Homeostasis: how the body keeps things steady

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Use this

   Feedback loop (model, not to scale) for body temperature, set point about 37 °C. Stimulus: body temperature rises above the set point. Sensor: temperature sensors. Control center: the hypothalamus, the brain's temperature control center. Effector: skin blood vessels and sweat glands. Response: heat is lost and body temperature falls toward the set point.

2. 1.

   Ari reads the loop for body temperature. In a feedback loop, what does the sensor do?

   • It is the change that starts the loop
   • It carries out the response that brings the level back
   • It compares the value with the set point and orders a response
   • It detects the change and reports it to the control center
3. 2.

   Bo reads a loop with boxes W, X, Y and Z. Which box is the effector, the part that makes the response?

   • Box Y, the hypothalamus, which compares and decides
   • Box Z, the rise in body temperature that starts the loop
   • Box X, the skin blood vessels and sweat glands
   • Box W, the temperature sensors that detect the rise

4. Use this

   Feedback loop (model, not to scale) for a level X. A change in X is the stimulus. A sensor detects the change, a control center decides, and an effector responds.

5. 3.

   Esme reads a model loop for a level X. In plain words, what does negative feedback do?

   • It reverses a change and moves the level back toward the set point
   • It stops the sensor from detecting the change
   • It is a harmful process that the body works to avoid
   • It pushes the change further away from the set point
6. 4.

   model, not to scale. Jun reads the loop for a cold day. What goes in the blank effector box?

   • Temperature sensors that detect the fall in temperature
   • Skin blood vessels that widen and sweat glands that release sweat
   • The hypothalamus, which compares the value with the set point
   • Skin blood vessels that narrow and muscles that shiver

7. Use this

   Two cases (model, not to scale), each starting when body temperature rises above about 37 °C. Case 1: sweat is released, and body temperature falls back toward 37 °C. Case 2: muscles make extra heat, and body temperature rises more.

8. 5.

   Milo compares two cases for a rise in body temperature. Which case is negative feedback?

   • Neither case, because the temperature changes in both cases
   • Case 2, because negative means the change harms the body
   • Case 2, because a negative loop makes the change grow bigger
   • Case 1, because the response reverses the rise

9. Use this

   Two cases (model, not to scale). Case 1: after a meal the glucose level rises above its normal range of about 70 to 100 mg/dL, and the pancreas releases a hormone that lowers it. Case 2: between meals the glucose level falls below that range, and the pancreas releases a different hormone.

10. 6.

    Noah reads two cases about the glucose level. Which hormone is released in Case 2?

    • Glucagon, which raises the glucose level
    • ADH, which brings the glucose level up
    • Insulin, which brings the glucose level up
    • Insulin, which brings the glucose level down
11. 7.

    Pia compares two model loops for a level X. Which case is positive feedback?

    • Both cases, because each one starts with a rise in X
    • Case 1, because the response brings the level back to normal
    • Neither case, because X changes in both loops
    • Case 2, because the response pushes the change further
12. 8.

    Ren reads a graph of body temperature at rest. Which statement matches the graph?

    • It wobbles a little above and below the set point of about 37 °C
    • It rises steadily across the eight hours of the graph
    • It falls below 36 °C at hour 4 and stays there
    • It holds at exactly 37 °C throughout the eight hours
13. 9.

    Tala reads a graph of the glucose level between meals. Which statement matches the graph?

    • It falls below 70 mg/dL at hour 3
    • It rises above 100 mg/dL by hour 4
    • It wobbles a little, staying inside the normal range
    • It holds at exactly 90 mg/dL the whole time
14. 10.

    Zee reads the ADH loop. Which part is the effector, the part that carries out the response?

    • The kidneys, which take back water
    • The low body fluid volume that starts the loop
    • The hypothalamus, which makes ADH
    • The posterior pituitary, which releases ADH