• View in gallery

    The simulation shows the students the size of the efferent and afferent arterioles, GFR values, capillary pressure, and the direction of the net pressure within Bowman’s capsule.

  • View in gallery

    When a student increases the blood pressure and makes the glomerular filtration barrier permeable to proteins, GFR is increased. Proteins can permeate this barrier and enter Bowman’s space in conditions such as diabetes and hypertension, which make oncotic and hydrostatic pressure additive forces in the Starling equation.

  • 1.

    Stevens LA, Levey AS. Measurement of kidney function. Med Clin North Am 2005; 89:457473.

  • 2.

    Hall JE, et al.. Control of glomerular filtration rate by renin-angiotensin system. Am J Physiol 1977; 233:F366F372.

  • 3.

    Hostetter TH, Troy JL, Brenner BM. Glomerular hemodynamics in experimental diabetes mellitus. Kidney Int 1981; 19:410415.

  • 4.

    Carlström M, Wilcox CS, Arendshorst WJ. Renal autoregulation in health and disease. Physiol Rev 2015; 95:405511.

  • 5.

    Zhao L, et al.. High-salt diet induces outward remodelling of efferent arterioles in mice with reduced renal mass. Acta Physiol (Oxf) 2017; 219:654661.

Using a Computer Simulation to Teach Undergraduate Students the Principles Behind GFR Autoregulation

  • 1 José J. Reyes-Tomassini is a visiting assistant professor at Wartburg College in Waverly, Iowa.
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The concept of glomerular filtration rate (GFR) and its regulation is central in renal physiology. Estimates of GFR are often used in the clinical setting to assess kidney health. GFR is an effective measure of kidney function (1). Many pathophysiologic conditions affect GFR by altering the glomerular capillary pressure, including diabetes mellitus and essential hypertension. Afferent and efferent arteriole resistance plays a crucial role in the regulation of GFR. Whereas dilation of the afferent arteriole causes an increase in GFR, dilation of the efferent arteriole decreases GFR (2, 3). The concept is familiar to

The concept of glomerular filtration rate (GFR) and its regulation is central in renal physiology. Estimates of GFR are often used in the clinical setting to assess kidney health. GFR is an effective measure of kidney function (1). Many pathophysiologic conditions affect GFR by altering the glomerular capillary pressure, including diabetes mellitus and essential hypertension. Afferent and efferent arteriole resistance plays a crucial role in the regulation of GFR. Whereas dilation of the afferent arteriole causes an increase in GFR, dilation of the efferent arteriole decreases GFR (2, 3). The concept is familiar to all nephrologists, but can be challenging to explain to nursing and other students.

Simulations are a great way to introduce students to basic physiologic concepts. Simulations that feature graphics are especially useful to relate these concepts. I have developed a computer simulation that uses animations and graphics to show the basic concepts underlying GFR control. The program also simulates autoregulation by changing the size of the afferent and efferent arterioles. By use of a recursive algorithm, the simulation alters afferent and efferent arteriole resistance to move GFR toward normal while maintaining renal blood flow. The efferent arteriole is thought to be less involved in autoregulation but is thought to be the target of some hypertensive drugs (4).

The role of permeability to proteins on transglomerular pressure is also simulated. By sliding a control on the simulation, users can change the permeability of the glomerulus to proteins and observe what occurs when proteins, such as albumin, pass intact through the glomerular barrier. This can happen in some chronic diseases such as hypertension and diabetes.

Users can increase or decrease blood pressure by moving a slider control. Users can also turn off autoregulation and manually control the diameter of the efferent and afferent arteriole. Changes in renal blood flow are shown visually by changing the color of the blood flowing through the glomerulus and by an indicator bar. The relative difference between the afferent and efferent arterioles is shown both in the animation of the glomerulus and in a separate figure that shows the relative difference between the two arterioles.

Since I began using this in my classroom to teach this section of kidney physiology, I have found that students do well on the concept of GFR and can articulate the relationship between afferent and efferent arteriole resistance and GFR and also the relationship between blood pressure and unregulated GFR. Student feedback on the use of this simulation has been overwhelmingly positive.

The program runs in any Windows 95 or higher system. It was written in Visual Basic 6.0. I plan to make a game version of the program. If you have suggestions or ideas or if you would like to use this simulation in your classroom or for other educational purposes, you may reach me at jose.reyestomassini@wartburg.edu.

The program is free and available upon request.

Figure 1.
Figure 1.

The simulation shows the students the size of the efferent and afferent arterioles, GFR values, capillary pressure, and the direction of the net pressure within Bowman’s capsule.

Citation: Kidney News 10, 6

Figure 2.
Figure 2.

When a student increases the blood pressure and makes the glomerular filtration barrier permeable to proteins, GFR is increased. Proteins can permeate this barrier and enter Bowman’s space in conditions such as diabetes and hypertension, which make oncotic and hydrostatic pressure additive forces in the Starling equation.

Citation: Kidney News 10, 6

Suggested Reading

  • 1.

    Stevens LA, Levey AS. Measurement of kidney function. Med Clin North Am 2005; 89:457473.

  • 2.

    Hall JE, et al.. Control of glomerular filtration rate by renin-angiotensin system. Am J Physiol 1977; 233:F366F372.

  • 3.

    Hostetter TH, Troy JL, Brenner BM. Glomerular hemodynamics in experimental diabetes mellitus. Kidney Int 1981; 19:410415.

  • 4.

    Carlström M, Wilcox CS, Arendshorst WJ. Renal autoregulation in health and disease. Physiol Rev 2015; 95:405511.

  • 5.

    Zhao L, et al.. High-salt diet induces outward remodelling of efferent arterioles in mice with reduced renal mass. Acta Physiol (Oxf) 2017; 219:654661.

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