Thermoregulation is a concept I teach to my 14-year-old students as part of an IGCSE course. As the content—sweating, shivering, & vasodilation—is relatively concrete, I could simply teach their effects in isolation. For example, "shivering causes heat gain when body temperature decreases". This alone is probably enough to gain some marks on an exam.
But, this would be missing an opportunity to develop our students understanding of systems. The more students practice thinking with systems theory, they more they can transfer it to other biological contexts and understand those in a deeper way. Its a positive feedback loop.
So let me show you how I taught this topic with a system dynamics model. This concept took two 50 min lessons.
Building a system dynamics model to *think with*
I always begin building a model with a stock and ask the students what the inflows and outflows would be. For another example of how I build the model, see this post.
Research suggests that students are much more likely to consider inputs, but not outputs, so I like beginning here because it focuses my students' attention on flows and accumulations in the system.
The only way to cause a change to the heat accumulated in the body is to adjust the inflow and outflow rates. Logically then, the next step is to ask students to identify the factors that affect the inflows and outflows. I would ask them to discuss it in pairs for half a minute or so, before hearing their ideas.
With this example being familiar (through our embodied experience), it's relatively easy to get some ideas from students, such as shivering and sweating. The key now is to have students make the distinction between factors that affect heat gain and loss. In my experience, students need time to think, a brief discussion in pairs, and possibly further teacher guidance.
Some students might get confused about what sweating actually does, but asking them to think about the contexts in which they sweat triggers understanding. Sweating then can be added to the model as a factor that increases heat loss.
As routine has it, I'll add the arrow between the factor and the outflow and ask students what the relationship is; same or opposite (positive or negative). You can see this in the top-right of the model.
From here I ask students what controls the sweating. This part depends on students making an important distinction. Many will suggest ambient temperature. So I give them an example, such as, someone who is skiing in the Pyrenees. The ambient temperature is below zero degrees Celsius, but through activity and wrapped in thick clothing they are sweating.
The same example works if students have begun with shivering rather than sweating. The goal is to make the distinction between ambient temperature as something that affects the inflow and outflow of heat*, and body temperature as part of the feedback loop of regulation.
*In my simplified model, I decided to include ambient temperature as a factor affecting heat gain, but it could also affect heat loss in more elaborate models.
With this distinction made, we can complete the feedback loop, drawing the arrow from the stock (heat in body) to the response (sweating), and again, ask students if it is a "same" or "opposite" relationship. And the first loop is complete, I'll add vasodilation later.
I ask students to follow the loop with me, using whole class call and response, something like this:
The heat in the body increases, this causes sweating to...
Sweating increases, so this causes...
Heat loss increases, so this causes...
An increase in body temperature, ultimately leads to a decrease in body temperature. Homeostasis, indicating a negative feedback loop, which I add to the model.
Now it's time to add the suggestion of shivering. I ask my students to simplify the suggestion to something that directly causes the heat production. This brings us to cell respiration rate*. And I go through the same process as above to add in this feedback loop.
*I could add another separate loop between the heat in the body and cell respiration rate, but for this class I decided not to add this extra distinction to the model.
Now I want to include responses that students may know less about, and so I draw a diagram of the skin next to the model. And I discuss with the students the thermoregulatory responses of hair erection in mammals, and vasodilation and constriction.
Having discussed this in concrete (bodily) terms, I ask students to have a go at adding the responses to the model. They make some predictions, I walk the room to see them, and then I bring the class back to show them.
The model is now complete, and I give students some time to self-explain. This involves explaining a concept to yourself, as if to someone else, in your head. And I address any questions students have.
From here, it's time to practice *thinking with* the model through "What if?" questions and encouraging students to answer according to my published taxonomy of understanding.
Here's a couple of "What if?" questions I've asked before:
What if a person suffered a condition that caused permanent vasodilation?
What if a person could only sweat half as much as a normal person?
Another benefit of building system dynamics models is that there is no correct model. Depending on what journey your students have been on, additional factors could be added, or some taken away. I teach this at the beginning of my biology GCSE course, others may teach it later.
Part of system modelling is the circular conversation between what makes sense internally (with what we think, and thus what our students have already studied) and externally (what matches phenomena). "The map is not the territory" (Alfred Korzybski), but if it is sufficiently similar, it can be useful to think with. This is #SystemsTeaching.
My books: Difference Maker | Biology Made Real, or my other posts.
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