Question

what happens to the glomerular capillary pressure and GFR when you decrease the afferent radius? increase it? why do you suppose this occurs?

Answer 1

When we decrease the radius of afferent arteriole the Glomerular capillary pressure and GFR decreases. When we reduce the afferent arteriole vessel radius the blood reaching the glomerular capsule decreases. Thus the glomerular capillary pressure decreases. We know that the glomerular capillary pressure is the driving force of the filtrate formation. So as the pressure decreases the GFR decreases.

When the radius of afferent arteriole increases glomerular capillary pressure and GFR increases. So when radius increases the blood reaching the glomerular capillary increases and this directly leading to the increase in pressure there. Thus the pressure increase leads to increase in GFR