DIT questions Flashcards
(104 cards)
What segment of the renal tubule reabsorbs 67% of the fluid and electrolytes filtered by the glomerulus?
Proximal tubule
What segment of the renal tubule is responsible for concentrating urine?
Collecting duct
What segment of the renal tubule is the site of secretion of organic anions and cations?
Proximal tubule
What segment of the renal tubule is always impermeable to water?
Thick ascending loop
What segment of the renal tubule is permeable to water in the presence of ADH
Late distal tubule and collecting duct
What segment of the renal tubule is the site of the Na/2Cl/K cotransporter?
Thick ascending limb
What segment of the renal tubule is the site of isotonic fluid reabsorption?
Proximal tubule
What segment of the renal tubule is responsible for diluting urine?
Thick ascending limb
What segment of the renal tubule is the only site where glucose and AA’s are reabsorbed?
Proximal tubule
What segment of the renal tubule that does water reabsorption in the Loop of Henle?
Thin descending limb
What 3 hormones or drugs act in the proximal tubule and what do they do?
Ang II -> stimulates apical Na+/H+ countertransporter -> puts H+ into the tubule (allows for HCO3 reabsorption via CA)
Carbonic anhydrase (CA) inhibitors: acetazolamide inhibits CA causing NaHCO3 diuresis and a metabolic acidosis
PTH: inhibits the apical Na+/phosphate cotransporter. Causes Phosphate excretion -> PTH = phosphate trashing hormone
What happens in the thin descending loop?
Concentration of urine due to passive water reabsorption while impermeable to Na+
What is important to know about the Thick ascending limb?
1) Na2ClK cotransporter
2) Impermeable to water (dilutes urine)
3) Leak back K+ channel creates + potential for paracellular reabsorption of Mg++ and Ca++
**Blocking the transporter with loop diuretics blocks the positive potential made by K+ back leak and therefore Ca++ will not get reabsorbed. LOOPS LOSE CALCIUM
What is important to know about the early distal tubule?
1) Na+/Cl- symporter
2) Impermeable to water (makes urine dilute)
3) Ca++ reabsorption controlled by PTH (stimulates the basolateral Na+/Ca++ exchanger -> pulls calcium into interstitium to create downward gradient for Ca++ to be pulled from lumen into tubule cell via Ca++ channel).
**LOOPS LOSE CALCIUM. THIAZIDES DONT
What determines how much water is reabsorbed in the distal tubules and collecting ducts?
ADH
What two types of intercalated cells?
H+ secreting and HCO3- secreting
What class of diuretics directly affects principle cells?
Potassium sparing diuretics: Aldosterone antagonists (spironolactone, eplerenone) and ENAC blockers (amiloride, triamterine)
What effect does aldosterone have on principle cells and intercalated cells of the collecting duct?
Principle cells- increases ENAC channels and stimulates the basolateral ATPase to cause Na+ reabsorption and K+ secretion.
Intercalated cells- stimulates H+ secretion
What drug antagonizes aldo’s action and promotes Na+ excretion and inhibits K+ excretion?
Spironolactone and eplerenone
What does ADH do besides other than its V1 and V2 receptor actions (vessel constriction and aquaporin insertion respectively)?
ADH also allows the very last portion of the medullary collecting duct to be permeable to urea. This allows for extreme hypertonicity of the interstitium and concentration of urine since water is also allowed to exit the distal tubule and collecting ducts to ADH.
What shifts potassium OUT of cells (causing hyperkalemia)?
INsulin puts K+ back INTO cells so....... DO low insulin LABB Digitalis hyperOsmolarity low insulin Lysis of cells Acidosis Beta Blockers
What shifts potassium into cells causing hypokalemia?
Insulin, hypo-osmolality, alkalosis, beta agonists, rapidly growing tumors
What are the normal ranges for pH, CO2, O2, and HCO3- in blood gas?
pH- 7.35-7.45
CO2- 35-45
O2- 75-105
HCO3- 22-28
How does acidosis/alkalosis affect extracellular K+ concentrations?
Acidosis -> incr H+/K+ pump -> hyperkalemia
Alkalosis -> pull K+ in and push H+ out -> hypokalemia