The glomerular filtration rate (GFR) will decrease if:?

Question

A) The amount of waste products in the blood increases

B) The amount of waste products in the blood decreases

C) blood flow through the kidneys decreases

D) blood flow through the kidneys increases

Answer 1

C) blood flow through the kidneys decreases

Poor kidney perfusion can lead to build up of toxins in the blood.

As an aside:

If bp increases, this would have the effect of increasing the GFR.

Answer 2

an increase in systemic blood pressure will increase GFR so I am going to say D.

that other guy is wrong.

Answer 3

C

GFR is only dependent on the amount of blood flow over a period of time, so A and B are out.  

D is obviously not right, leaving you with C.

dude below me clearly misread the question.

Answer 4

C) blood flow through the kidneys decreases.

The GFR decreases when the blood pressure in the afferent arteriole increases. Vasoconstriction of the afferent arteriole  increases blood pressure and decreases blood flow into the glomerulus. This will cause glomerular capillary blood pressure to decrease and this in turn decreases the net filtration pressure at the glomerulus. Hence, GFR decreases.