Glossary of Medullary concentration gradient
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- Why is it important to concentrate your urine?
How much can you conc. it?
- -To conserve body water.
-Conc up to 1200 mOsm, the same as the ISF of inner medulla.
- Where is ADH action important (in what renal cells)?
- In the collecting duct cells.
- How does ADH work?
- 1. It's carried in the blood.
2. Released, binds membrane receptor on coll. duct cell.
3. Activates cAMP-depend. PKA, which causes aquaporin II to
insert on lumenal membrane.
4. INCREASED H2O REABSORPTION.
- what is the min and max concentration that the filtrate can be?
- 50 Osm is minumum
1200 Osm is maximum.
- what is the purpose of countercurrent multiplication?
- to develop a concentrated ISF in the inner medulla, to allow H2o reabsorption from the medullary collecting duct.
- What ions move from which parts of the nephron, in order to develop the high ISF concentration?
- -Water reabsptn from desc limb.
-Na/Cl reabsptn from ascnd limb.
-Water NOT reabsbd from asc. lmb
- What is countercurrent exchange, and what is its purpose?
- -Exchange of H2O/Na/CL from peritubular capillaries. -Prevents washout of concentrated ISF develpd by countercurr. multiplication.
- What are the special peritub. capillaries called?
- Vasa recta, in inner medulla.
- How do H2O/Cl/Na move when flowing through vasa recta by the descending limb?
- H2O moves out, Cl/Na move in, so the blood is 1200 mOsm at the bottom of the loop.
- How do H2O/Cl/Na move when flowing through vasa recta by the ascending limb?
- H2O moves back in, Cl/Na move out, so the blood is once again 300 mOsm (normal) at the top.
- If there was no Vasa recta, what would happen?
- All of the Na/Cl creating the concentrated ISF would move down their gradient into blood vessels, and washout the ISF.
- what is urea's role in concentrating urine?
- As Na/Cl are reabsorbed from asc. limb, urea replaces them. This makes NaCl reabsptn more efficient. Urea is then reabsorbed at collecting duct.
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