How does the vessel diameter of the afferent arteriole change in order to decrease glomerular hydrostatic pressure (GHP) and restore the glomerular filtration rate (GFR) to normal

The afferent vessel will generate vasodilation, that is, increase its diameter to generate a stirring effect in the glomerulus, promote glomerular filtration and decrease pressure in it.

Explanation:

The renal glomeruli are in charge of filtering the blood.

They have an efferent vessel that collects the blood to be filtered and an afferent that is in charge of returning it to the bloodstream of systemic circulation.

When the pressure of the glomerulus is very high, the glomerular filtration rate is increased and it needs to be regulated, that is why the afferent vessel undergoes vasodilation to decompress the glomerulus pressures and thus regulate the filtration rate by decreasing it.