The Clearance Principle and Regulation of Glomerular Filtration Rate

Glomerular Filtration RateRate at which plasma is filtered by the renal glomerular capillaries

Inulin

Non toxic fructose polymerFreely filtered by the glomeruliNot reabsorbed or secreted by the kidney tubulesquantity of inulin filtered=quantity of inulin excreted

GFR

Amount of inulin filtered per unit time=Plasma inulin concentration X GFR

1. afferent arteriolar feedback mechanism2. efferent arteriolar feedback mechanismdependent upon special anatomical arrangements of the juxtaglomerular apparatus

Ability of individual blood vessels to resist stretching during increased arterial pressure.
Contributes to the maintenance of constant renal blood flow and GFR

=GFR/ERPFrepresents the fraction of plasma that filters through the glomerular membrane and appears as primary urine in Bowman's capsule

1. acts to decrease afferent arteriolar resistance in order to raise GRF back to normal2. Increases renin release to increase efferent arteriolar resistance and return GFR to normal

ADH-->decrease water excretionAldosterone-->renin-->decrease sodium excretion

Constricts efferent arterioles of the kidneys to raise GFRStimulates release of aldosterone from the adrenal cortex