[6] Loop of Henle and Distal Convoluted Tube Flashcards
What occurs in the descending loop?
Descending: Dry
Water diffuses out
What occurs int he thick ascending loop?
Ascending: Asin
Na+ diffuses down electrical gradient
Osmolarity at the top of nephron
Osmolarity at the bottom of nephron
300 milliosmoles
1200 milliosmoles
Why does the interstitium have to be concentrated?
Otherwise you’ll urinate to death
Main Function: Countercurrent Multiplier
Create a hyperosmotic medullary interstitium
Have an osmotic equilibrium of water in the medulllary collecting tubules and medullary interstitium
[Red Slide]
What clinical conditions will produce a concentrated urine?
A dilute output?
Do research, send me answers. =))
[Descending Limb of Henle]
What is it permeable to?
What is it impermeable to?
P: Water
I: Na and Cl
[Descending Limb of Henle]
How does water pass?
Aquaporin 1
[Thin Ascending Limb of Henle]
What is it permeable to?
What is it impermeable to?
Highly impermeable to water
Permeable to Na, Cl and Urea
What’ll happen to Potassium levels if the Na K 2Cl pump gets deactivated?
Research
[Red Slide]
What happens if a drug inhibits the area of the thick ascending limb of the Loop of Henle?
Research
[Major Problem of the Loop of Henle]
How does NaCl get out of the thin ascending loop?
Urea concentration gradient helps move sodium out of the loop
[Red Slide]
What happens in persons with Marasmus in terms of the concentration gradient
They are frequently urinating because they have no urea. Since they have Marasmus, which has a lack of protein, and urea is a byproduct of protein breakdown, they cannot create a very concentrated urine.
Kidney receives what % of CO?
20%
How many liters/day of glomerular filtrate?
180 liters
What keeps NaCl from leaving the medulla?
Vasa Recta
Origin of the Vasa Recta
Efferent Arterioles
[Red Slide]
How does Mannitol, an osmotic diuretic, increase urine output?
Increases renal blood flow in the vasa recta, allowing less time to concentrate your urine.
Active pumping out of NaCl occurs where?
Thick Ascending Loop
CCD: Principal Cells
Effect of Aldosterone and Vasopressin
Opens water and sodium channels
Ammonia Secretion
Glutamine -> NH3 + H -> NH4 + Cl -> NH4Cl
Where is Glutamine secreted?
Proximal Tubule
OMCD has which Aquaporins?
2 and 3
IMCD mainly Water Absorption/Secretion?
What about Urea?
Absorption for both
Intercalated cells increase/decrease in number as collecting duct descends?
Decrease
Is the collecting duct permeable/impermeable to water?
Impermeable
Function: Macula Densa
Na-K-Cl Reabsorption
Adenosine Secretion
Function: DCT1
Na and MG Reabsorption
Function: DCT2
H and K Secretion
CA Reabsorption
Function: CNT
Na, K, Ca reabsorption
K Secretion
Function: CCD
H AND HCO3 SECRETION
Water and Na Reabsorption
Function: OMCD
H and NH3 Secretion
Water Reabsorption
Function: IMCD
Water and UREA Reabsorption
Gitelman Syndrome
NCCT
Classic Bartter Variant
Cl-CK2b
Clinical Presentation of Patient with Gitelman Syndrome
Hyponatremia because there is a lot of salt loss
Primarily hypovolemic then dehydration because of the salt loss
Do you treat a dehydrated person immediately?
What about a hypovolemic person?
Slowly to get the system accustomed to it
Immediately
What electrolyte problems do you foresee in patients with Gitelman Syndrome?
Research
What electrolyte problems do you foresee in patients with AE1 Mutations?
Research
AE1: Cl-HCO3 Antiport
AE1: Distal Renal Tubular Acidosis
Hyperchloremic metabolic acidosis
Type 1 Pseudohypoaldosteronism (PHA)
Liddle Syndrome
What symptoms do you expect in patients with Liddle Syndrome?
