Renal Control of Sodium Ions Flashcards
Explain how changes in concentration of sodium affect blood pressure.
- Increase in concentration of sodium in the lumen of blood vessels results in a greater osmotic pressure
- Water moves to an area of higher osmotic pressure and therefore greater amount of water moves into the lumen of blood vessels
- This results in an increased extra cellular fluid
Which part of the nephron has the most variation in how much sodium is reabsorbed?
DCT
Which section of the nephron is a common target site of diuretics and why?
- DCT
- It is the most variation in how much sodium is reabsorbed
How does aldosterone increase reabsorption of sodium?
Increases production of eNac so more sodium is reabsorbed via the channel.
Define pressure natriuresis.
A central component of the feedback system for long-term control of arterial pressure is the pressure-natriuresis mechanism, whereby increases in renal perfusion pressure lead to decreases in sodium reabsorption and increases in sodium excretion
Define pressure diuresis.
Increased urinary excretion of water when there is an increase of arterial pressure, a compensatory mechanism to maintain blood pressure within the normal range.
TRUE OR FALSE:
Pressure natriuresis and diuresis always occur together.
True, because water follows sodium.
What ions does the Na-H antiporter (NHE) protein transporter move?
1 Na+ in, 1 H+ out
What ions does the Na-Glucose symporter (SGLUT) protein transporter move?
1 Na+ in, 1 Glucose in
What ions does the NaKCC2 protein transporter move?
1 Na+ in, 1 K+ in, 2 Cl- in
What ions does the NaCl co-transporter protein transporter move?
1 Na+ in, 1 Cl-
What ions does the ENaC protein transporter move?
1 Na+ in
What apical transporters are present on the PCT?
The PCT is split into 3 different segments which use different apical transporters for transcellular reabsorption.
These channels are required as the first segment is concerned with reabsorbing glucose, amino acids, HCO3- and Pi.
These channels are required as the second and third segment is concerned with reabsorbing chlorine and water.
How do the levels of PTH impact the NaPi channels present in the first segment of the PCT?
PTH also inhibits phosphate reabsorption in the kidney therefore decreases the presence of these channels.
Describe the function of the descending limb of the loop of Henle.
Site of water reaborption due to increased sodium in the interstitial fluid. Therefore water is passively reabsorbed forming an hypertonic environment within the tubule.
What is the tonicity of the tubule lumen like at the bottom of the loop of Henle?
Hypertonic
What is the tonicity of the tubule lumen like at the end of the thick ascending limb?
hypotonic
Describe the function of the thin ascending limb of the loop of Henle.
Basically the opposite of the descending limb. Here sodium is passively reabsorbed due to the low osmolality of the surrounding interstitial fluid.
Describe the function of the thick ascending limb of the loop of Henle.
This area of the loop of Henle is impermeable to water.
Here reabsorption of sodium becomes a more active process due to a lesser concentration gradient and also greater activity of 3Na-2K-ATPase. Therefore, the contents of the tubular lumen becomes increasingly hypotonic.
Name the main channel proteins present in the thick ascending limb.
3Na-2K-ATPase is present on the basolateral membrane in order to drive the movement of the apical channels which include, NKCC2, ROMK.
What ions does the ROMK protein transporter move?
One K+ out
What do loop diuretics inhibit?
Channel protein NKCC2
What do thiazide diuretics inhibit?
NaCl co-transporter channel protein
What do potassium sparing diuretics inhibit?
Channel protein ENaC
Describe the difference in channel proteins in the early and the late convoluted.
DCT 1: 3Na-2K-ATPase is present on the basolateral membrane in order to drive the movement of the apical channels which include, NaCl co-transporter.
DCT 2: 3Na-2K-ATPase is present on the basolateral membrane in order to drive the movement of the apical channels which include, NaCl co-transporter and ENaC.
What is the tonicity of the tubule lumen like at the end of the DCT and why?
Extremely hypotonic as the tubule is impermeable to water.
How is chloride reabsorbed in the DCT?
Both through NaCl co-transporter and paracellularly due to the electrochemical gradient formed by the movement of sodium ions through ENaC.
Which adrenal hormone increases the presence of ENaC within the DCT?
Aldosterone
Where is the major site of calcium reabsorbtion in the nephron?
DCT
What 2 hormones as the main regulators of Ca2+ reabsorbtion in the kidneys?
- PTH
2. 1,25-dihydroxyvitamin D (Calcitriol)
What 3 types of cells exist within the collecting duct of a nephron?
- Principal
- Acid intercalated (A-IC)
- Base intercalated (B-IC)
Describe the function of principal cells.
They reabsorb sodium through ENaC, this creates an electrochemical gradient which drives paracelluar reabsorption of chloride ions.
Also they are permeable to water so water reabsorption also occurs. (Depending on availability of aquaporrins)
Describe the function of intercalated cells.
To maintain acid base balance through excretion of H= ions and reabsorption of HCO3-.
