Renal Regulation

Question 1

the amount of K excreted in the feces is only about

Answer 1

5-10%

Question 2

increase in plasma potassium concentration of only _______ can cause cardiac arrhythmias,

Answer 2

3 to 4 mEq/L

Question 3

Insulin is important for increasing cell potassium uptake after a meal.
True or False

Answer 3

True

Question 4

Increases Potassium Uptake into Cells.

Answer 4

Insulin

Aldosterone

β-Adrenergic Stimulation

Question 5

treatment of hypertension with β-adrenergic receptor blockers, such as propranolol, causes

Answer 5

potassium to move out of the cells

Question 6

Renal potassium excretion is determined by the sum of three processes: (

Answer 6

1) the rate of potassium filtration (glomerular filtration rate [GFR] multiplied by the plasma potassium concentration)
2) the rate of potassium reabsorption by the tubules
3) the rate of potassium secretion by the tubules.

Question 7

normal rate of potassium f iltration by the glomerular capillaries is

Answer 7

756 mEq/day

Question 8

The most important sites for regulating potassium excretion are the

Answer 8

principal cells of the late distal tubules

and cortical collecting tubules.

Question 9

provides the driving force for passive diffusion of potassium from cell into the tubular lumen

Answer 9

high intracellular potassium concentration

Question 10

two types of special channels that allow potassium ions to rapidly diffuse across the membrane:

Answer 10

renal outer medullary potassium (ROMK) channels

high conductance “big” potassium (BK) channels

Question 11

primary factors that control potassium secretion by the principal cells of the late distal and cortical collecting tubules are

Answer 11

1) the activity of the sodiumpotassium ATPase pump
2) the electrochemical gradient for potassium secretion from the blood to the tubular lumen
3) the permeability of the luminal membrane for potassium.

Question 12

Increased Extracellular Fluid Potassium Concentration Stimulates Potassium reabsorption
True or False

Answer 12

False. K secretion

Question 13

Increased Extracellular Potassium Ion Concentration Stimulates Aldosterone Secretion
True or False

Answer 13

True

Question 14

The effect of decreased tubular flow rate is especially important in helping to preserve normal potassium excre-tion during changes in sodium intake.
True or False

Answer 14

False. Increased tubular flow rate

Question 15

Increased Distal Tubular Flow Rate Stimulates Potassium Secretion as occurs in

Answer 15

volume expansion,

high sodium intake, or treatment with some diuretics

Question 16

PTH regulates plasma calcium concentration through three main effects:

Answer 16

1) by stimulating bone resorption
2) by stimulating activation of vitamin D, which then increases intestinal reabsorption of calcium
3) by directly increasing renal tubular calcium reabsorption

Question 17

In the proximal tubule, calcium reabsorption usually parallels sodium and water reabsorption and is independent of PTH.
True or False

Answer 17

True

Question 18

PTH can play a significant role in regulating phosphate concentration through two effects:

Answer 18

1) PTH promotes bone resorption, thereby dumping large amounts of phosphate ions into the extracellular fluid from the bone salts
2) PTH decreases the transport maximum for phos-phate by the renal tubules, so a greater proportion of the tubular phosphate is lost in the urine.

Question 19

Regulation of magnesium excretion is achieved mainly by

Answer 19

changing tubular reabsorption.

Question 20

(1) increased extracellular fluid magnesium concentration
2) extracellular volume expansion, and
3) increased extracellular fluid calcium concentration.

Leads to

Answer 20

increased magnesium excretion:

Question 21

systemic adjustments

Answer 21

changes in blood pressure,
changes in circulating hormones, and
alterations of sympathetic nervous system activity.

Question 22

blood volume remains almost exactly constant despite extreme changes in daily fluid intake. The reason for this phenomenon is the following:

Answer 22

1) A slight change in blood volume causes a marked change in cardiac output
2) a slight change in cardiac output causes a large change in blood pressure
3) a slight change in blood pressure causes a large change in urine output.

Question 23

quantitative amounts of fluid distribution between the interstitium and the blood depend on

Answer 23

the physical properties of the circulation and

the interstitial spaces

as well as on the dynamics of fluid exchange through the capillary membranes.

Question 24

provides the basis for the chronic blood pressure–lowering effects of the angiotensin-converting enzyme inhibitors and Ang II receptor antagonists in hypertensive patients.

Answer 24

This shift of pressure natriure-sis

Question 25

most powerful sodium- and water-retaining hormones in the body

Answer 25

Ang II

Question 26

high levels of ADH do not cause major increases of either body fluid volume or arterial pressure, although

Answer 26

high ADH levels can cause severe reductions in extracellular sodium ion concentration.