Renal Regulation Of Water And Acid-Base Balance Flashcards
What is the body fluid distribution?
1/3 = extracellular fluid (ecf)
1/4 of this is intravascular and 3/4 is extravascular
2/3 intracellular fluid
What do positive and negative water balances cause in ECF, NA+ and Osmolarity
How much water is reabsorbed in each part of a nephron and where?
Why does a gradient need to be kept during this process and what functions are in place to do this?
What osmotic state does the interstitium need to be in to allow osmosis?
2/3 in pct
15% in thin descending limb loop of henle
Osmosis is a passive process so it requires a constant gradient, we use countercurrent multiplication and urea recycling
Interstitium needs to be in a hyperosmotic state
Explain countercurrent multiplication and why it’s important for water absorption
In the thick ascending limb of the nephron, there is active salt réabsorption of nacl to create a concentration gradient between the loop of henle and the interstitium. This allows for water to continuously be reabsorbed as there is a continuous osmotic gradient. This continues happening time and time again
What is urea recycling?
In the collecting duct, there are 2 transporters ut-1 (apical) and ut-3 (basal) which pick up urea from the collecting duct to the interstitial space to increase its osmolality.
This creases a conc gradient which increases the amount of water reabsorbed
How does HCO3- act as a buffer?
What actions does the kidney have in acid/base balance?
Binds to free H+ ions to form H2CO3- which can dissociate into H20 and new HC03-
To keep our acid levels down
It secretes h+, Reabsorb hco3-, Produce new hco3-
What inhibits and stimulates ADH production?
What is its mechanism?
Stimulate: increased plasma osmolarity, decreased blood pressure, angiotensin II, nicotine
Inhibit: decrease plasma osmolarity, hypervolemia, increased blood pressure, ethanol, ANC (atrial natriuretic peptide)
Mechanism:up/downgrades AQP2 and AQP3 numbers
How do you calculate osmolarity? Osm/L or moms/L
Concentration x no. Of dissociated particles
How is NaCl reabsorbed in the thick ascending loop of henle
How is NaCl reabsorbed in the distal convoluted tubule
How is Na+ reabsorbed in the collecting duct
NaKCl symporter moves ions into the renal tubular epithelial cell from the lumen, then Na/K/ATPase moves it into the blood
Na+Cl symporter followed by Na/K+/ATPase into the blood
Diffuses itself into the cell and then enters blood via Na/K+/ATPase
What is the treatment for NDI?
How do they work?
Thiazide like diuretics
Hypothesised but thought to reduce whole body sodium so GFR is lower
What two cells are involved in acid base control at the DCT and CD?
What are their functions?
Alpha-intercalated cells: increased pH by reabsorbing HC03- and secrete H+
Beta-intercalated cells: decrease pH by HCO03- secretion and H+ réabsorption
How is HCO3- reabsorbed at the PCT?
How is new HC03- made in PCT?
H20 and C02 are converted into H+ and HC03-, H+ leaves the cell into the tubule via Na+/H+ antiporter and H+ATPase pump
HCO3- enters blood via Na+/HC03- symporter (na+ there from previous antiporter and Na+/K+/ATPase pump)
Glutamine first converted into NH4+, this leaves PCT cell as NH3, left over H+ leaves via H+/na+ antiporter and HC03- goes into the blood via diffusion
How much changed in blood volume is required for the hypothalamus to be alerted and produce vasopressin?
Where in the hypothalamus is vasopressin made?
10-15% via baroreceptors
In the supraoptic and paraventricular nucleus
