1b// Renal Regulation of Water and Acid-Base Balance Flashcards
How do you measure osmolarity and what are it’s units?
Concentration x number of dissociated particles
= Osm/ L or mOsm/ L
What is osmolality?
Osm/ Kg or mOsm/ kg
What is the osmolarity for 100mmol/ L of glucose and 100mmol/ L of NaCl?
glucose = 100mOsm/L
NaCl= 200mOsm/ L
What is osmotic pressure directly proportional to?
number of solute particles
What is a human’s body fluid distribution?
2/3 intracellular fluid
1/3 extracellular fluid
- of this 1/4 intravascular (plasma) and 3/4 extravascular
of the extravascular…
- 95% interstitial fluid
- 5% transcellular fluid
What separates intra and extracellular fluid?
cell membrane (phospholipid bilayer)
What separates extra and intravascular fluid?
capillary wall
Our total fluid volume is roughly how much of our body weight?
60%
What are examples of unregulated water loss? (4)
Sweat
Feces
Vomit
Water evaporation from respiratory lining and skin
What are regulated ways of water loss?
renal regulation (urine production- kidneys)
If you drink a lot of water does your urine become hyper or hypoosmotic?
Hypoosmotic
What happens to ECF, Na concentration and osmolarity when you drink lots of water?
increase ECF
decrease Na
Decrease in osmolarity
When you drink lots of water, do you require positive or negative water balance from renal regulation?
positive water balance
Describe positive and negative water balance.
*osmolarity normalises in the blood
*hyperosmotic urine is low in volume and dark in colour
How is water reabsorbed and what does it require?
passive process of osmosis and requries a gradient
Where is water reabsorbed in a nephron?
PCT
Descending limb of loop of Henle
Distal convoluted tubule
Collecting Duct
What does the loop of Henle and collecting duct require for water reabsorption?
The medullary interstitium needs to be hyperosmotic for water reabsorption to occur from the Loop of Henle and Collecting duct.
Where is most of the nephron and why?
in the cortex because there is more space
What 2 things happen in the loop of Henle?
Active salt reabsorption
Passive water reabsorption
How does active salt reabsorption and passive water reabsorption occur at the loop of Henle?
countercurrent multiplication (a continuous and dynamic process)
What is countercurrent Multiplication?
https://www.osmosis.org/learn/Kidney_countercurrent_multiplication
How does ICL describe countercurrent multiplication?
Water can be reabsorbed due to increased solute concentration within the juxtamedullary fluid. The ascending limb is effectively impermeable to water.
Tight junctions present in the ascending limb decrease paracellular transport of water.
Sodium chloride passively diffuses upon the hairpin bend, within the thin ascending limb.
Sodium chloride is actively transported out of the thick ascending limb.
N.B: Upon entering the descending limb of the loop of Henle, the filtrate is isotonic with the plasma.
Active salt reabsorption into the juxtamedullary interstitium by the thick ascending limb, reducing the water potential such that a gradient is established.
Passive water reabsorption through osmosis from the thin descending limb into
the hyperosmolar interstitium.
What would the 2 steps of countercurrent multiplication look like?
What is urea recycling according to osmosis?
Ut-A1
https://www.osmosis.org/learn/Urea_recycling
What is urea recycling according to ICL?
1) Urea enters the thin descending limb via UT-A2
2) At the collecting duct urea leaves via UT-A1 (apical cell membrane) then into interstitium via UT-A3 (basolateral cell membrane)
3) this increases interstitium osmolarity
4) Urine concentration occurs
5) then a small amount of urea from the interstitium enters the vasa recta via UT-B1
What increases UT-A1/3 numbers?
Vasopressin
- urea excretion requires less water
True or False.
NaCl and Urea are both responsible for generating hyperosmotic medullary interstitium.
True
True or False.
Intravenous fluid infusion first enters the intracellular fluid (ICF) and then travels to the ECF compartment.
False
True or False.
Osmolarity for 100mmol/ L NaCl is less than 200mmol/ L of Na+ ions.
False
What is the mechanism of action of ADH?
