Renal 8 Hormonal Regulation of Body Salts Flashcards
What 3 ions are the major determinants of ECF osmolality ?
Na+, Cl- , HCO3-
What is the major determinant of ECF volume?
ECF osmolality
What happens to osmolality and ECF when you increase Na+?
^ Na»_space; ^ osmolality»_space; ^ water reabsorb.»_space; v osmolality and ^ ECF
What happens to osmolality and ECF when you decrease Na+?
v Na»_space; v osmolality»_space; v water reabsorb.»_space; ^ osmolality and v ECF
What does positive Na balance mean for intake and excretion and ECF?
Na intake > Na excretion, ECF increases, increasing body weight
What does negative Na balance mean for intake and excretion and ECF?
Na intake < excretion, ECF decreases, decreasing body weight
Normally, how do the kidneys keep ECF volume constant?
adjusting excretion of Na and Cl
What is effective circulating volume? (ECV)
ECV reflects the portion of ECF volume within the vascular system that is effectively perfusing the tissues
How do changers in ECF affect arterial pressure and cartiac output
They are sensed as changes in ECV and change directly.
so v ECF means lower AP and CO
When ECF is increased, what happens to arterial pressure and cardiac output?
Both increase as it is sensed as increased ECV
When ECF is decreased, what happens to arterial pressure and cardiac output?
Both decrease as it is sensed as decreased ECV
How does pulmonary vasculature engorgement lead to water diuresis?
engorgement => v sympathetic and v ADH => water diuresis
Are the cardiac atrial stretch sensors for low or high pressure?
Low pressures (Venous side of circulation)
What gets released with cardiac atrial stretch and what does it cause?
ANP and natriuresis
Are the aortic and carotid sinus baroreceptors for low or high pressure?
High pressures (arterial side)
What happens when the aortic arch and carotid sinus baroreceptors are stimulated?
decrease s ympathetics and decrease ADH
What does very slow tubular flow cause?
stimulation of JGA (juxtaglomerular apparatus) -> ^ renin
What are the hepatic sensors
^ liver pressure receptors => v sympathetics and ^ Na+ secretion
^portal vein Na+ sensors => v sympathetics and ^ Na+ excretion
What happens to Na excretion when there is higher [Na+] in the CSF?
decreased sympathetics and higher Na excretion
Does the RAA system promote salt retention or excretion?
Promotes salt retention
Does ANP promote salt retention or excretion?
Excretion
How does the negative feedback system eventually activate renin to increase ECV after an initial decrease?
v ECV => v AP and ^ sympathetics => v renal perfusion => v fluid delivery to macula densa => ^ renin
What does renin do by itself?
convert angiotensinogen to Angiotensin I
What does ACE do?
converts angiotensin I to Angiotensin II
What do angiotensinases do?
convert AT-II to AT-III
What does AT-II do?
stimulates ADH release from post. pituitary and thirst
stimulates aldosterone release from adrenal cortex under influence of ACTh (WITH AT-III)
What does aldosterone do?
circulates to the kidney where it binds to intracellular receptors signaling the production of new Na/K ATPase pumps in the DT and CD
What happens to sodium when Na/K pump activity increases?
Na+ reabsorption increases
What happens to potassium when Na/K pump activity increases?
Potassium secretion and excretion both increase
What is required for Na+ reabsorption to also promote water reabsorption?
Presence of ADH
What is the source of atrial natriuretic peptide?
syntheized and released in cardiac atria by myocytes
What is urodilatin?
natriuretic peptide produced endogenously in kidney
What promotes ANP release?
^ ECF volume
^ arterial pressure causing ^ left atrial pressure
^ venous pressure causing ^ R atrial pressure
What are the effects of increased ANP
decrease sympathetic:
=>v ADH =>water diuresis
=>^GFR => ^tubular load Na+ => ^ Na+ Excretion
v aldosterone => v Na+ reabsorption
v renin => v AT-II => v aldosterone => v Na+ reabsorption
What is euvolemia?
net 0 Na balance when excretion matches intake
During euvolemia, how much of the filtered Na+ load is reabsorbed?
99% (67% in PT, 25% in thick ascending limb, rest in DT and CD for fine control)
During euvolemia, which parts are under coarse control and which are under fine control for Na+ balance
PT and TAL are coarse control.
DT and CCD are fine control.
What is the mechanism for adjusting Na+ reabsorption to GFR fluctuations in PT?
Na+ reabsorbed load proportioned to Na+ filtered load (GT Balance)
What is the mechanism for adjusting Na+ reabsorption to GFR fluctuations in TAL (Thick ascending limb of Henle)?
Na+ reabsorption rate proportioned to Na+ delivery rate
What is the mechanism for adjusting Na+ reabsorption to GFR fluctuations in DT, CCD, IMCD?
Na+ reabsorption rate simulated by increased Na+ load
What are the 3 integrated responses of the nephron to increased ECV(Effective Circulating Volume)?
Increased GFR
decreased Na+ reabsorption in PT
decreased Na+ reabsorption in CD
What are the 3 integrated responses of the nephron to decreased ECV(Effective Circulating Volume)?
decreased GFR
increased Na+ reabsorption in PT
increased Na+ reabsorption in CD
What happens to ECV and plasma volume when fluid is lost to the interstitium?
v ECV and v plasma volume with no change in body weight
pulmonary edema, pleural effusion, ascites, pitting edema of ankles
How does increased venous pressure eventually lead to NaCl reabsorption?
^ venous pressure => ^ capillary hydrostatic pressure => ^ fluid movement into interstitium => v plasma volume => v ECV detected by baroreceptors => ^ symp. activity => ^ reabsorption of NaCl and H2O
If too much then this can repeat over until fluid into intertitium is extreme, causing edema
What is the starling force equation?
flow = Kf * (Pc-Pi-pic + pii)
What two components of starling forces are the most common causes of generalized edema?
increased capillary hydrostatic force
decreased capillary oncotic force
