Reabsorption/Secretion in Proximal Tubule Flashcards
What fraction of the glomerular filtrate is reabsorbed?
2/3
Sodium is reabsorbed by an active transport mechanism?
True…this process is responsible for most of the energy consumption in the kidney
What is the significance of the electrochemical gradient created by pushing out 3 sodiums and letting in 2 potassiums with the Na/K ATPase pump?
By pushing out 3 positive charges and letting in 2, the pump creates a negative charge inside the cell that a positively charged sodium is highly attracted to. Thus, Na can passively diffuse into the cell and act as a carrier molecule by bringing other things with it,
What types of molecules are coupled with sodium?
bocarbonate, glucose, AA, organic acids
When sodium is reabsorbed, what comes with it?
Cl- so as to preserve electroneutrality
What drives water reabsorption>
The osmotic gradient created when solutes such as Na, Cl-, and HCO3 are reabsorbed. This creates higher osmolarity in the interstitial space and lower osmolarity in the tubule lumen, thus pulling water out of the lumen
What are the three peritubular factors that drive intake of fluid from the interstitial compartment to the capillary
1) positive interstitial fluid pressure 2) low hydrostatic pressure in peritubular capillary 3) High oncotic pressure in peritubular capillary
How is glucose reabsorbed?
Sodium glucose co-transporters (SGLT1 and SGLT2) . Completely reabsorbed until it reaches threshold
What is the Transport maximum?
All glucose transporters saturated
How to differentiate between threshold and transport maximum
Glucose will start appearing in the urine at threshold but reabsorption increases. At TM, no increase at all. How is this explained? ALl the nephrons are not the same, some nephrons get saturated quicker than others. At the TM,,,ALL are saturated.
