Renal Control of Blood Flashcards
What is glomerular filtration and reabsorption driven by?
Filtration is driven by hydrostatic pressure - the pressure difference across glomerulus. Depends on blood pressure and arteriolar constriction/dilation.
Reabsorption is driven by osmotic presure.
What is glomerular filtration rate dependent on?
Permeability of membrane
Surface area of membrane
Filtration pressure.
The smaller the afferent arteriole, the lower GFR is.
The larger the afferent arteriole, the higher GFR is.
The smaller the efferent arteriole, the higher GFR is.
What does the glomerulus filter out, as opposed to the rest of the nephron?
The glomerulus filters out large componds - cells and protein complexes.
The rest of the nephron is repsonsible for reabsorbing water, ions etc.
Through what channel is water reabsorbed?
Through aquaporins.
Open aquaporins = concentrated urine.
Closed aquaporins = dilute urine.
What are the three ways in which we regulate blood volume?
Through stretch-gated baroreceptors that sense venous pressure and release ANP on stretch, blocking Na+ reabsorption causing loss of water and decreasing blood volume.
Through osmoreceptors that sense increased osmolarity, releasing ADH to open aquaporins.
Through tubuloglomerular feedback - another flashcard.
How does tubuloglomerular feedback work?
Juxtaglomerular apparatus senses speed of GFR.
If blood is going through tubules too slow (bc of low BP), not enough NaCl is reabsorbed.
This causes renin to be released, activating the RAAS, increasing salt reabsorption and vasoconstriction.
Opposite for if GFR is too high - too much salt is pumping in, so renin is not released and RAAS shuts off, causing decreased reabsorption of salt and vasodilation.
