Renal Test Flashcards
Where is 98% of the Potassium in the body?
Why?
Intracellular
creates charge potential
What is normal Potassium concentration?
4 mEq/L
An increase in K+ ______ excitability.
Increases
Hyperkalemia _______ resting membrane potential, which ______ excitability.
Decreases
Increases
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?
Epinepherine
Insulin
Aldosterone
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 ________
Secretion
Reabsorption
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?
Secretion stops
Reabsorption
Where does Reabsorption occur in case of Hypokalemia?
Luminal/Basolateral channels?
Distal nephron
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?
How?
Increases
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+
Decrease
Increase
*this occurs to maintain charge balance
T/F
Inorganic acids have a much greater effect on K+ than organic acids
True
T/F
Respiratory acidosis has little to no effect on Plasma K+
True
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?
Plasma potassium
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)?
2 things
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…
Hypokalemia
In what 2 ways does the use of loop diuretics increase K+ excretion?
(leading to hypokalemia)
Decreases K reabsorption in thick ascending limb
Increases secretion
(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
PTH
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
(HPO4 -2)
What does PTH do to phosphate?
Where?
Mechanism?
Decreases reabsorption (increasing excretion)
Proximal Tubule
Inhibits Na/phosphate co-trnasporter on luminal membrane
How does PTH stimulate Calcium reabsorption in the Distal Tubule?
2 things
Ca ATPase
Na/Ca exchanger
basolateral membrane
What is a volatile acid?
15-20,000 mmol/day CO2
*oxidative metabolism
Why are volatile acids usually of no concern?
Exhaled
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.
Bicarb
CO2 respiration
Renal compensation (H+ excretion, bicarb production)
What is the point of maximum buffering capacity?
pKa
T/F
Bicarb has dual control. The lungs regulate CO2. Kidneys regulate plasma concentration of bicarb.
True
What converts H2CO3 to water and carbon dioxide?
Carbonic Anhydrase
What is the typical value of plasma bicarb?
24 mmol/L
What is thy typical value of plasma CO2?
1.2 mmol/L
What ratio in the Henderson Hasselbach equation will result in a pH of 7.4?
20:1
The Henderson-Hasselbalch equation helps predict pH by evaluating what?
Acid/Base ratio
CO2/bicarb
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-
T/F
The H+ left over in the RBC is buffered by de-oxygenated Hb.
True
T/F
H+ preferentially binds to de-oxygenated Hb
True
What 2 factors principally regulate respiration rate?
CO2 levels
Plasma H+ concentration
What is the contribution of the Kidneys in the extreme case of HCl?
2 things
New bicarb generation
H+ excretion
More than 99% of filtered bicarb is reabsorbed where?
Proximal tubule
The reabsorptive process of bicarb in the Proximal Tubule is _____
Indirect
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?
H+ ATPase
Where is bicarbonate generated in the nephron?
2 places/processes
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?
Urinary buffers
*rate limiting step
What is metabolized in the proximal tubule to generate bicarb?
What is co-generated?
Glutamine
Ammonium
Why is it essential to have additional tubular buffers (like titratable acid and NH3) other than bicarb?
Quick depletion
The source of renal NH3 is…
NH4 from Glutamine production
How can acid-base status affect NH3 synthesis?
Metabolic acidosis increases Glutamine metabolism
Increases NH4
increases NH3+
**increases bicarb synth
What are the 3 primary factors regulating H+ secretion?
Intracellular generation of H+
(water + CO2 via carbonic anhydrase = bicarb + H+)
H/Na antiporter
(luminal, proximal tubule)
H+ ATPase
(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
Metabolic/Respiratory Acidosis/Alkalosis
How does the kidney compensate for Respiratory acidosis/alkalosis?
changes bicarb levels
*slow response
T/F
A change in respiration rate can adjust CO2 levels in cases of Metabolic acidosis/alkalosis
True
The renal response for a change in pH due to Metabolic disturbances is what?
2 things
Resorb all filtered bicarb
Generate new bicarb
What is the proper acid base homeostatic level?
7.4
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?
Hypoventilation
What is an Anion Gap?
Means of identifying cause of metabolic acidosis
If acidosis is from an organic acid, there is a _____ in gap,
If acidosis is from an inorganic acid, there is _____ in gap
Change
No change
