Renal - Pt 4 Reabsorption/Secretion/Hormones Flashcards
[] % of reabsorption occurs in the TAL.
25%
There are no [] reabsorption in the TAL due to true tight junctions.
Paracellular
TAL Reabsorption: Apical Membrane
- [] (NKCC) symporters present in the apical membrane. This transporter brings the 3 ions [] the cell.
- [] leak channels allow K+ to leak out of the cell.
- Na+/K+/2 CL- (NKCC) symporters present in the apical membrane. This transporter brings the 3 ions into the cell.
- Potassium leak channels allow K+ to leak out of the cell.
- Resorption in the TAL differs from the PCT in that water [] follow the electrolytes as they are reabsorbed.
- The TAL of the loop of Henle is always [] to water.
- cannot
- impermeable
- [] inhibits the NKCC transport in the TAL
- This causes urine output to dramatically []
- Urine sodium amounts []
- However the body tries to [] Na+ past hthe TAL
- Plasma Potassium Amounts drastically []
- Furosemide inhibits the NKCC transport in the TAL
- This causes urine output to dramatically increase
- Urine sodium amounts increase
- However the body tries to reabsorb Na+ past the TAL
- Plasma Potassium Amounts drastically decrease
TAL Reabsorption: Basolateral Side
- [] and [] leak channels allow the ions to to be reabsorbed through the basolateral membrane
- Na+/K+ pumps move Sodium acorss the basolateral membrane for [].
- Cl- and K+ leak channels allow the ions to to be reabsorbed through the basolateral membrane
- Na+/K+ pumps move Sodium acorss the basolateral membrane for resorption.
T/F
Active transport moves Na+ into the interstitial fluid of th descending limb of the loop of Henle.
False
There is not active transport in the descending limb of the loop of Henle.
- In the descending loop of Henle, [] transport of solutes does not readily occur and there is limited [] to sodium and chloride ions.
- However, [] is freely permeable to move via osmosis to the [] fluid.
- In the descending loop of Henle, active transport of solutes does not readily occur and there is limited permeability to sodium and chloride ions.
- However, water is freely permeable to move via osmosis to the interstitial fluid.
The medullary gradient is formed by the [] cotransporters in the [].
The medullary gradient is formed by the NKCC cotransporters in the TAL.
The osmolarity of fluids in the interstitial space of the cortex is approximately [] mOsm/L, while the osmolarity within the medulla can climb up to values of approx [] mOsm/L.
300 mOsm/L
1200 mOsm/L
- The loop of Henle is associated with the Counter-current [] system
- The vasa recta participate in a diffusion process called the counter current [] system.
- Multiplier
- Exchange
T/F
No reabsorption happens in the DCT.
False
Roughly 5% of solutes still need to be reabsorbed around the DCT…but most solutes are absorbed in the PCT and TAL
- The [] is the main site of hormone reabsorption regulation
- The 2 hormones involved are [] and []
- DCT
- Aldosterone and ADH (anti-diuretic Hormone)
- Aldosterone controls [] reabsorption
- ADH controls [] reabsorption
- Sodium
- water
- The largest percentage of secretion occurs in the [] and [] []
- This is because [] junctions are not true tight junctions in the [], but they are in the DCT. So, when something is [] in the DCT, it stays secreted and cannot leak back into the interstitial fluid.
- The largest percentage of secretion occurs in the DCT and collecting duct
- This is because tight junctions are not true tight junctions in the PCT, but they are in the DCT. So, when something is secreted in the DCT, it stays secreted and cannot leak back into the interstitial fluid.
Most of the secretion that occurs in the DCT and Collecting Duct is by [] transport via [] carriers.
active
protein
Potassium is secreted in the [] DCT and collecting duct via a sodium/potassium ATPase embedded in the [] membrane, and a [] [] channel in the [] membrane.
