Renal Regualtion Of Ion Concentrations Flashcards
Potassium EXCRETION is mostly involved where in the kidneys?
Mainly the Distal tubule and the Collecting Tubule
What happens if the EC K+ levels increase by nearly double?
It can lead to Cardiac Arrhythmias
What is the NORMAL IC [ ] of K+
140mEq/L
EC K+ [ ]
4.2 mEq/L
Total EC K+ in BODY compartments?
4.2 mEq/L x 14L
= 59 mEq
Total IC K+ in BODY compartments?
140 mEq/L x 28L
= 3920 mEq
Major factors responsible for K+ Excretion
- Direct influence on the Distal tubule and CD
(Via Increase in EC [K+]) - Effect of ALDOSTERONE on K+ Excretion
Increase in EC K+ leads to what?
The increase in ALDOSTERONE secretion
Average intake of daily K+
100 mEq/day
A single meal can be as high as 50mEq
Daily K+ output
100mEq/day total
- 92% ends up in URINE
- 8% ends up in FECES
How many liters does the Kidney filter in one day?
180 Liters
Potassium Reabsorption percentages in the tubules.
- 65% in the Proximal tubule
- 27% in the THICK Ascending limb
- 4% in the MEDULLARY CD
Total of -96%
Potassium Secretion percentages in the tubules.
- 8% in the Distal Tubule/CORTICAL CD
- Total +8%
Potassium Excreted percentages in the tubules.
100% - 96% + 8%
= 12% (92mEq/day)
Small changes in K+ [ ] leads to what?
LARGE changes in ALDOSTERONE secretion by the Adrenals
Direct and Indirect Influences on K+ Excretion
Direct
- High K+ [ ]
Indirect
- Aldosterone secretions
Large amounts of K+ intake has what affect of the plasma K+ [ ]
Little changes
Blockage of Aldosterone in the system leads to what?
Drastic accumulation of K+ in the body
High potassium diet leads to what?
High Tubular flow rate
- to increase K+ Excretion
Increase of Na+ intake on K+ Excretion
- Increase in Na+ leads to an DEACREASE in Aldosterone secretion
- This LOWERS K+ Excretion - Increase leads to an increase in GFR and decrease in prox tubule reabsorption of Na+
- This RAISES K+ Excretion
‘K+ Excretion in UNCHANGED’
PTH is most important in regulation of what?
Bone UPTAKE and RELEASE of Calcium
Ca++ Acidosis
LESS Ca++ is bound to Plasma Proteins
Ca++ Alkalosis
MORE Ca++ is Bound to the Plasma Proteins
Parathyroid glands are Directly stimulated by what?
Low Ca++ levels
A large amount of Ca++ excretion occurs where?
In Feces
PTH Effects
- Stimulates bone Resorption
(Release of Ca++ from Bone) - Stim activation of Vit D
- INDIRECTLY Increases Tubular Ca++ Reabsorption
Ca++ Reabsorption in the PROXIMAL Tubule
- 65% reabsorbed via the PARACELLULAR Route
- 20% reabsorbed via the TRANSCELLULAR Route
(99% of filtered Ca+ is reabsorbed)
Ca++ is _____ and _____ in the kidneys, but it is NO ____?
Filtered and Reabsorbed
Secreted
Ca++ reabsorption in the THICK Ascending Limb?
50% PC route
- Diffusion
50% TC route
- Stimulated by PTH
Factors that Decrease Ca++ Excretion
- Inc PTH
- Inc Plasma [Po4]
- Inc Metabolic ALKALOSIS
Is Intestinal Ca++ reabsorption directly related to PTH
- No it is Indirectly
- Directly related to Inc in Vit D3
Inc. in PTH has what effect on Phosphate?
Greater loss of Phosphate in the URINE
T/F: Kidneys must be able to adjust K+ Excretion rapidly.
True
What % of Total body K+ is in the ECF?
2%
What Increases/Stimulates the uptake of K+
- Insulin
- Aldosterone
- Catecholamines
Effect of blood volume on increasing fluid intake?
No Effect
