Renal Transport Cont. Flashcards
(43 cards)
Factors that stimulate Na+ Reabsorption?
- Na + deficiency
- Hyponatremia
Factors that stimulate Na+ Secretion?
- Hypernatremia
- Prostaglandins
- ANP
If there is a problem with Na+ concentration, the problem is usually involved with?
Water
Factors that stimulate K+ Secretion?
- K+ Excess
- Aldosterone
Factors that stimulate K+ Reabsorption?
- K + deficiency
- Hypokalemia
What 2 things cause ADH to be released?
- Hyperosmolarity
2. Volume Depletion
ADH is more sensitive to small changes in?
Osmolality!
What are the 3 mechanisms of ADH?
- Increase water permeability
- Increase Urea permeability
- Increase activity of NKCC2
Where does ADH increase water permeability?
Principal cells in the distal tubule
How does ADH increase water permeability at principal cells in the distal tubule?
Inserts AQPs into apical membrane
Which AQP does ADH insert on to the apical membrane of principal cells in the distal tubule?
AQP - 2
Since ADH can insert AQP - 2 on to principal cells, what will this cause?
Water will be REABSORBED
Under the action of ADH, water is reabsorbed. What is left behind in the tubule?
UREA
Where in the nephron is the [urea] really HIGH?
Inner Medullary Collecting Duct
What happens when the [urea] is really high in the inner medullary collecting duct?
It will diffuse out passively
Describe how Urea is recycled under the actions of ADH
ADH causes more water to be reabsorbed at the distal tubule
- This leaves Urea behind in the distal tubule with concentrations increasing
- Once at the inner medullary collecting duct, urea will passively diffuse out of the tubule
- Urea will then eventually diffuse back into the tubule upstream
ADH also increases the activity of the NKCC2 at the thick ascending limb. What does this cause?
More reabsorption of Na, K, 2Cl. Further, due to back leak of K+ this indirectly causes more reabsorption of Mg and Ca!
Where is the Kidney Interstitium and what does it contain?
Between tubules and vessels
- contains Interstitial fluid, ECM and cells
As you move from the Kidney’s cortex, to outer medulla, to inner medulla, what increases?
Interstitium Osmolality!
The kidney interstitium osmolality increases as you move towards?
Inner medulla
What 2 mechanisms control urine concentration?
- Counter Current Multiplier
2. Counter Current Exchanger
With the Counter Current Multiplier, what leaves the Ascending limb and enters the kidney interstitium?
NaCl
With the Counter Current Multiplier, as NaCl enters the interstitium, what does this cause to happen to the interstitium?
It becomes hyperosmotic
With the Counter Current Multiplier, as NaCl enters the interstitium, what will leave the Descending limb?
Water
