Normal filtration fraction is around:: (A) 0.05, (B) 0.1, (C) 0.2, (D) None of the above
Answer is C. The ratio of the GFR to the RPF, the filtration fraction, is normally 0.16 to 0.20. The GFR varies less than the RPF. When there is a fall in systemic blood pressure, the GFR falls less than the RPF because of efferent aeriolar constriction, and consequently the filtration fraction rises. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 38.