Cliff glom filt

(The FASEB Journal. 2003; 17(5):A816)

Probing Student Understanding of Glomerular Filtration.

William Cliff,1 Mary Pat Wenderoth,2 and Joel Michael3
1Dept. Biology, Niagara University, Lewiston, NY 14109, 2Zoology Dept., Univ. of Washington, Seattle, WA 98195, 3 Molecular Biophysics and Physiology, Rush University, Chicago, IL

We were interested in student understanding of relations between solute concentrations in the plasma and filtrate, glomerular filtration rate (gfr), and permeability across the glomerular wall.  Students who had completed renal physiology were asked to predict and explain the qualitative change in glucose filtrate concentration following an increase in the plasma concentration and no change in gfr.  Of 125 students tested, 68% correctly predicted increased filtrate concentration, 25% predicted no change and 7% predicted decrease.  Of students answering correctly, some indicated that both plasma concentration and gfr influenced the filtrate glucose concentration.  A new survey using a quantitative predict-and-explain question was designed to better identify this misconception.  In this survey, only 42% of students correctly predicted that the filtrate concentration would equal the final plasma concentration, 31% predicted an intermediate concentration between the initial and final plasma concentrations, 10% predicted a higher concentration, and 17% predicted no change (n=146).  Thus, a substantial fraction of these students (41%) would have answered the qualitative query correctly yet respond incorrectly to a quantitative query about the same concept.  These results show that the notions that these students have about solute filtration are incompletely integrated after instruction in renal physiology.  Our study also shows the utility of a sequence of diagnostic probes to uncover different facets of student understanding of physiological concepts. (Supported by NSF REC9909411)

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