renal physiology Flashcards
what are the 2 substances that can be used to measure fluid compartements ?
inulin
radiolabeled albumin
when does fluid compartment shift happen ?
only when there is a difference in osmolarity
what are the examples of isotonic fluid loss ?
hemorrhage
what happens if you infuse 5% dextrose ?
initially isotonic
but then the glucose is taken up by the cells
leaving behind a hypotonic fluid and makes the cells swell
used to hydrate cells
what happens after the administration of mannitol ?
mannitol is an alcohol sugar and does not enter the cell
means that the osmolality is higher in the extra cellular space
water rushes out of the cell
and causes the cell to shrink
used to decrease the pressure - especially in ICP and glaucoma
what is the effective circulating volume ?
the extracellular fluid contained in arterial system that maintains tissue perfusion
not the same as total volume
what is the extracellular circulating volume affected by ?
volume
cardiac output
vascular resistance
what are the consequences of low ECV ?
low blood pressure
activated the RAAS
sympathetic nervous system
what is the total body water vs ECV in heart failure and in cirrhosis ?
heart failure patients and cirrhosis patients have an increased total body water but a decrease in effective circulating volume
how do we evaluate kidney function ?
GFR
renal blood/plasma flow
filtration fraction
what are the filtration driving forces determining the GFR ?
the hydrostatic pressure and the oncotic pressure
what is the difference in function between oncotic pressure and hydrostatic pressure ?
oncotic pressure - derived from albumin and pulls fluid in
hydrostatic pressure - force pushing water out
what are the ways to increase the GFR ?
dilate afferent arteriole
constricting the efferent arteriole
what are the ways in which the GFR can be decreased ?
an increase in plasma proteins
ureter obstruction
what are the mechanisms in which autoregulation of the kidney can happen ?
through myogenic mechanism
tubuloglomerular feedback
what is the myogenic mechanism of the kidneys ?
afferent arteriole constricts with high blood pressure
what is the tubuloglomerular feedback ?
depends on the macula densa - if it sense a high level of NaCl that means theres high blood pressure and hencea high GFR , to decrease this , the macula densa sends signals to the afferent arteriole to constrict
if the macula densa senses too little NaCl it sends signals to the afferent arteriole to relax and increase the GFR along with activation of the JGC allowing the release of renin and activating the RAAS and hence increasing the blood pressure
