Regulation of Glomerular Filtration Rate - Overview
The
Kidneys' objective is to maintain homeostatatic balance of blood volume, pressure, and ion concentrations via filtration of the blood, despite fluctuations in blood pressure throughout the day.
GFR regulation achieves this balance through both intrinsic and extrinsic mechanisms.
GFR is most easily regulated by adjusting the
net filtration pressure, which is determined by the hydrostatic and oncotic forces at the filtration membrane.
Involve intra-renal mechanisms; structures within the kidneys initiate the
intrinsic mechanisms.
Intrinsic mechanisms dominate as long as
MAP is 80-180 mmHg.
The goal is to maintain nearly constant GFR over a wide range of mean arterial pressures.
Includes myogenic and tubuloglomerular feedback, which act primarily on afferent arteriole.
Involve
neural and hormonal mechanisms; requires transport of neurotransmitters/hormones in bloodstream.
Active when MAP is below 80 mmHg.
The goal is to maintain blood volume and pressure; regulation of GFR is one facet of this.
Sympathetic response acts primarily on afferent arteriole (Norepinephrine).
Hormonal response acts primarily on efferent arteriole (Angiotensin II).
