Block 6 Renal Physiology Part 1

The best physiological buffering system in the plasma would be one that has a pK value closest to the physiological pH of around 7.4. Among the given weak acids, weak acid C has a pK value of 6.8, which is the closest to the physiological pH. Therefore, weak acid C would be the best physiological buffering system in the plasma.

The buffer that is most effective in the body is the one with a pK of 7.2. This is because the pH of the human body is around 7.4, which is slightly basic. A buffer with a pK close to the pH of the body will be able to resist changes in pH more effectively, as it will be able to accept or donate protons to maintain a stable pH. Therefore, a buffer with a pK of 7.2 would be the most effective in the body.

In congestive heart failure, the heart is unable to pump blood effectively, leading to decreased blood flow to the kidneys. This reduction in blood flow causes a decrease in the glomerular filtration rate (GFR), which is the rate at which the kidneys filter waste products from the blood. As a result, the plasma creatinine concentration increases because the kidneys are not able to effectively remove creatinine from the blood. This is why option a, a reduced GFR, is the correct answer.

A pH of 7.20 indicates acidemia (acidic blood). A PaCO2 of 73 mmHg indicates respiratory acidosis, which is caused by an increase in carbon dioxide levels in the blood. A plasma [HCO3-] of 28 mEq/L indicates compensated metabolic acidosis, which occurs as a compensatory mechanism to maintain pH balance. Therefore, the correct answer is acute respiratory acidosis.

The correct answer is d. Aldosterone-induced K+ secretion by principal cells. In patients with congestive heart failure, there is an activation of the renin-angiotensin-aldosterone system. Aldosterone acts on the principal cells of the collecting ducts in the kidneys, increasing the reabsorption of sodium and promoting the secretion of potassium. This leads to an increase in urinary potassium excretion and ultimately results in hypokalemia (low plasma [K+]).

The patient is experiencing metabolic acidosis as indicated by the low pH and low bicarbonate levels. The low bicarbonate levels suggest that there is an excess of acid in the body. The low PaCO2 levels indicate that there is some compensation by the respiratory system to try to increase the pH by blowing off more carbon dioxide. However, the compensation is not enough to bring the pH back to the normal range, indicating partial compensation. The other options are not supported by the given information.

Inhibition of carbonic anhydrase can lead to metabolic acidosis. Carbonic anhydrase is an enzyme that helps convert carbon dioxide and water into carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions. Inhibition of this enzyme disrupts the normal process of acid-base balance, leading to an accumulation of hydrogen ions and a decrease in bicarbonate ions. This imbalance results in metabolic acidosis, where there is an excess of acid in the body. The other options listed do not directly cause metabolic acidosis.

The correct answer is B, which corresponds to a pH of 7.55, a PaCO2 of 44 mmHg, and a plasma [HCO3-] of 40 mEq/L. This combination of values indicates a respiratory compensation for a primary metabolic alkalosis. The elevated pH and HCO3- levels suggest an excess of bicarbonate in the blood, which is characteristic of metabolic alkalosis. The slightly elevated PaCO2 indicates that the respiratory system is compensating by retaining carbon dioxide to try to normalize the pH.

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The central chemoreceptors require this time to adapt to the hypercapnia produced by attempts to hypoventilate. This means that it takes time for the chemoreceptors in the brain to adjust to the increased levels of carbon dioxide in the blood, which occurs when someone tries to decrease their breathing rate. Once the central chemoreceptors have adapted, they can effectively stimulate the respiratory system to increase ventilation and compensate for the metabolic alkalosis.

Prolonged diarrhea can lead to dehydration and loss of fluids, which can cause a decrease in blood volume. This decrease in blood volume stimulates the release of atrial natriuretic peptide (ANP) from the atria of the heart. ANP acts to increase the excretion of sodium and water by the kidneys, helping to restore fluid balance. Therefore, in this patient, it would be expected that the plasma concentration of ANP would be increased, not decreased.

In uncontrolled diabetes mellitus, the body is unable to properly regulate blood sugar levels, leading to hyperglycemia (high blood sugar levels). This can cause osmotic diuresis, where excess glucose in the urine pulls water out of the body, leading to dehydration. Positive glucose clearance refers to the body's attempt to remove excess glucose from the blood, which would be observed in uncontrolled diabetes. However, hypokalemia (low potassium levels) would not be observed in uncontrolled diabetes mellitus.

In congestive heart failure, the heart is unable to pump blood effectively, leading to a backup of blood in the systemic capillaries. This causes an increase in hydrostatic pressure, which forces fluid out of the capillaries and into the surrounding tissues, leading to edema. Renal failure, decreased ADH, increased plasma oncotic pressure, and increased urine output are not directly related to the development of edema in congestive heart failure.

