Reg of Na Balance & ECF Vol - Rao Flashcards
What determines plasma volume?
ECFV
What does plasma volume determine?
Mean circulatory filling pressure; therefore, cardiac output
What are the determinants of ECFV?
- Na+ Balance (directly proportional to total body Na Content
- ECFV is independent of Pna
What keeps Pna constant usually?
AVP-mediated water excretion by the kidneys
When does change in Pna occur?
Only when gain or loss of Na exceeds thirst mechanism and Kidney’s ability to correct the situation
What is your daily intake of sodium?
8-15 mgs or 150-250 meq
What are the three mechanisms of sodium loss and what percentage does each take care of?
Skin 0-20%
GI - 0.5-10 - diarrhea, vomiting
Renal - 80-90%
What are the consequences of sodium retention?
Retention of one day’s intake leads to retention of 1 L of water to maintain isotonicity. Increase in body weight by 1 kg (2.2 lbs)
What are things that can lead to a Na imbalance?
diarrhea, vomiting, excessive sweating, diuretics (i.e. bulimics abusing diuretics)
How many meq/day of Na are reabsorbed in the proximal tublue?
16000 (64% of filtered Na)
How many meq/day of Na are reabsorbed in the Loop of Henle?
7000 (28%)
How many meq/day of Na are reabsorbed in the distal tubule?
1750 (7%)
What are signs of a ecfv deficit?
Decreased in systemic bp (hypotension)
evident when standing, only when PV is significantly reduced.
What are signs of moderate to severe ecfv expansion?
Edema (lower limbs), requiring increase of 2.5-3 L
What can can a moderate to severe ecfv increase?
congestive renal failure, heart failure
What causes a more severe increase in ECFV?
Pulmonary edema
What heart sound is present in ecfv expasion?
s3 gallop, due to progressive increase in venous congestion
What physically can be seen in a person with ecfv?
distension of large veins in neck
When do you see edema with normal or low ecfv?
hypo-albuminemia
Explain the pathway that hypo-albuminemia causes edema/
dec albumin - dec colloid osmotic pressure - flux of fluid into isf - edema
What is a rapid response to plasma osmolarity change?
When someone has increased water intake, it produces diuresis, rapidly decreasing urine osmolarity to compensate. Once balance is restored, urine osmolarity will increase.
Does a small or large change have to present in plasma osmolarity for the body to decrease urine osmolarity?
a very small change in plasma osmo will lead to a huge change in urine osmol
What is a slow response to plasma osmolarity changes?
Renal Na+ excretory system (which takes 2-4 days)
Does increase salt increase decrease or increase ecfv?
increase
Hypertension patients are recommended to do what?
cut salt intake
Where are the receptors of ecfv located in the body?
localized in large veins atria and arteries
What are the neural stretch receptors?
In large veins, they respond to mechanism stretch due to venous distention. Signals to pituitary gland to regulate AVP/ADH -> regulates renal Na excretion
What are atrial stretch receptors?
Respond to distention, sends central signal via parasympathetic fibers in vagus nerve: variety of centers that are associated with AVP secretion, sympathetic firing to kidneys and cv centers
What does ANP do?
regulate renal Na excretion
How does each of the following affect Na:
GFR
Aldosterone
Natriuretic Hormone
Renin-Angiotensin
Incr GFR - Inc Na excretion
Aldosterone - Inc Ne reabs in DT and CD
Natriuretic Hormone - Decr Na reabsor
Renin-Angio Dec ECFV - Inc Na Reabso
If a change in GFR is very low, how can you determine that there has been a change
An increase in Na excretion
If you have a 50% increase in BP, how much will urine flow and Na excretion go up
3-5 fold
What stimulates Aldosterone secretion
plasma K and angiotensin,
Where does aldosterone work
dct and cd, increasing na reabsorption
What are the mechanisms of aldosterone?
increase open Na channel in DCT and CD, increase NACL cotrasnporter
Increased synthesis of NKA - increase Na reabsorption and K secretion
Increased syntehsis of Krebs cycle enzy,es - increased ATP synthesis
Does aldosterone have a slow or fast effect on Na reabsorption in dt and cd?
slow
What is the opposite of aldosterone? what’s it’s effect
Natriuretic Peptide
increased when Pna increases
what are the actions of ANP?
inhibits Na reabsoprtion, Increased GFR and Na excretion, inhitibts aldosterone secretion
Where does renin come from?
JG cells
what are the direct effects of angiotensin ii?
stimulates aldosterone release from adrenal cortex and induces na reabsorption
He has two great charts that lay everything out for you
yea