WNK1
4-Type II PHA
Nephrogenic Diabetes Insipidus
AQP2- Autosomal Nephrogenic Diabetes Insipidus
What electrolyte problems do you foresee in patients with AQP2 defects?
Hypernatremia due to the closed aquaporins that are a result from the lack of ADH
What does Thiazide block?
Na-Cl Symporter
What do Lactones Block?
Aldosterone Receptors
[Red Slide]
How do thiazides prevent kidney stone formation?
Research
[Red Slide]
How do K-sparing diuretics help in patients with Gitelman syndrome?
Research
Memorize that Chart with Values of Substances Related to Loop Areas
Go look for it =))
Potassium is primarily taken up by the
A. H-K ATPase
B. K-Cl Co-Transporter
C. Na-K-ATPase Pump
D. ROMK Channels
Don’t know yet, wanna tell me?
What is the major intracellular ion?
Potassium
How does K exit cells?
Mostly via K Channels
Some via K-H Exchange
Majority of Potassium is found in?
Muscles
Least Potassium found in which organs?
Plasma
Which of the following conditions causes more hypokalemia?
A. Anuria
B. Polyuria
C. Constipation
D. Diarrhea
B
Because more potassium is excreted via urine
Majority of K is excreted via?
Urine 90meq/day
Feces 10meq/day
Aldosterone affects which pumps?
Na-K Pump
Changes in K concentration have marked effects on?
Cell Excitability
Potassium is a major intracellular?
Osmotically Active Cation
Potassium is critical for what activities?
Enzyme
Cell Division
Growth
Intracellular K participates in?
Acid Base regulation
Which phase of the propagation of the action potential permits potassium ions to exit the cell?
A. Resting Potential
B. Action Potential
C. Repolarization
D. Hyperpolarization
C
Action Potential
Na moves inside the membrane
Repolarization
K move outside and sodium stays inside the cell
Hyperpolarization
More K on the outside than Na on the inside
Refractory
K returns inside
Na returns outside
Buffering of ECF K through cell K uptake is impaired in the absence of?
Aldosterone
Insulin
Catecholamines
Characteristics: Renal Outer Medulla K, SK/ROMK
Low Conductance
pH Sensitive
Characteristics: Ca++-Acitvated (BK/Maxi-K)
High Conductance
Flow Stimulated
Characteristics: H-HK ATPase
Colonic: Resorption
Gastric: Secretion
Majority of K Secretion Occurs in:
A. PCT
B. TAL
C. DCT
D. CD
Don’t know, wanna tell me?
Fate of Potassium
65% in PCT: Passive Diffusion
25% in TAL: Na-K-2Cl Pump
3% DCT
10% OMCD
1% IMCD
Secretion of Potassium
10-50% DCT
5-30% CCD
15-80% IMCD
What factors are needed to facilitate renal K secretion
A. ANP
B. Distal delivery of NA
C. ECFV Contraction
D. All of the Above
TIP: Usually not All of the Above for Dr. Anacleto
Don’t know, wanna tell me?
What is the most important regulation for management of potassium problems?
Dietary K
What happens in Hyperkalemia
Stimulates secretion of K via principal cells in DT/CCD
High K Intake
Stimulates Aldosterone and SK/ROMK, BK/maxi-K channels
Low K Intake
Enhance colonic H-K-ATPase
Effect on Exercise on K Levels
Release of K from muscles
Opening of K channels
What counterbalances the increase of K from exercise?
Catecholamines which decrease extracellular K
Luminal Flow Rate
High Flow Rate -> High K Secretion in DT/CCD
If you urinate too much what kind of potassium problems will you have?
If you don’t urinate at all what kind of potassium problems will you have?
Hypokalemia
Hyperkalemia
Alkalosis leads to?
Acidosis leads to?
Alk: Hypokalemic, increased K secretion
Aci: Hyperkalemic, decreased K secretion
Effect of Acidosis on Na pump
Lowers cellular potassium levels
Effect: Increased luminal bicarbonate levels?
Increased potassium secretion