Arteriole leading into the
glomerular capillary. It is the location of the
juxtaglomerular cells as well as
intrarenal baroreceptors. At first glance, it is merely a blood vessel, but with the help of the aforementioned
JG cells and the
macula densa, as well as the
sympathetic nervous system, it regulates the pressure and therefore the flow of
blood entering the
glomerular capillary. This regulation is done mostly via the
renin-angiotensin system, where
vasoconstriction is caused by
angiotensin II.
Through these mechanisms, the glomerular filtration rate is regulated in such a way that it does not change substantially unless the systemic arterial pressure is less than 80 mmHg or greater than 180 mmHg.
These are my interpretation of my lecture notes, but I may have used some references from Hole's Anatomy and Physiology (Shier, Butler, Lewis) and Human Physiology (Vander, Sherman, Luciano)