Ren Reg Flashcards
Osmolarity equation
Concentration x no. of dissociated particles (Osm/L)
Body fluid distribution
2/3 intracellular fluid
1/3 extracellular fluid -1/4 intravascular (plasma) -3/4 extra vascular —95% interstitial fluid —5% transcellular fluid
Reabsorption thin descending limb
Water (passive) 15%
Reabsorption thick ascending limb
Sodium (active and passive)
Reabsorption of PCT
67% water
Reabsorption CD
Variable water
Urea recycling
Urea transported out of CD through UT-A1 (through apical cell membrane) and UT-A3 (through basolateral cell membrane) into medullary interstitium
Urea either goes to vasa recta (UT-B1) or loop of Henle (UT-A2)
Purpose of urea recycling
Increase osmolarity of interstitium
Urine concentration occurs
Urea excretion requires less water
Vasopressin production
Hypothalamus
Vasopressin storage
Posterior pituitary
Factors affecting ADH production
Plasma osmolarity - positive Blood pressure -negative Blood volume - negative Nausea - positive Angiotensin II - positive Nicotine - positive Ethanol - negative Atrial natriuretic peptide - negative
Mechanism of action for ADH
Bind to V2 receptor
Activates G protein signalling cascade
Activates adenylate cyclase and then protein kinase A
Increases secretion of aquaporin 2 channels in recycled form
Transported to apical cell membrane
Water flows through AQP 2 (apical cell membrane) and then AQP 3 and 4 (basolateral cell membrane) to be reabsorbed in blood
ADH effect on aquaporin
AQP2 and 3 affected as required based on water intake
Diuresis thick ascending limb
Increased dilute urine excretion
Sodium reabsorption
(3)Sodium (2)potassium ATPase pump, potassium chlorine symporter and chlorine channel out to create low sodium concentration within
Sodium potassium (2)chlorine symporter pump in down gradient
Diuresis collecting duct
Sodium passive in
(3)Sodium (2)potassium ATPase out
Antidiuresis effect
Thick ascending limb: Sodium potassium chlorine (2) symporter increase
DCT: Sodium chlorine symporter increase
Collecting duct: Sodium channel increase
Role of kidney in acid base balance
Secretion and excretion of H+
Reabsorption of HCO3-
Production of new HCO3-
Reabsorption of bicarbonate ion percentage
PCT - 80%
Ascending limb - 10%
DCT - 6%
Collecting duct - 4%
Fluid leaving PCT into thin descending limb
Isoosmotic
Fluid leaving thick ascending limb into DCT
Hypoosmotic
Fluid leaving DCT into CD
Hypoosmotic
Diuresis DCT
Sodium potassium ATPase pump and potassium chlorine symporter out
Sodium chlorine symporter in
Reabsorption of bicarbonate in PCT
CO2 enter cell by diffusion from tubular fluid
With water through carbonic anhydrase, produce H+ and bicarbonate
H+ leaves to tubular fluid through sodium hydrogen antiporter or hydrogen ATPase
Bicarbonate is reabsorbed into blood through sodium bicarbonate symporter
Reabsorption of bicarbonate in DCT and CD
Alpha intercalated cell (normal)
- proton ATPase pump or proton potassium ATPase pump H+ into tubular fluid
- chlorine bicarbonate antiporter pump bicarbonate into blood
Beta intercalated cell (acidosis)
- chlorine bicarbonate antiporter pump bicarbonate into tubular fluid
- proton ATPase pump H+ into blood
Production of new bicarbonate in PCT
Glutamine gives two molecules of ammonium and glutamate, which turns to 2 bicarbonates and reabsorbed
Ammonium exit through tubular fluid through sodium proton antiporter (substitute proton) or becomes ammonia and binds with proton in tubular fluid to become ammonium
Production of new bicarbonate in DCT and CD
Alpha intercalated cell
- hydrogen enters tubular fluid and neutralised by phosphate buffer system
- gains one bicarbonate ion
Metabolic acidosis characteristic
Decreased bicarbonate
Decreased pH
Metabolic acidosis compensation
Increased ventilation
Increases bicarbonate reabsorption and production
Metabolic alkalosis characteristic
Increased bicarbonate
Increased pH
Metabolic alkalosis compensation
Decreased ventilation
Increased bicarbonate excretion
Respiratory acidosis characteristic
Increased PCO2
Decreased pH
Respiratory acidosis compensation
Acute - intracellular buffer
Chronic - increases bicarbonate reabsorption and production
Respiratory characteristic
Decreased PCO2
Increased pH
Respiratory alkalosis compensation
Acute - intracellular buffer
Chronic - decreased bicarbonate reabsorption and production
