Renal Regulation Flashcards
the amount of K excreted in the feces is only about
5-10%
increase in plasma potassium concentration of only _______ can cause cardiac arrhythmias,
3 to 4 mEq/L
Insulin is important for increasing cell potassium uptake after a meal.
True or False
True
Increases Potassium Uptake into Cells.
Insulin
Aldosterone
β-Adrenergic Stimulation
treatment of hypertension with β-adrenergic receptor blockers, such as propranolol, causes
potassium to move out of the cells
Renal potassium excretion is determined by the sum of three processes: (
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.
normal rate of potassium f iltration by the glomerular capillaries is
756 mEq/day
The most important sites for regulating potassium excretion are the
principal cells of the late distal tubules
and cortical collecting tubules.
provides the driving force for passive diffusion of potassium from cell into the tubular lumen
high intracellular potassium concentration
two types of special channels that allow potassium ions to rapidly diffuse across the membrane:
renal outer medullary potassium (ROMK) channels
high conductance “big” potassium (BK) channels
primary factors that control potassium secretion by the principal cells of the late distal and cortical collecting tubules are
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.
Increased Extracellular Fluid Potassium Concentration Stimulates Potassium reabsorption
True or False
False. K secretion
Increased Extracellular Potassium Ion Concentration Stimulates Aldosterone Secretion
True or False
True
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
False. Increased tubular flow rate
Increased Distal Tubular Flow Rate Stimulates Potassium Secretion as occurs in
volume expansion,
high sodium intake, or treatment with some diuretics
PTH regulates plasma calcium concentration through three main effects:
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
In the proximal tubule, calcium reabsorption usually parallels sodium and water reabsorption and is independent of PTH.
True or False
True
PTH can play a significant role in regulating phosphate concentration through two effects:
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.
Regulation of magnesium excretion is achieved mainly by
changing tubular reabsorption.
(1) increased extracellular fluid magnesium concentration
2) extracellular volume expansion, and
3) increased extracellular fluid calcium concentration.
Leads to
increased magnesium excretion:
systemic adjustments
changes in blood pressure,
changes in circulating hormones, and
alterations of sympathetic nervous system activity.
blood volume remains almost exactly constant despite extreme changes in daily fluid intake. The reason for this phenomenon is the following:
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.
quantitative amounts of fluid distribution between the interstitium and the blood depend on
the physical properties of the circulation and
the interstitial spaces
as well as on the dynamics of fluid exchange through the capillary membranes.
provides the basis for the chronic blood pressure–lowering effects of the angiotensin-converting enzyme inhibitors and Ang II receptor antagonists in hypertensive patients.
This shift of pressure natriure-sis
most powerful sodium- and water-retaining hormones in the body
Ang II
high levels of ADH do not cause major increases of either body fluid volume or arterial pressure, although
high ADH levels can cause severe reductions in extracellular sodium ion concentration.
