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Regulation of Sodium and Water Excretion

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Which of the following cell types are not nerve cells?

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a. Pituitary cells that secrete ADH

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b. Baroreceptors located in pulmonary vessels

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c. Baroreceptors located in the arch of the aorta

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d. Intrarenal baroreceptors

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D. Intrarenal baroreceptors are modified smooth muscle cells in the afferent arteriole.

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In the production of aldosterone, the rate-limiting step is:

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a. the production of angiotensin I.

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b. the production of angiotensinogen.

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c. the activity of angiotensin-converting enzyme.

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d. the responsiveness of the adrenal gland to angiotensin II.

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A. The action of renin to produce angiotensin I is the rate-limiting step because (1) there is excess substrate (angiotensinogen) and (2) almost all angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE).

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A person eats a large bag of very salty potato chips with no beverage. Which response is most likely to ensue?

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a. Movement of aquaporins into the apical membrane of cortical collecting duct principal cells.

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b. Enhanced activity of Na-H antiporters in the proximal tubule.

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c. Enhanced activity of Na-K-ATPase pumps in collecting duct principal cells.

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d. Decreased levels of natriuretic peptides in the blood.

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A. Consumption of salt without water concentrates the ECF and triggers secretion of ADH. A key action of ADH is to cause insertion of aquaporins into the luminal membrane of cortical collecting duct principal cells.

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In response to a major hemorrhage:

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a. The afferent arteriole vasodilates.

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b. ADH secretion is reduced.

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c. Granular (juxtaglomerular) cells are stimulated by neural input.

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d. Neural baroreceptor firing rate increases.

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C. Loss of blood volume and likely ensuing drop of arterial pressure both reduce the inhibition of sympathetic outflow (i.e., sympathetic outflow increases). A prime target of sympathetic outflow in the kidneys is the juxtaglomerular cells.

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The macula densa generates signals that directly regulate

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a. smooth muscle in afferent arterioles.

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b. tubular water permeability....

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