Body Fluid Volume Maintenance Flashcards
Rule of Na balance
Input = Output
Positive Na balance
input > output
Negative Na balance
output > input
When you’re in +/- Na balance, which compartment is affected?
ECF volume will expand/contract, has nothing to do with plasma sodium concentration
**CHANGE IN NA+ IS EQUIVALENT TO ECF VOLUME
effective circulating volume is related to adequate perfusion of vascular beds (brain, heart, and other vital organs) and is dependent on these 3 factors
- cardiac output
- MAP (BP)
- vascular volume (plasma) (that gets pushed into vital organs)
ECV sensors
high pressure: carotid sinus, aortic arch, juxtaglomerular apparatus in kidney (HGA)
low pressure: pulmonary vessels, atria
Changes in ECV will be picked up by volume sensors, which then send these 4 important signals to the kidney. List the ones that respond to increases in ECV and to decreased ECV.
Increased ECV: atrial natriuretic peptide (ANP) –excretin sodium
Decrease ECV: SNS, RAAS, and ADH (from posterior pituitary)
An increase in sympathetic nervous system (increases/decreases) 5 important things
- increases cardiac output
(beta1 receptors, inotrophy, chronotropy, lusitropy) - increases vascular tone (alpha1 receptors, constricts and increases resistance on arteriole side and venous side, moves blood from venous to circular side to increase preload)
- Decreases RPF and GFR (constricts afferent arteriole, decreases glomerular pressure, decreases filtration) causes….
- decrease in NaCl excretion
- increase renin release
Function of renin, and where is it released?
angiotensinogen —renin—> angiotensin I –ACE–> Angiotensin II
renin is rate limiting step release from JG cells in kidney
3 factors causing renin release from JG cells
- SNS
- Baroreceptor type phenomenon in JG cells - increase pressure, increase stretch, alters renin release
- direct input from macula densa - sense alteration in electrolyte distribution
An increase in SNS causes an (increase/decrease) in renin release
increase in renin release
a decrease in MAP causes an (increase/decrease) of renin release
increase (decrease in MAP causes a decrease in arteriole stretch, renin is released, causing an increase in MAP, an increase in AA stretch, and a decrease of renin release)
in what situation does the macula densa cause a direct increases of renin release?
when the macula densa receives a decrease in solut delivery
what feedback loop causes a decrease in renin release?
Angiotensin II
Function of aldosterone and where in nephron and what channels
increases Na reabsoprtion in CD (principal cell)
- increases Na channel (reabsorption on apical side)
- increases K channel (increased secretion due to paracellular transport of Cl)
- increases ATPase on basal side
long term: increases the number of transporters/channels by acting on TFs
renal effects of AII
change in RPF/GFR and increases NaCl reabsoprtion in PT
extrarenal effects of AII (4)
potent vasoconstrictor, increases aldo release, increases ADH release, increases thirst
Euvolemia
normal ECV volume, input = output
major player during euvolemia
aldosterone in CD
filtered load of Na
GFR x P(Na)
The goal of maintaining constant NaCl delivery to the CD is done by these two factors
- autoregulation (MAP vs flow)
2. glomerulotubular balance