Maintaining Balance: The Homeostasis of Heart Rate - Student Handout

NGSS Alignment: HS-LS1-3

Performance Expectation: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

Part 1: Engage (Anchoring Phenomenon)

Consider a professional athlete competing in a marathon.

  1. Prediction: What happens to their heart rate as they transition from standing at the starting line to sprinting toward the finish?
  2. Prediction: What happens to their skin color and sweat production if the race is held in a 35°C desert?
  3. The Question: How does the body “know” when to increase heart rate or start sweating?

Part 2: Explore (Clinical Investigation)

Open the Homeostasis Investigation Simulation. You will plan and conduct an investigation to provide evidence of feedback mechanisms.

Experimental Data Table:

| Condition | Sim Time (min) | Env Temp (°C) | Activity | Heart Rate (bpm) | Core Temp (°C) | Observations | | :— | :— | :— | :— | :— | :— | :— | | Baseline | 5 | 22 | Resting | | | | | Max Exercise | 20 | 22 | Running | | | | | Desert Heat | 10 | 45 | Resting | | | | | Extreme Combined | 10 | 45 | Running | | | |

Part 3: Explain (Sensemaking)

  1. The Heart Rate Loop: Why did the heart rate increase during the “Running” phase?
  2. The Temperature Loop: How did the responses you observed help lower the core temperature?
  3. Negative Feedback: Explain how your data provides evidence of negative feedback.
  4. Evidence-Based Claim: Use data from your table to support the claim that the body maintains a “set point” for core temperature.

Part 4: Elaborate/Evaluate (Refining the Investigation)

  1. Accuracy: What tools would you need in a real lab to achieve the precision seen in this simulation?
  2. Refinement: How would you change your procedure to test the impact of “Clothing Insulation”?
  3. Argumentation: Argue for or against the claim: “Heart rate only increases when you exercise.” Use evidence from the simulation.

Part 5: Summary Model

Describe the components of a feedback loop for temperature regulation: