Other #3

Question 1

What are the 4 causes of hypokalemia?

Answer 1

1. Vommitting
2. Diarrhea
3. Too much insulin
4. Alkalosis

Question 2

Where is phosphate mainly located?

Answer 2

85% of phosphate is located in our bone

Question 3

What are the 4 regulators of phosphate (P) metabolism?

Answer 3

1. Dietary- amount we ingest
2. Calcitroil–>reabsorbs phosphate from the bone and absorption from intestines
3. PTH–> reabsorbs phosphate from the bone and indirectly increses absorption from GI tract via calcitriol
4. Renal tubular reabsorption: PTH increases phosphate excretion by the kidneys (opposite of calcium). Thus, it can be reasorbed via the kidkneez

Question 4

What are the magnesium pools?

Answer 4

50% in bone

49% in ICF

1% in ECF

Question 5

We intake about 1500 mg phosphorus.

How much of that is reabsorbed?

Answer 5

About 900 mg.

Question 6

What would loss of potassium due to the volume of the cell?

Answer 6

The cell would shrink because it would also lose water.

Question 7

What maintains the “thirtyfold difference” in concentration between intracellular and extracellular potassium?

Answer 7

1. Na/K ATPase (expressed ubiquitously)
2. Na/K/2Ca channel
3. K-channels

Question 8

What would a significant decrease in potassium inside a cell do to the rate of protein synthesis?

Answer 8

It would decrease. Potassium is essential for protein synthesis

Question 9

What is the effect of a high plasma potassium concentration on vascular resistance?

Answer 9

High plasma potassium concentration results in vasodilation

Question 10

Why does alkalosis cause hypokalemia?

Answer 10

K+ is exchanged for H+ to try to bring our pH back down to normal

Question 11

How does hyperosmolarity affect K?

Answer 11

K+ will want to leave the cell because water goes from ICF–> ECF

Question 12

How is K+ reabsorbed in the PT?

Answer 12

K+ is reabsorbed via the creation of a + TEPD, allowing it to be reabsorbed paracellularu.

Question 13

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?

Answer 13

We want to increase the concentration of K (potassium) in the medulla.

1. K+ is secreted into the cortical CD.
2. K+ is then going to be reabsorbed in the medullary CD–> go into the interstitium
3. K+ will then be secreted in the late PT and the descending LOH, increasing K+ in the tubular fluid.
4. The increase of K+ in the tubular fluid will decrease NKCC2 reabsorption in the TAL.
5. 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.
6. Increases K+ secretion

Question 14

What part of the nephron is responsible for both secreting and reabsorping K+ to help fine tune our levels?

Answer 14

DT and cortical CD via principal cells and B intercalated cells.

Question 15

K+ is secreted in the late DT and CCD via principal cells and type B-intercalated cells. How is it secreted via principal cells?

Answer 15

Principle cell

Apical side: has ENac channels, BK and ROMKC channels.

BL side: Has Na/K ATPase

1. High plasma K+ will cause K to enter the cell via the NaKATPase
2. Na+ enters via the ENac
3. K+ leaves via the ROMKC and ENac

Question 16

Type B cells will also secrete K+

How?

Answer 16

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

Question 17

K+ reabsorption via intercalated A cells

Answer 17

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.

Question 18

What are the most important features that promote K+ secretion when it builds up in the ECF?

Answer 18

1. Increase in Na/K ATPases on the BL membrane
2. Increase in K+ leak channels on the apical membrane
3. Increase in distal tubule flow rate
4. Increased aldosterone
5. Decrease backflow of K+ from cell–> renal interstitium

Question 19

How does an increase in tubular flow rate increase K+ secretion

Answer 19

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.

Question 20

Decreased flow rate –>

Answer 20

K+ concentration build up early in the tubule–> decreasing concentration gradient between tubular fluid and cell (ECF and ICF)–> slows K+ secretion

Question 21

_____ is typically a problem with hypokalemia .

Answer 21

Alkalosis.

+ the activity of the Na/K ATPase pump.

Question 22

Acidosis –> ____ K+ secretion

Chronic acidosis–> ____ K+ secretion

Answer 22

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