That’s a sin wave. It’s my precious graph, I try to sound like Golem from Lord of the Rings when I introduce it. I draw it on the board after my students try to balance a meter stick with one finger (they wear goggles, of course). I have the students draw the sin wave and we talk about how the meter stick moved one direction, and they moved their hand the opposite direction and we laugh about how difficult it is to balance the meter stick and at how irritated the class below us must be after hearing all the dropped meter sticks. I don’t label the y-axis, but I call the x-axis the set-point, which represents the meter stick standing in perfect balance. As long as the meter stick doesn’t go too far to the right (above the line) or too far to the left (below the line), we can keep it on our hands, if it goes too far (past the curve), the meter stick falls. We then label the peaks of the curve and dotted lines parallel to the set point line and we call the distance, normal limits.
The graph forms the basis of how we study physiology in my class. I introduce a new factor every week and students have to explain how it relates to the graph. Sometimes the factor is a mineral or a vitamin, sometimes it’s a variable like heart rate or breathing depth. We relate everything that has some sort of homeostatic control to this graph. Blood sugar, pH, salt levels in extracellular fluid, hormones, nutrients – they all have to relate to the graph. Every organ has a function related to the graph, and students write about this graph in relationship to daily experiences such as getting too much or too little sleep or having too much or too little space between themselves and whomever they are talking to. Eventually students come to see how this graph relates to negative feedback and maintaining the endless cycles that the human body experiences in a lifetime. Sometimes the graph is not symmetrical and sometimes it’s two waves separated in time to examine cause and effect. Sometimes the graph seems like a natural fit, sometimes it’s forced, but the point is its consistency and the framework it provides for asking questions. It teaches my students to expect that whatever happens to raise a variable, will be counteracted in some way to bring it back down. This graph is a sin wave, I did not invent it (by ifland). This graph was never my idea, applying physiology to this graph was not my idea (I truly cannot remember who taught me this), but using it, and using it regularly, has impacted my teaching as much as designing curriculum, examining scope and sequence, using reading strategies, and even using technology. What’s more, I am completely open to my sin wave not being the best idea or the best tool in the shed – it’s just what works now, it could very well change.
I’m curious, what’s your graph? What’s the constant in your teaching, that little tool, or protocol that helps you communicate the material and helps your students understand it? It may be as simple as what a popular sixth grade teacher does on her whiteboard every morning “if it’s in blue, it’s what you must now do…,” but share it with your colleagues, share it on this blog, because collectively these little algorithms and ideas become what we call best practice, and our students deserve that.
Dan Bartsch is a National Board Certified biology instructor and department chair at Billings Senior High School in Billings, MT. He has served as a LifeSciTRC Scholar and Fellow. Dan has been teaching for over 20 years and feels blessed to be part of such a great endeavor.