1) ADH binds to V2 receptors (basolateral side) on principal cells in the collecting duct
2) activates G protein on V2 receptor which activates adenylyl cyclase to turn ATP into cAMP
3) cAMP activates protein kinase A
4) protein kinase A triggering the translocation of aquaporins 2 from vesicles to the apical cell membrane
5) this causes more water to be reabsorbed into the cell via AQP2
6) water then leaves the cell on the basolateral side via AQP4 (and AQ3)
What happens at the thick ascending limb?
*Active Na Cl reabsorption
basolateral side:
1) NaK ATPase pump
- 2 K into cell
- 3 Na out of cell
2) KCl symporter
- 1 k and 1 Cl out of cell
3) facilitated diffusion of Cl via ion channels
apical side:
1) Na K 2Cl symporter
- 1 Na, 1 K, 2 Cl enter cell
2) facilitated diffusion of K out of cells via ion channels
What happens at the distal convoluted tubule?
*NaCl reabsorption
basolateral side:
1) Na K ATPase pump
- 2 K into cell
- 3 Na out of cell
2) K Cl symporter
- 1 k and 1Cl out of cell
3) facilitated diffusion of Cl via ion channels
apical side:
1) Na Cl symporter
What happens at the collecting duct?
*Principal Cell: Na+ reabsorption
basolateral side:
1) Na K ATPase pump
- 2 K into cell
- 3 Na out of cell
apical side:
1) facilitated diffusion of Na via ion channels into cell
What is the difference between diuresis and antidiuresis?
ADH amount is low during diuresis
- high during anti-diuresis
no aquaporins in distal convoluted tubule and collecting duct during diuresis
during anti-diuresis urine is roughly 1200 mOsm/ L (for diuresis it is roughly 50)
What is the cause, clinical features and treatment of AVP deficiency?
What is the cause, clinical features and treatment of SIADH?
What is the cause, clinical features and treatment of AVP resistance?
What are the equations for metabolic acid neutralisation?
Where does metabolic water go from these equations?
goes to the kidneys
What is the arrow equation for diet metabolism?
What is the ionic equation including bicarbonate ion and CO2?
What equation is used for measure pH?
In the nephron how much bicarbonate ion is reabsorbed and where?
What happens at the PCT?
basolateral side:
1) NaK ATPase pump on
2) Na HCO3 symporter side making them leave the cell
- called NBC1
- 1 Na and 3 HCO3
middle of the cell:
1) CO2 enters the cell via diffusion (lowkey basolateral side)
2) H + HCO –><– H20 + CO2
- via carbonic anhydrase
apical side:
1) Na H antiporter
- 1 H out of cell
- 1 Na into cell
- called NHE3
2) H ATPase pump
- called V-ATPase
- 1 H out of cell
outside of cell in tubular fluid:
1) H + HCO3 –> H2CO3 –> (CA) H2O + CO2
What happens at alpha intercalated cells of DCT and CD?
*HCO3- reabsorption and H+ secretion
basolateral side:
1) Cl HCO3 antiporter
- 1 Cl into cell
- 1 HCO3 out of cell
2) Cl facilitated diffusion via ion channel out of cell
inside cell;
1) H + HCO –><– H20 + CO2
- via carbonic anhydrase
apical side:
1) H ATPase pump
- called V-ATPase
- 1 H out of cell
2) H K ATPase
- 1 H out
- 1 K into cell
outside of cell:
1) H + HCO3 –> H2CO3 –> (CA) H2O + CO2
What happens at beta intercalated cells of the DCT and CD?
*HCO3- secretion and H reabsorption
basolateral side:
1) H ATPase pump
- called V-ATPase
2) facilitated diffusion of Cl via ion channel out of cell
inside cell:
1) H + HCO –><– H20 + CO2
- via carbonic anhydrase
apical side of cell:
1) Cl HCO3 antiporter
- 1 Cl into cell
- 1 HCO3 out of cell
What is the new bicarbonate ion production at the PCT?
Glutamine makes ammonium and A2-
The A2- makes bicarbonate which then enters the blood
ammonia leaves the cell via diffusion
ammonia also leaves via the NaH antiporter on the apical side
- NHE3
- 1 NH4 out and 1 Na in
antiporter NHE3 also makes H+ leave the cell
outside the cell…
H + NH3–> NH4
What is the new bicarbonate ion production at the DCT and CD?
outside of cell in tubular fluid
H + HPO4(2-) –> H2PO4-
