Unit 7 - Regulation of Plasma Sodium and ECF Volume Flashcards
why is maintaining plasma volume so important?
blood pressure drives blood flow, and blood pressure is dependent on volume
-so volume –> BP –> flow
what are the sensors, efferent pathways, effectors, and regulated parameters of osmolarity?
S: hypothalamic osmoreceptors
EP: ADH and thirst
E: kidney, brain (thirst)
RP: renal free water excretion, water consumption
what are the sensors, efferent pathways, effectors, and regulated parameters of ECF volume?
S: carotid sinus, aortic arch, renal afferent arteriole, and atria (actually pressure stretch receptors)
EP: renin-angiotensin-aldosterone, SNS, ADH, ANP (virtually never constant)
E: short term heart and blood vessels, but long term kidney
RP: short term blood pressure (PVR x CO), but long term renal Na excretion
what is the renal response to abrupt increases in dietary Na (to 150 mmol)?
if initially in Na+ balance, and Na+ intake is increased, the kidney takes 6 days to catch up (positive balance) by retaining osmolarity by retaining 1 L water (gain 1 kg weight)
what is the renal response to abrupt decreases in dietary Na (by 150 mmol)?
if initially in positive Na+ balance, and Na+ intake is decreased, the kidney takes 6 days to recover (negative balance) by retaining osmolarity by losing 1 L water (lose 1 kg weight)
what is hemorrhage an example of and what will it cause?
severe ECF volume contraction
-induces decrease in GFR
is kidney’s increase in Na+ excretion in response to an increase in ECF volume, or an increase in Na+ concentration?
it’s due to increase in ECF volume
-will increase excretion to retain osmolarity at 300 mmol/L (both 150 mmol Na+ and 150 mmol Cl-)
what is effective circulating volume? what does it do?
functional, not anatomical, blood volume reflecting extent of tissue/organ perfusion where blood pressure is sensed
- induces regulation of Na+ excretion
- normally paralleles total ECF volume, both intra- and extra-vascular volumes
which induces regulation of Na+ excretion: changes in effective circulating volume, or total ECF volume?
changes in effective circulating volume
when is effective circulating volume less than total ECF volume?
in disease states that cause edema (like CHF)
what is CHF in regards to edema?
increases end diastolic pressure, so increased capillary hydrostatic pressure driving fluid from intravascular to extravascular space
what does pulmonary edema cause volume-wise?
if secondary to left ventricular heart failure and pulmonary HTN
-caused by increased capillary hydrostatic pressure in the lung, driving fluid from intravascular to extravascular space, that severely compromises gas exchange in lung
what does liver disease do volume-wise?
caused by decrease in synthesis of albumin, so decreased plasma oncotic pressure that upsets normal Starling forces
what does neprhotic syndrome do volume-wise?
disease of renal glomerulus allows inappropriate filtration of albumin = albuminuria
-decreases plasma oncotic pressure, disrupting Starling forces
what do diuretic drugs do?
decrease plasma volume by “forcing” kidney to increase excretion of Na+ and water in urine
-this decreases hydrostatic pressure, and increases oncotic pressure in capilliaries, which favors absorption of edema in interstitial space back into intravascular space
what are the 3 types of ECF volume baroreceptors?
- “central” vascular sensors
- Low pressure (very important): atria and pulmonary vasculature
- High pressure (less important): carotid sinus, aortic arch, and juxtaglomerular apparatus (renal afferent arteriole) - sensors in CNS (less important)
- sensors in liver (less important)