Flashcards in Renal Test Deck (68):
Where is 98% of the Potassium in the body?
creates charge potential
What is normal Potassium concentration?
An increase in K+ ______ excitability.
Hyperkalemia _______ resting membrane potential, which ______ excitability.
What happens to Potassium immediately after ingestion in the GI tract?
Na/K ATPas rapidly takes up
What 3 hormonal factors are involved in the GI uptake of Potassium?
What role do kidneys play in regulation of body Potassium?
Excretion when K+ ECF too high
Where is filtered load of Potassium reabsorbed along the nephron?
90% Proximal tubule and Ascending limb
10% Delivered to distal nephron
How is Potassium excretion primarily regulated?
By controlling the rate of Secretion
*from capillaries into the collecting tubule
Potassium excretion primarily regulated by ______
Na and Water excretion primarily regulated by ________
How is it that a greater % of potassium is excreted than delivered to the distal nephron?
Secretion from Interstitium into late Distal Tubule and Collecting Tubule
What are 2 ways the Distal Nephron can compensate for Hypokalemia?
Where does Reabsorption occur in case of Hypokalemia?
Luminal: via K+/H+ antiporter
Basolateral: K+ selective
In normal Potassium Secretion/Reabsorption, what channels are crossed Luminally and Basolaterally
(1 luminal, 2 basolateral)
Luminal: Na/K ATPase
Basolateral: K+ channels and K+/Cl- cotransporters
How does an increase in Distal Na+ reabsorption affect Potassium secretion?
By creating Lumen Negative potential
(pushes K+ back into distal nephron)
A decrease in ECF H+ (alkalosis) will _____ plasma K+
An increase in ECF H+ (acidosis) will _______ plasma K+
*this occurs to maintain charge balance
Inorganic acids have a much greater effect on K+ than organic acids
Respiratory acidosis has little to no effect on Plasma K+
Does increase in ECF K+ concentration affect acid base status?
No?? It appears K is cleared in the kidneys through Secretion
What 2 things affect the rate of Potassium Secretion?
Tubular fluid flow rate
An increase in ECF (plasma) K+ concentration will increase Secretion/Excretion in what 2 ways?
Increases Na/K ATPase activity in Distal Nephrons
Increase Aldosterone secretion
*Ald has 2 effects
How does Aldosterone secretion increase K+ excretion (by secretion)?
Na/K ATPase activity
Luminal membrane permeability
In what 2 ways does an increase in tubular fluid flow increase K+ secretion?
Minimizes tubular fluid concentration
Increases Na+ reabsorption (which increases Na/K ATPase, increasing intracellular K+)
Extended use of loop diuretics leads to...
In what 2 ways does the use of loop diuretics increase K+ excretion?
(leading to hypokalemia)
Decreases K reabsorption in thick ascending limb
(by increasing tubular fluid flow and increasing distal Na absorption)
*and Na reabsorption drives K excretion by increasing Na/K ATPase and increases intracellular K
Why doesn't ADH increase K excretion even though it increases tubular fluid flow?
Resorbs water do distal nephron unaffected
Name 3 organs and 1 hormone that affect plasma Calcium levels.
Kidney, G-Intestinal, Bone
What are the 3 functions of the kidney in maintaining Calcium levels?
Vitamin D activation
Renal Calcium excretion/reabsorption (distal tubule)
Renal Orthophosphate excretion/reabsorption
What does PTH do to phosphate?
Decreases reabsorption (increasing excretion)
Inhibits Na/phosphate co-trnasporter on luminal membrane
How does PTH stimulate Calcium reabsorption in the Distal Tubule?
What is a volatile acid?
15-20,000 mmol/day CO2
Why are volatile acids usually of no concern?
What is a "Fixed" non-volatile acid?
2 things that create?
50 mmol/day inorganic/organic
Exercise, Diabetes (ketoacidosis)
Name 3 ways the body prevents major shifts in pH when there is constant generation of metabolic acids.
Renal compensation (H+ excretion, bicarb production)
What is the point of maximum buffering capacity?
Bicarb has dual control. The lungs regulate CO2. Kidneys regulate plasma concentration of bicarb.
What converts H2CO3 to water and carbon dioxide?
What is the typical value of plasma bicarb?
What is thy typical value of plasma CO2?
What ratio in the Henderson Hasselbach equation will result in a pH of 7.4?
The Henderson-Hasselbalch equation helps predict pH by evaluating what?
When CO2 diffuses into the RBC, it is converted to...
H+ and bicarb (HCO3-)
How does bicarb diffuse out of the lungs (after its trasformation from CO2)?
Exchanges with Cl-
The H+ left over in the RBC is buffered by de-oxygenated Hb.
H+ preferentially binds to de-oxygenated Hb
What 2 factors principally regulate respiration rate?
Plasma H+ concentration
What is the contribution of the Kidneys in the extreme case of HCl?
New bicarb generation
More than 99% of filtered bicarb is reabsorbed where?
The reabsorptive process of bicarb in the Proximal Tubule is _____
What is the mechanism of the Indirect bicarb reabsorption that occurs in the Proximal tubule
Carbonic Anhydrase forms bicarb Intracellularly, exports H+ to lumen, where bicarb + H+ > water and CO2
IC bicarb exits through basolateral membrane to ECF
*this is 1:1
What is the rate-limiting step in the reabsorption of bicarb in the Proximal tubule?
Where is bicarbonate generated in the nephron?
Distal Intercalated collecting tubule cells (titratable acids)
Proximal tubule (Glutamine metabolism)
Generation of new bicarb in distal collecting tubule from titratable acids is dependent on the availability of what?
*rate limiting step
What is metabolized in the proximal tubule to generate bicarb?
What is co-generated?
Why is it essential to have additional tubular buffers (like titratable acid and NH3) other than bicarb?
The source of renal NH3 is...
NH4 from Glutamine production
How can acid-base status affect NH3 synthesis?
Metabolic acidosis increases Glutamine metabolism
**increases bicarb synth
What are the 3 primary factors regulating H+ secretion?
Intracellular generation of H+
(water + CO2 via carbonic anhydrase = bicarb + H+)
(luminal, proximal tubule)
(luminal, intercalated collecting tubule)
Where does Aldosterone affect the regulation of bicarb?
Intercalated collecting tubule cells
How does Aldosterone affect the regulation of bicarb?
increases H+ ATPase
which increases H+ secretion
which increases HCO3 reabsorption
What are the 4 simple acid base disorders
How does the kidney compensate for Respiratory acidosis/alkalosis?
changes bicarb levels
A change in respiration rate can adjust CO2 levels in cases of Metabolic acidosis/alkalosis
The renal response for a change in pH due to Metabolic disturbances is what?
Resorb all filtered bicarb
Generate new bicarb
What is the proper acid base homeostatic level?
To compensate for metabolic acidosis, the kidney resorbs and synthesized new bicarb. If pCO2 is low so there's no H+ secretion, how does the body compensate?
What is an Anion Gap?
Means of identifying cause of metabolic acidosis