How does the juxtaglomerular apparatus respond when systemic blood pres- sure is too high? A. the juxtaglomerular cells send a message to the afferent arteriole to dilate. B. The macula densa sends a message to the efferent arteriole to constrict. C. The macula densa sends a message to the afferent arteriole to constrict. D. The granular cells release renin which causes systemic arterioles to constrict.
Option C. Constricting the afferent arteriole will lower the quantity of blood coming into the glomerulus and therefore the blood pressure in it. All other selections will bring about an increase in pressure in the glomerulus.
