Lecture 3 Flashcards
Closest to Glomerulus?
Proximal Tubule
Na+ reabsorption is quantitatively greatest in?
Proximal Tubule (~67%)
Reabsorption of most other solutes (and isosmotic reabsorption of water) is?
Quantitatively greatest in PCT
Isoosmotic Reabsorption?
No change in Osmolarity
TF/plasma?
Concentration in tubule compared to plasma
Increase K+?
ICF
Increase Na+?
ECF
Na+ Dependent Cotransporters?
-Glucose
-HPO4-/SO4-
-Amino Acids
Glucose?
(GLUT2)
Passive transport with carrier protein
Glucose (SGLT1)?
Driven by Na+ gradient
Na+ (SGLT1)?
Active process dependent on Na+
(Reabsorption of Glucose)
Filtered?
Increase glucose in plasma = Increase filtration rate
(Reabsorption of Glucose)
Excreted Equation?
Excreted = Filtered - Reabsorbed
Sodium pumps operate on?
Side facing capillaries
Na goes in with?
Cotransporter into cell on Lumen Side
Cotransporter uses Na gradient as a?
Driving force (it is active because generated by sodium pump)
Cotransporter uses Na gradient as a?
Driving force (it is active because generated by sodium pump)
Glucose enters lumen side into cell via?
SGLT1
GLUT2?
Like a carrier, glucose goes down chemical gradient
Curve 1 (Filtered)?
Amount of glucose being filtered for kidney
Curve 3 (Reabsorbed)?
Behaves very similar to group being filtered, then it has a plateau
(NaCl Reabsorption in late PCT)
Na+ reabsorption in late PCT occurs?
Mostly with Cl-
(NaCl Reabsorption in late PCT)
Both Na+ and Cl- cross?
PCT by transcellular (2/3) and paracellular (1/3) pathways
(Osmotic Water Reabsorption in PCT)
Water is passively reabsorbed via?
Transcellular and Paracellular Pathways due to Osmotic gradient established by transport of NaCl
Proximal Tubule Summary?
-2/3 of salts and water reabsorbed
-All glucose and amino acids reabsorbed
-Reabsorption is isotonic (PT Osmolality is isotonic at beginning and end)
Na+ Transport Along Nephron?
-Na+ reabsorption is quantitatively greatest in proximal tubule
-Reabsorption of most other solutes (and isosmotic reabsorption of water) is also quantitatively greatest in PCT
Which portion has NO Na+ reabsorption?
Thin descending limb and Thin ascending limb
Thin descending limb of loop of Henle?
-Low permeability to solutes
-High permeability to water
Thin Descending Limb of Loop of Henle increases in osmolarity because?
H2O leaves
Thick Ascending Limb of Loop of Henle (TAL)?
Diluting segment
-Impermeable to H2O
-Special carriers co-transport ions from tubule to interstitium
Counter Current Multiplier creates?
Osmolarity gradient
Counter Current Multiplier?
-Increases interstitial osmolarity
-Decreases tubular osmolarity
Blood moving through kidney removes a lot of?
Osmolites
Counter Current Exchange dependent on?
Osmolarity
Counter Current Exchange is a function of?
Vasa Recta Capillaries
(to provide nutrients and oxygen to deep kidney while maintaining gradient)
Distal Convoluted Tubule has?
Decrease Osmolarity
Principal Cells in Cortical Collecting Duct?
Absorb Na+ and secrete K+
Intercalated Cells in Cortical Collecting Duct?
Secrete acid/base equivalents and can also reabsorb K+
Collecting Duct is the site of?
ADH (principal cells) action
Collecting Duct is divided into 2 segments?
-Cortical Collecting Duct
-Medullary Collecting Duct
ADH increases?
Tubular Permeability to Water
Binding of ADH to basolateral membrane of principal cells results in?
Insertion of water channels (Aquaporin-2) into apical membrane
In absence of ADH, channels are?
Recycled and apical membrane is again impermeable to water
In absence of ADH, channels are?
Recycled and apical membrane is again impermeable to water
Variable Permeability to H2O is regulated by?
Antidiuretic Hormone (ADH)
(concentrate urine)
Summary of ADH Actions on Kidneys?
1) Increases permeability of entire collecting duct to water
2) Increases permeability of medullary collecting duct to urea
3) Decreases vasa recta blood flow
4) Increases expression of Na/K/2Cl transporter in thick ascending limb (TAL)