Potassium is secreted in the late DCT and collecting duct via a sodium/potassium ATPase embedded in the basolateral membrane, and a K+ leak channel in the apical membrane.
- Water is [] by the hormone ADH (also called []) from the [] [] gland.
- ADH leads to the insertion of proteins called [] into the mebranes of the late DCT and Colecting Ducts…allowing for the [] of water.
- Water is saved by the hormone ADH (also called vasopressin) from the posterior pituitary gland.
- ADH leads to the insertion of proteins called aquaporins into the mebranes of the late DCT and Colecting Ducts…allowing for the reabsorption of water.
- Sodium is saved by the hormone [] from the adrenal glands.
- This hormone [] the number and activity of sodium/potassium pumps in the tubule allowing for an increase in sodium []and potassium [].
- Sodium is saved by the hormone aldosterone from the adrenal glands.
- This hormone increases the number and activity of sodium/potassium pumps in the tubule allowing for an increase in sodium reabsorption and potassium secretion.
The release of ADH is controlled by cells in the hypothalamus called [].
Osmoreceptors
Osmoreceptors and ADH
- Osmoreceptors are receptive to their own cell []
- If the oncentrationf of extracellular fluid becomes high (like during []) –> the cell []—> increass rate of action potentials –> [] release of ADH
- Osmoreceptors are receptive to their own cell size
- If the concentration of extracellular fluid becomes high (like during dehydration) –> the cell shrinks —> increases rate of action potentials –> increases release of ADH
An [] in the stretch of baroreceptors will lead to a [] secretion of ADH
An increase in the stretch of baroreceptors will lead to a decrease secretion of ADH
What 2 mechanisms did we learn of that can effect the release of ADH from the posterior pituitary?
Osmoreceptors - stimulation causes increased ADH
Baroreceptors - stimulation causes decreased ADH
If both the baroreceptors and osmoreceptors are signaling the posterior pituitary for ADH, the [] will have a greater effect.
Osmoreceptors
- ADH travels through the bloodstream and binds to [] receptors in the late DCT and CD.
- This stimulates the insertion of [] channels into the apical membrane and allows for [] of water.
- ADH travels through the bloodstream and binds to V2 receptors in the late DCT and CD.
- This stimulates the insertion of aquaporin-2 channels into the apical membrane and allows for reabsorption of water.
Other effects of ADH:
- Stimulates []
- Increases activity of the[] symporter in the [] [] limb of hte loop of Henle
- Increaes nephron permeability to [] in the medullary [] [].
- Stimulates thirst
- Increases activity of the NKCC symporter in the thick ascending limb of hte loop of Henle
- Increases nephron permeability to urea in the medullary collecting duct.
ADH also leads to the insertion of urea transporters, called [] in the medullary [] [].
ADH also leads to the insertion of urea transporters, called ureaporins in the medullary collecting duct.
Production of Hypo-Osmotic Urine:
- Drink H2O —> decrease plasma osmolarity —> [] osmoreceptor firing —> [] ADH release —> decrease H2O reabsorption in Late DCT and Collecting Duct —> [] urine osmolarity & [] urine volume —> [] plasma osmolarity
Drink H2O —> decrease plasma osmolarity —> decrease osmoreceptor firing —> decrease ADH release —> decrease H2O reabsorption in Late DCT and Collecting Duct —> decrease urine osmolarity & increase urine volume —> increase plasma osmolarity
Production of Hyper-Osmotic Urine
- Deprived of H2O —> increase plasma osmolarity —> [] osmoreceptor firing —> []ADH release —> increase H2O reabsorption in Late DCT and Collecting Duct —> [] urine osmolarity & [] urine volume —> [] plasma osmolarity
Deprived of H2O —> increase plasma osmolarity —> increase osmoreceptor firing —> increase ADH release —> increase H2O reabsorption in Late DCT and Collecting Duct —> increase urine osmolarity & decrease urine volume —> decrease plasma osmolarity
