Other #3 Flashcards
What are the 4 causes of hypokalemia?
- Vommitting
- Diarrhea
- Too much insulin
- Alkalosis
Where is phosphate mainly located?
85% of phosphate is located in our bone
What are the 4 regulators of phosphate (P) metabolism?
- Dietary- amount we ingest
- Calcitroil–>reabsorbs phosphate from the bone and absorption from intestines
- PTH–> reabsorbs phosphate from the bone and indirectly increses absorption from GI tract via calcitriol
- Renal tubular reabsorption: PTH increases phosphate excretion by the kidneys (opposite of calcium). Thus, it can be reasorbed via the kidkneez
What are the magnesium pools?
50% in bone
49% in ICF
1% in ECF
We intake about 1500 mg phosphorus.
How much of that is reabsorbed?
About 900 mg.
What would loss of potassium due to the volume of the cell?
The cell would shrink because it would also lose water.
What maintains the “thirtyfold difference” in concentration between intracellular and extracellular potassium?
- Na/K ATPase (expressed ubiquitously)
- Na/K/2Ca channel
- K-channels
What would a significant decrease in potassium inside a cell do to the rate of protein synthesis?
It would decrease. Potassium is essential for protein synthesis
What is the effect of a high plasma potassium concentration on vascular resistance?
High plasma potassium concentration results in vasodilation
Why does alkalosis cause hypokalemia?
K+ is exchanged for H+ to try to bring our pH back down to normal
How does hyperosmolarity affect K?
K+ will want to leave the cell because water goes from ICF–> ECF
How is K+ reabsorbed in the PT?
K+ is reabsorbed via the creation of a + TEPD, allowing it to be reabsorbed paracellularu.
In order for us to be able to secrete K+, the Na/K+ ATPase requires Na+ to be reabsorbed in the distal tubule.
How do we make sure enough Na+ arrives at the DT?
We want to increase the concentration of K (potassium) in the medulla.
- K+ is secreted into the cortical CD.
- K+ is then going to be reabsorbed in the medullary CD–> go into the interstitium
- K+ will then be secreted in the late PT and the descending LOH, increasing K+ in the tubular fluid.
- The increase of K+ in the tubular fluid will decrease NKCC2 reabsorption in the TAL.
- Allows more Na+ to remain in the lumen and go into the distal tubule, where it can be used to secrete more K+ into the tubular fluid.
- Increases K+ secretion
What part of the nephron is responsible for both secreting and reabsorping K+ to help fine tune our levels?
DT and cortical CD via principal cells and B intercalated cells.
K+ is secreted in the late DT and CCD via principal cells and type B-intercalated cells. How is it secreted via principal cells?
Principle cell
Apical side: has ENac channels, BK and ROMKC channels.
BL side: Has Na/K ATPase
- High plasma K+ will cause K to enter the cell via the NaKATPase
- Na+ enters via the ENac
- K+ leaves via the ROMKC and ENac
Type B cells will also secrete K+
How?
Apical side of the cell: HCO3-/H+ exchanger, K+ leak channels
BL: H/L ATPase
H+ concentration in the ISF is low.
Inside is the type B-intercalated cell, [CO2+H20–> HCO3- + H+], causing a build up of HCO3 and H+.
HCO3-/Cl- exchanger on the apical membrane secetes HCO3- into the urine and reabsorbs Cl-.
H/K ATPase on the BL membrane moves K+ into the cell and reabsorbed H+ into the ISF.
K+ is then secreted via K+leak channels
K+ reabsorption via intercalated A cells
Type A-intercalated cells are active under acidic conditions. They helps us secrete H+ ions and reabsorb HCO3.
Apical side: H/K+ ATPases, K+ leak channels
BL side: HCO3-/Cl exchanger
In the ISF, H+ concentrations are high.
[H+ + HCO3- → CO2]
[CO2 then moves inside the intercalated type-A cells]
Inside, we reconvert [CO2+ H20]–> [HCO3 and H+ ions]
H+ ions increase and are secreted via the H/K+ ATPases on the apical membrane which allow H+ to exit and K+ to be reabsorbed into the cell.
As K+ increases in the cell, it is reabsorbed into the ISF via K+ leak channels that are located on the apical membrane.
*HCO3- inside of the cell will be reabsorbed back into the ISF via HCO3-/Cl- exchanger.
What are the most important features that promote K+ secretion when it builds up in the ECF?
- Increase in Na/K ATPases on the BL membrane
- Increase in K+ leak channels on the apical membrane
- Increase in distal tubule flow rate
- Increased aldosterone
- Decrease backflow of K+ from cell–> renal interstitium
How does an increase in tubular flow rate increase K+ secretion
Increasing the distal tubule flow rate will dilute K+ in the tubular lumen, which will create a concentration gradient and promote K+ to be secreted.
Increased flow rate also increases Na+ delivered to the distal tubule for reabsorption–> Na+ reabsorbed via ENaC channels–> causing K+ to be secreted via the BK and ROMKC channels.
Decreased flow rate –>
K+ concentration build up early in the tubule–> decreasing concentration gradient between tubular fluid and cell (ECF and ICF)–> slows K+ secretion
_____ is typically a problem with hypokalemia .
Alkalosis.
+ the activity of the Na/K ATPase pump.
Acidosis –> ____ K+ secretion
Chronic acidosis–> ____ K+ secretion
Decrease
Stimulate; because our tubular flow rate will increase–> more Na+ is delivered to the distal tubule–> increase K+ secretion and also it will activate the RAAs system –> + K+ secretion
