Regulation of Sodium and Water Excretion
Which of the following cell types are not nerve cells?
a. Pituitary cells that secrete ADH
b. Baroreceptors located in pulmonary vessels
c. Baroreceptors located in the arch of the aorta
d. Intrarenal baroreceptors
(d) Intrarenal baroreceptors are modified smooth muscle cells in the afferent arteriole.
In the production of aldosterone, the rate-limiting step is
a. the production of angiotensin I.
b. the production of angiotensinogen.
c. the activity of angiotensin converting enzyme.
d. the responsiveness of the adrenal gland to angiotensin II.
(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 angiontensin converting enzyme (ACE).
A person eats a large bag of very salty potato chips with no beverage. Which response is most likely to ensue?
a. Movement of aquaporins into the membranes of cortical collecting duct principal cells.
b. Enhanced activity of Na–H antiporters in the proximal tubule.
c. Enhanced activity of Na-K-ATPase pumps in collecting duct principal cells.
d. Decreased levels of natriuretic peptides in the blood.
(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.
In response to a major hemorrhage
b. ADH secretion is reduced.
c. Granular (juxtaglomerular) cells are stimulated by neural input.
d. Neural baroreceptor firing rate increases.
(c) Loss of blood volume and likely ensuing drop of arterial pressure both reduce the inhibition of sympathetic outflow (ie, sympathetic outflow increases). A prime target of sympathetic outflow in the kidneys is the juxtaglomerular cells.
The macula densa generates signals that directly regulate
b. Sympathetic neural activity.