Kidney lecture 2: Regulation of water and salts

What are the 2 mechanisms of which Na+ moves from tubules into cells during reabsorption

Co-transport with other molecules e.g glucose

Counter-transport of hydrogen ions (Na+ in, H+ out)

How is Na+ moved from cells to interstital space and then blood via active transport during reabsorption?

Via Na+/K+ ATPase pump which requires ATP and K+ then returns to interstitial fluid via ion channels down a conc gradient

Overall diagram of Na+ reabsorption in the proximal tubule

How is Na+ moved from tubules into cells via cotransport with K+ and Cl- in the ascending loop of henle?

Via Na-K-Cl cotransporter (NKCC) where K+ moves back into tubule via ion channels down a concentration gradient

How are Na+ ions moved out to interstital space and K+ ions into cells in the ascending loop of henle?

Na+/K+ ATPase moves Na+ out to interstitial space and K+ into cells of which K+ returns to interstitial fluid via ion channels down the conc gradient

Overall diagram of the process of Na+ reabsorption in the ascending loop of henle

Overall process of Na+ reabsorption in the collecting duct

Tube - Cell: Na+ moves into cell and K+ moves out through ion channel, down a concentration gradient.

Cell - Body: Na+/K+ ATPase moves Na+ out to interstitial space and K+ into cells

Hormonal control in the collecting duct and Aldosterone

Process takes hours so effect of aldosterone also takes time to be released into the body and have an impact

Water reabsorption descending loop of henle

How does the counter current mechanism help with water reabsorption in the loop of henle?

Having a longer loop of henle allows you to…

Reabsorb more water

Water reasborption in the collecting ducts

Hormonal control during water reabsorption in the collecting duct