Question 1

Which of the following best describes the concept of Effective Circulating Blood Volume (ECBV)?

Accepted Answer

The portion of blood volume that is actively perfusing tissues and contributing to blood pressure.

Question 2

A patient has an extracellular fluid sodium content of 1700 mEq and a plasma sodium concentration of 140 mEq/L. What is the extracellular fluid volume ($$ECF_{volume}) in $$liters? Use the formula $$ECF_{volume} = \frac{ECF\ Na\ (mmoles)}{P_{Na}}.$$

Accepted Answer

$$12.1\ L$$

Question 3

Which of the following is TRUE regarding the regulation of sodium balance compared to water balance?

Accepted Answer

Water balance is achieved more rapidly than sodium balance.

Question 4

Which physiological parameter is most directly determined by the total body sodium content?

Accepted Answer

Extracellular fluid volume

Question 5

A patient with volume depletion (hypovolemia) is likely to have which of the following changes in extracellular fluid sodium and volume?

Accepted Answer

Decreased ECF sodium and decreased ECF volume

Question 6

Which of the following mechanisms is NOT a direct sensor of changes in effective circulating blood volume?

Accepted Answer

Renal tubular cells sensing sodium concentration

Question 7

Which segment of the nephron is primarily responsible for the bulk reabsorption of sodium?

Accepted Answer

Proximal tubule

Question 8

Which hormone increases sodium reabsorption in the distal nephron and collecting duct?

Accepted Answer

Aldosterone

Question 9

Which of the following is NOT an action of angiotensin II?

Accepted Answer

Inhibition of ADH release

Question 10

A patient is given a drug that blocks the action of aldosterone. What is the expected effect on sodium excretion?

Accepted Answer

Increased sodium excretion

Question 11

Which of the following is a primary effect of atrial natriuretic peptide (ANP)?

Accepted Answer

Decrease tubular sodium reabsorption

Question 12

Which of the following would most likely result in a drop in effective circulating blood volume (ECBV)?

Accepted Answer

Acute hemorrhage

Question 13

Which of the following equations correctly relates extracellular fluid volume ($$ECF_{volume}$$), sodium quantity, and plasma sodium concentration?

Accepted Answer

$$ECF_{volume} = \frac{ECF\ Na\ (mmoles)}{P_{Na}}$$

Question 14

Which of the following is a direct effect of sympathetic nerve activity on sodium handling by the nephron?

Accepted Answer

Increased sodium reabsorption in the proximal tubule and thick ascending limb

Question 15

A patient with heart failure has elevated levels of atrial natriuretic peptide (ANP). What is the expected effect on renal sodium excretion?

Accepted Answer

Increased sodium excretion

Question 16

Which of the following would most likely trigger the release of renin from the juxtaglomerular apparatus?

Accepted Answer

Decreased effective circulating blood volume

Question 17

Which of the following is a consequence of volume expansion (hypervolemia) due to increased sodium intake?

Accepted Answer

Increased extracellular fluid volume

Question 18

Which of the following is NOT a function of angiotensin II in the regulation of sodium balance?

Accepted Answer

Stimulating atrial natriuretic peptide release

Question 19

A patient with low effective circulating blood volume is likely to have which of the following compensatory responses?

Accepted Answer

Increased aldosterone secretion

Question 20

Which of the following best explains why the renal system cannot directly sense changes in extracellular fluid volume?

Accepted Answer

The renal system relies on pressure sensors in the vasculature to detect changes in blood volume.

Regulation of Sodium Balance: Mechanisms and Physiological Significance

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