variations in intake.
Potassium
- Potassium is the dominant intracellular cation, with a concentration 30 times higher than in extracellular fluids.
- Dietary potassium salts are absorbed rapidly from the intestines but have minimal impact on plasma concentration.
Chloride
- Chloride is the dominant extracellular anion in serum.
- It plays a vital role in maintaining electrolyte balance, hydration, and osmotic pressure.
Acid-Base Homeostasis and Blood Buffer Systems
- Acid-base homeostasis maintains a stable pH in body fluids.
- Buffer systems are crucial for maintaining a stable pH.
- Major buffer systems include:
- Bicarbonate/Carbonic Acid Buffer System: The most important system in plasma, influenced by pulmonary ventilation.
- Hemoglobin Buffer System: Significant role in red blood cells.
- Phosphate Buffer System: Minor but important in urinary H+ elimination.
Blood Buffer Systems
- CO2 is produced during metabolism, forms H2CO3 in water, and is eliminated by the lungs.
- Incomplete metabolism produces nonvolatile acids, which the kidneys eliminate.
Effects of CO2, HCO3, and H2CO3 on pH
- Plasma pH depends on the ratio [HCO3]/[H2CO3].
- This ratio can be calculated using the Henderson-Hasselbalch equation.
Compensation of Acid-Base Disturbances
- Respiratory and renal systems compensate for blood pH disturbances.
- Metabolic acidosis is compensated by increased pulmonary ventilation and renal NH3 excretion.
- Metabolic alkalosis is compensated by renal HCO3 excretion and reduced respiration rate.
CO2 Content
- CO2 content includes dissolved CO2, undissociated H2CO3, and carbamino-bound CO2.
- Plasma or serum CO2 content is measured by automated colorimetric methods or ion-selective electrodes.
Blood Oxygen Content and Oxygen Saturation
- Blood oxygen content and saturation can be measured gasometrically, spectrophotometrically, or polarographically.
Blood Gases: pH, pCO2, and pO2
- The plasma CO2 content is closely related to plasma pH.
- The lungs are crucial for CO2 elimination.
Blood Oxygen Content and Oxygen Saturation
- Oxygen content and saturation are often determined during heart catheterization to locate catheter tip position.
Blood Buffer Systems
- The carbon atoms in fats, carbohydrates, and proteins are converted to CO2 during complete oxidation.
- CO2 is eliminated through respiration, while nonvolatile acids are excreted by the kidneys.
Effects of CO2, HCO3, and H2CO3 on pH
- CO2 is a product of oxidative metabolism and the source of plasma HCO3.
- Plasma pH is determined by the ratio of [HCO3]/[H2CO3].
Compensation of Acid-Base Disturbances
- Metabolic acidosis is compensated by increased pulmonary ventilation and renal NH3 excretion.
- Metabolic alkalosis is compensated by renal HCO3 excretion and reduced respiration rate.
CO2 Content
- CO2 content in plasma or serum is measured by automated methods or ion-selective electrodes.
Blood Oxygen Content and Oxygen Saturation
- Oxygen content and saturation are sometimes determined during heart catheterization.
Blood Gases: pH, pCO2, and pO2
- The lungs play a critical role in CO2 elimination.
Acid-Base Homeostasis and Blood Buffer Systems
- BB is the sum of buffer anions in whole blood.
- BE is the deviation of buffer base from normal.
- Oxygen tension (pO2) is the partial pressure of oxygen in blood.
- Oxygen content is the volume of oxygen bound to hemoglobin plus dissolved oxygen per 100 ml of whole blood.
- Oxygen saturation is the actual O2 content as a percentage of the fully oxygenated content of the blood.
Tables
- Table 3.1: Distribution of body water in adults, showing compartment percentages and volumes.
- Table 3.2: Daily water loss through various sites.
- Table 3.3: Concentration of cations and anions in extracellular and intracellular fluids.
- Table 3.4: Changes in acid-base parameters of whole arterial blood in acid-base imbalances.
- Table 3.5: Normal values of acid-base and blood gas constituents.
Figure 3.1:
- Diagram showing the transport of electrons and H+ in the respiratory chain in mitochondria, with reduced substrates being oxidized.
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Description
Test your knowledge on electrolytes, body fluids, and their roles in maintaining homeostasis. This quiz covers key concepts including osmolality, osmotic pressure, and the composition of body water. Understand how these factors influence your body's internal environment.
