Renal lecture 3 regulation of sodium balance Flashcards
Why is total body balance of Na and water important (to sustain what)?
-Total-body balance of Na and water has to be maintained to sustain normal blood pressure and life.
What accounts for the majority of output?
How do you calculate insensible loss?
urine at 1500mL, only part that can be regulated
insensible loss=900- metabolic production (intake side)
What has a large and small contribution to output in grams?
sweat and feces are both 0.25 g each
and urine account for 10.0g and it is the predominant NaCl output
What are we in a balance of?
How much can water and NaCl output vary?
-water output can vary from 0.4 L/day to 25 L/day
-sodium chloride output can vary from 0.05 g/day to 25 g/day.
How much of Na and water are reabsorbed?
Where is the majority of reabsorption occuring?
Where does the major hormonal control of reabsorption occur in the kidney?
-Both sodium and water are freely filtered but ~99% is reabsorbed (no secretion)
-The majority of sodium and water reabsorption (~2/3) occurs in the proximal tubule
-major hormonal control of reabsorption occurs on the DCT and CD
What type of process is sodium reabsorption, where does it occur?
What is the process used for water reab. and what does it depend on
-is an active process occurring in all tubular segments (except the descending thin limb of Henle’s loop)
-Water reabsorption is by diffusion and is dependent upon sodium reabsorption
What do the active Na+/K+ ATPase pumps do oon the basolateral membrane?
-Active Na+/K+-ATPase pumps transport sodium out of
the cells and keep the intracellular concentration of sodium
low
What happens to movement of sodium on the apical (luminal) membrane?
What are examples of the different mechanisms?
-Sodium moves downhill from the tubular lumen into the
tubular epithelial cells.
-Each tubular segment has different mechanisms:
In the proximal tubule: Na+-H+ antiporter (counterporter)
Na+-glucose cotransporter
In the CCD: diffusion via Na+ channel
What is the major site of Na reab.
What does the Na+/K+ pump in/out to where?
How many Na+ are lost vs K+ gained in the NaK ATPase pump?
-cortical collecting duct
-pumps in K+ and pumps out Na+ into the interstitium
-loses 2 Na+ and gains 1K+
how does sodium intake regulate urinary sodium excretion?
- Na+ intake decrease, Na+ urine excretion decreases, and vice versa for an increase in Na+
How can we sense Na+ in the body without a sensor?
-amount of Na+ dictates the amount of extracellular volume, so we have ECF volume sensor, so the amount of Na+ is indirectly detected using baroreceptor in the plasma membrane
What do changes in Na+ causes in the body?
-Sodium is the major extracellular solute, thus changes in total body sodium result in similar changes in extracellular fluid volume
How much of total body water (60% Bw) is intracellular fluid vs extracellular?
-intracellular fluid=40% of Bw
extracellular fluid=20% of Bw—>3/4 intersitial fluid and 1/4 plasma
What is plasma concentration not a marker for?
What does PNa reflect?
Plasma concentration of sodium is NOT a marker for total body sodium
-PNa only reflects the relative relationship of total body Na and
water
What happens to GFR when there is an increase in sodium and water loss due to diarrhea?
-increased constriction of afferent arterioles
-decreased net GF pressure and a decrease in GFR, allowing for decreased Na+ and H2O excretion
What happens to plasma volume, venous pressure, stroke volume, etc when we have increased Na+ and H2O loss due to diarrhea?
Where is the percent Na reabsorption in the kidney?
in proximal tubule=67%
-thick ascending limb=25%
-distal tubule=4%
-CCD=3%
-IMCD=1%
What increases in the presence of aldosterone?
-Na+ absorption increases in presence of aldosterone
What does the liver, kidney and adrenal cortex secrete?
-liver-secretes angiotensin
-kidneys-secrete renin
-adrenal cortex-secretes aldosterone
What does renin regulate?
What convertes Ag1 to Ag2 in the renin agiotensin system?
-regulates amount of angiotensin 1
-angiotensin converting enzyme
where is the juxtaglomerular appartus near?
What specific cells secrete renin?
What has a special signaling capacity in the tubular lumen to renin, what does this stimulate?
-next to glomerulus
-juxtaglomerular cells secrete renin
-macula densa, and this stimulates aldosterone
What happens to regulation of renin secretion when we have a decrase in plasma volume?
How does this affect nerve activity, arterial pressure, GFR, and renin secretion?
increase activity of renal sympathetic nerve
-decrease in arterial pressure (less stretch)
-decrease in GFR which causes decrease in macula densa
-increased renin secretion,etc
What is the action of ANP as the plasma volume increases?
What happens to cardiac atria, GFR and tubules?
