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 detects the change and reports it to the control center
   • It compares the value with the set point and orders a response
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 stops the sensor from detecting the change
   • It reverses a change and moves the level back toward the set point
   • 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
   • The hypothalamus, which compares the value with the set point
   • Skin blood vessels that widen and sweat glands that release sweat
   • Skin blood vessels that narrow and muscles that shiver
7. 5.

   “model, not to scale” After a meal the glucose level rises. Kira reads the loop. What goes in the blank control center box?

   • The pancreas, which releases the hormone glucagon
   • The kidneys, which release the hormone ADH
   • The pancreas, which releases the hormone insulin
   • The liver, which releases the hormone insulin

8. Use this

   Clotting boxes (model, not to scale), starting when a small blood vessel wall is broken. The blank box activates more early clotting factors, and it turns fibrinogen into fibrin to make a clot.

9. 6.

   Luz reads the clotting boxes. What goes in the blank box?

   • Insulin, which also activates the earlier factors
   • Fibrin, which also activates the earlier factors
   • Fibrinogen, which also activates the earlier factors
   • Thrombin, which also activates the earlier factors

10. 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.

11. 7.

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

    • Case 2, because a negative loop makes the change grow bigger
    • Case 2, because negative means the change harms the body
    • Neither case, because the temperature changes in both cases
    • Case 1, because the response reverses the rise
12. 8.

    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 2, because the response pushes the change further
    • Neither case, because X changes in both loops
    • Case 1, because the response brings the level back to normal
13. 9.

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

    • It rises steadily across the eight hours of the graph
    • It holds at exactly 37 °C throughout the eight hours
    • It falls below 36 °C at hour 4 and stays there
    • It wobbles a little above and below the set point of about 37 °C
14. 10.

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

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