Renal Regualtion Of Ion Concentrations

Question 1

Potassium EXCRETION is mostly involved where in the kidneys?

Answer 1

Mainly the Distal tubule and the Collecting Tubule

Question 2

What happens if the EC K+ levels increase by nearly double?

Answer 2

It can lead to Cardiac Arrhythmias

Question 3

What is the NORMAL IC [ ] of K+

Answer 3

140mEq/L

Question 4

EC K+ [ ]

Answer 4

4.2 mEq/L

Question 5

Total EC K+ in BODY compartments?

Answer 5

4.2 mEq/L x 14L

= 59 mEq

Question 6

Total IC K+ in BODY compartments?

Answer 6

140 mEq/L x 28L

= 3920 mEq

Question 7

Major factors responsible for K+ Excretion

Answer 7

• Direct influence on the Distal tubule and CD
  (Via Increase in EC [K+])
• Effect of ALDOSTERONE on K+ Excretion

Question 8

Increase in EC K+ leads to what?

Answer 8

The increase in ALDOSTERONE secretion

Question 9

Average intake of daily K+

Answer 9

100 mEq/day

A single meal can be as high as 50mEq

Question 10

Daily K+ output

Answer 10

100mEq/day total

• 92% ends up in URINE
• 8% ends up in FECES

Question 11

How many liters does the Kidney filter in one day?

Answer 11

180 Liters

Question 12

Potassium Reabsorption percentages in the tubules.

Answer 12

• 65% in the Proximal tubule
• 27% in the THICK Ascending limb
• 4% in the MEDULLARY CD

Total of -96%

Question 13

Potassium Secretion percentages in the tubules.

Answer 13

• 8% in the Distal Tubule/CORTICAL CD

- Total +8%

Question 14

Potassium Excreted percentages in the tubules.

Answer 14

100% - 96% + 8%

= 12% (92mEq/day)

Question 15

Small changes in K+ [ ] leads to what?

Answer 15

LARGE changes in ALDOSTERONE secretion by the Adrenals

Question 16

Direct and Indirect Influences on K+ Excretion

Answer 16

Direct
- High K+ [ ]

Indirect
- Aldosterone secretions

Question 17

Large amounts of K+ intake has what affect of the plasma K+ [ ]

Answer 17

Little changes

Question 18

Blockage of Aldosterone in the system leads to what?

Answer 18

Drastic accumulation of K+ in the body

Question 19

High potassium diet leads to what?

Answer 19

High Tubular flow rate

- to increase K+ Excretion

Question 20

Increase of Na+ intake on K+ Excretion

Answer 20

1. Increase in Na+ leads to an DEACREASE in Aldosterone secretion
   - This LOWERS K+ Excretion
2. Increase leads to an increase in GFR and decrease in prox tubule reabsorption of Na+
   - This RAISES K+ Excretion

‘K+ Excretion in UNCHANGED’

Question 21

PTH is most important in regulation of what?

Answer 21

Bone UPTAKE and RELEASE of Calcium

Question 22

Ca++ Acidosis

Answer 22

LESS Ca++ is bound to Plasma Proteins

Question 23

Ca++ Alkalosis

Answer 23

MORE Ca++ is Bound to the Plasma Proteins

Question 24

Parathyroid glands are Directly stimulated by what?

Answer 24

Low Ca++ levels

Question 25

A large amount of Ca++ excretion occurs where?

Answer 25

In Feces

Question 26

PTH Effects

Answer 26

• Stimulates bone Resorption
  (Release of Ca++ from Bone)
• Stim activation of Vit D
• INDIRECTLY Increases Tubular Ca++ Reabsorption

Question 27

Ca++ Reabsorption in the PROXIMAL Tubule

Answer 27

• 65% reabsorbed via the PARACELLULAR Route
• 20% reabsorbed via the TRANSCELLULAR Route

(99% of filtered Ca+ is reabsorbed)

Question 28

Ca++ is _____ and _____ in the kidneys, but it is NO ____?

Answer 28

Filtered and Reabsorbed

Secreted

Question 29

Ca++ reabsorption in the THICK Ascending Limb?

Answer 29

50% PC route
- Diffusion

50% TC route
- Stimulated by PTH

Question 30

Factors that Decrease Ca++ Excretion

Answer 30

1. Inc PTH
2. Inc Plasma [Po4]
3. Inc Metabolic ALKALOSIS

Question 31

Is Intestinal Ca++ reabsorption directly related to PTH

Answer 31

• No it is Indirectly

- Directly related to Inc in Vit D3

Question 32

Inc. in PTH has what effect on Phosphate?

Answer 32

Greater loss of Phosphate in the URINE

Question 33

T/F: Kidneys must be able to adjust K+ Excretion rapidly.

Answer 33

True

Question 34

What % of Total body K+ is in the ECF?

Answer 34

2%

Question 35

What Increases/Stimulates the uptake of K+

Answer 35

1. Insulin
2. Aldosterone
3. Catecholamines

Question 36

Effect of blood volume on increasing fluid intake?

Answer 36

No Effect