Renal failure can lead to acidosis because the kidneys are responsible for maintaining the balance of acids and bases in the body. When the kidneys are not functioning properly, they are unable to excrete excess acid from the body, leading to an accumulation of acid in the blood. This can result in a decrease in blood pH, causing acidosis.

Increased formation of ammonia through glutamine is a compensation method for respiratory acidosis. In respiratory acidosis, there is an accumulation of carbon dioxide in the blood, leading to an increase in H+ ions and a decrease in pH. To compensate for this imbalance, the kidneys increase the production of ammonia through the metabolism of glutamine. Ammonia can then combine with H+ ions to form ammonium, which can be excreted in the urine, helping to restore the acid-base balance in the body.

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In diabetic ketoacidosis, there is an accumulation of ketones and acidic byproducts in the blood. To counteract the increased acidity, the body attempts to buffer the excess hydrogen ions (H+) by binding them to plasma proteins. This increased buffering of H+ by plasma proteins helps to maintain the pH balance in the blood. Hypoventilation (option a) is not typically observed in diabetic ketoacidosis. Increased utilization of glucose by skeletal muscle (option c) is not directly related to the acid-base balance. Decreased urinary phosphate buffering (option d) and decreased bicarbonate reabsorption (option e) would actually contribute to the acidosis rather than counteract it.

In nephritic syndrome, the glomerular basement membrane becomes more permeable, leading to increased filtration of protein. This results in a higher filtered load of protein and increased urine excretion. Glomerular filtration rate (GFR) may also be affected, as it is a measure of the rate at which fluid is filtered through the glomerulus. However, the transport maximum (Tm) for glucose transport in the proximal tubule is least affected because it is a separate process from the filtration of protein and does not depend on the integrity of the glomerular basement membrane. Therefore, the correct answer is d. Tm for glucose transport in the proximal tubule.

The given answer is E, which corresponds to a pH of 7.45, PaCO2 of 20 mmHg, and plasma [HCO3-] of 14 mEq/L. In respiratory alkalosis, the pH is elevated (>7.45) and the PaCO2 is decreased (

Metabolic acidosis is a condition characterized by an accumulation of acid or a loss of bicarbonate in the body, leading to a decrease in blood pH. In order to compensate for this acidosis, the kidneys increase the excretion of acid in the urine. This is done by increasing the production of ammonium ions (NH4+) and titratable acids, which help eliminate acid from the body. Additionally, the kidneys also conserve potassium in order to maintain electrolyte balance. Therefore, it would be expected that a patient with metabolic acidosis would exhibit an increase in urinary titratable acid and urinary ammonium concentration, as well as a decrease in urinary pH. However, urinary potassium excretion would not be increased in this condition.

In metabolic acidosis, the body tries to compensate by buffering excess H+ ions with intracellular proteins (option a), increasing the respiratory rate (hyperventilation) to remove CO2 (option c), and increasing the formation of ammonia and ammonium ions to excrete excess acid (option e). The movement of K+ from the interstitium into muscle cells (option b) is not a compensation mechanism for metabolic acidosis. Therefore, option b is the correct answer.

The patient with a pH of 7.32, [HCO3-] of 40, and PCO2 of 80 is the one who has suffered from pneumonia for several days. This is indicated by the lower pH, which suggests acidosis, and the higher PCO2, which indicates respiratory acidosis. Additionally, the [HCO3-] level is within the normal range, indicating compensation for the acidosis.

The given answer "D" is the correct answer because it indicates a pH value of 7.65, which is higher than the normal range of 7.35-7.45. This indicates alkalosis. Additionally, the PaCO2 value of 25 mmHg is lower than the normal range of 35-45 mmHg, indicating respiratory alkalosis. The plasma [HCO3-] value of 28 mEq/L is within the normal range of 22-28 mEq/L, indicating normal bicarbonate levels. Therefore, the combination of alkalosis and low PaCO2 suggests a mixed disturbance.

As blood flows through metabolizing tissues, carbonic acid is generated, which would normally decrease the pH. However, the pH decrease is less than expected because of the buffering effect of hemoglobin. Hemoglobin acts as a buffer by binding to hydrogen ions, preventing them from significantly affecting the pH. This buffering action helps to maintain a relatively stable pH in the blood despite the production of carbonic acid.

The given blood values indicate metabolic acidosis with a low bicarbonate level (HCO3-) and a low PaCO2. This suggests that there is an excessive loss of bicarbonate due to diarrhea. In response to dehydration, the body tries to maintain plasma volume by shifting fluid from the interstitial fluid (ISF) to the plasma. Therefore, the ISF volume decreases more than the plasma volume. This is supported by the fact that the chloride level (Cl-) is higher than normal, indicating a compensatory shift of chloride from the ISF to the plasma.

Ammonium enters the medullary interstitium by diffusion trapping.