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32 Cards in this Set
- Front
- Back
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What structures are considered the "distal nephron"?
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Everything after the thick descending loop
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Describe the character of fluid entering the thin limb of loop of henle?
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Na same [] as plasma
Cl in higher [] as plasma due to HCO3 reabsorption in PCT NO glucose, AA, or protein Rich in K Rich in NH4+ because synthesized in PT |
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Is there much active transport activity in the thin limbs of henle?
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NAH BROnameth
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What are the functions of the descending and ascending loops of henle?
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Descending - permeable to water/impermeable to NaCl so allows water to be extracted from tubule as limb descends into hypertonic medulla
Ascending - impermeable to water/permeable to NaCl so NaCl diffused out of tubule |
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What is the net effect of the transport characteristics of the loop of henle?
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Reabsorb water and sodium isotonically
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What is the function of the thick ascending limb?
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Powerful NaCl transporter to dilute the urine
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What is the water permeability of the thick ascending limb?
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Impermeable
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What transporter is key to the thick ascending limb function?
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NKCC2
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What is the function of NKCC2?
Draw out the channel |
Transports 1Na, 2Ca, and 1 K from the lumen into the blood
see 385 for diagram |
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What is the NKCC2 driven by?
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Steep electrochemical gradient for Na established by the basolateral ATP Na pump
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A patient has a genetic defect in the K recirculating channel - ROMK. What would be the effect on urinary calcium excretion?
What can this cause? |
Increase excretion (in urine) - can cause Ca deposit in the kidney which can lead to scarring and fibrosis
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How are Ca and Mg transported out of the lumen in the TAL
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Lumen positive potential difference drive Ca/Mg out of the lumen PARACELLULARLY
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What 4 items are reabsorbed in the TAL?
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1. NaCl (25%)
2. Ca (20%) 3. Mg (70%) 4. NH3 (90%) |
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Describe the characteristics of the fluid entering the distal tubule?
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Hypotonic due to NaCl extraction in TAL
Dilution due to concomitant H2O impermeability Little K, NH4, HCO3 Some Ca, Mg, NaCl |
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What process starts to happen after the TAL?
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Fine tuning the urine
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The DCT is really made up of what?
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3 structures -
Early & Late DCT Connecting tubule |
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What are 3 important characteristics of the DCT?
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1. Steep chemical gradients
2. Hormonally regulated 3. Separate pathways for Na and other ion transport systems (altho sodium dependence often present) |
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Is NaCl reabsorped in the DCT?
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Some, but not much
NCCT transporter |
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What diuretic block NaCl reabsorption in the DCT?
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Thiazide
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Where are Mg and Ca reabsorbed in the DT?
How are they transported? |
Both are actively transported
Mg - in DCT1 and DCT2 Ca - In DCT2 and CNT |
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How is Mg transported into the DCT?
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Driven primarily by the luminal membrane potential established by voltage gated K+ channel
Magnesium pulled in through TRPM6 |
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How is Ca transported into the DCT?
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1. Enters via TRPV5 channel
2. Calbindin buffers Ca and it diffused to the basolateral membrane 3. Ca then extruded at the basolateral membrane by PMCA1b and NCX1 |
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Ca transport in the DCT is controlled by what?
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Calciotropic hormones such as PTH and Vitamin D
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What are the characteristics of the fluid leaving the DCT?
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Hypotonic
Less Na and Cl Little/no K Minimual Ca/Mg Acidic (little to no bicarb) |
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The collecting duct is the real site of what?
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Of action of K transport
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What characteristic of the CD favors K coming into the lumen?
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The negative potential
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What are the effects of Aldosterone on the collecting duct
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Increase the number/activiy of Na channel, ENaC, the Na-K pump, and K channels
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What are the 2 types of cells in the CD?
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PC
IC |
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IC cells do what?
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Can transport H+
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Draw out H+ excretion cycle in collecting duct
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see 404
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What is specifically transported in the collecting duct, especially if ADH is present?
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Urea
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Urea accumulates where as it is recycled?
What is the significance of this? |
Accumulates in the medulla
This drives water reabsorption |
