Homeostasis: how the body keeps things steady

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   A meal is eaten just after minute 0, and the normal range is about 70 to 100 mg/dL. Luz reads the meal card. At which minute does it show the strongest response to a low glucose level?

   • Minute 30: insulin is highest at 9 while the glucose level is highest at 125
   • Minute 120: glucagon is 4 and the glucose level is 85, the middle of the card
   • Minute 60: the glucose level equals the set point of 100, so no hormone acts
   • Minute 180: glucagon is highest at 7 while the glucose level is lowest at 70
2. 2.

   The run lasts from minute 0 to minute 15, and the set point is about 37 °C. Kira reads the exercise card. After minute 15, temperature, skin blood flow and sweat all fall. What does this show about the loop?

   • The response grew stronger as the temperature fell, pushing it further
   • The set point fell, so less cooling was needed
   • The stimulus shrank as the temperature fell, so the response eased
   • The loop switched off because the temperature reached exactly 37 °C
3. 3.

   Esme reads a graph of the glucose level after meal A and meal B. Which statement does the graph support?

   • Meal B raised the level higher and took longer to return inside the range
   • Meal A kept rising after 30 minutes, so the response pushed it further
   • Both lines end at exactly 90 mg/dL, so the loop holds the set point
   • Meal A took longer than meal B to return inside the range
4. 4.

   Bo edits a model of the body temperature loop: the arrow from the control center to the effectors is cut. Body temperature then rises above 37 °C. What does the model predict?

   • The temperature stays at exactly 37 °C, because the set point holds it there
   • The temperature stays above the set point, because the effectors get no order
   • The temperature falls back, because the sensors make the response themselves
   • The temperature rises faster, because the cut arrow makes the loop positive
5. 5.

   In a model, Jun changes the loop so that, after a meal, the pancreas releases glucagon instead of insulin. What happens to the glucose level?

   • It falls, because negative feedback lowers a level
   • It stays the same, because glucagon has no effect after a meal
   • It rises further, because glucagon raises the glucose level
   • It stays inside the range, because the loop still reverses the change

6. Read this first

   Use this

   Notebook (model data), 4 rows. Columns: line, what it says. 1, Temperature sensors detect a rise in body temperature. 2, The control center compares the value with the set point. 3, The sensors then make the response, such as sweating. 4, The response brings body temperature back toward the set point.

7. 6.

   Ari reviews a classmate's notebook on the body temperature loop. Exactly one line is wrong. Which line, and why?

   • Line 2, because the sensors compare the value with the set point
   • Line 3, because the effectors, not the sensors, make the response
   • Line 4, because the response makes the temperature rise more
   • Line 1, because the control center detects a rise in temperature

8. Use this

   Notebook (model data), 4 rows. Columns: line, what it says. 1, After a meal the glucose level rises. 2, The pancreas releases insulin. 3, Insulin raises the glucose level so cells have fuel. 4, Between meals, glucagon is released when the level falls.

9. 7.

   Tala reviews a classmate's notebook on the glucose level. Exactly one line is wrong. Which line, and why?

   • Line 1, because the glucose level falls after a meal
   • Line 4, because a negative loop cannot raise a level
   • Line 3, because insulin lowers the glucose level
   • Line 2, because the pancreas releases glucagon after a meal

10. Use this

    Notebook (model data), 4 rows. Columns: line, what it says. 1, In a negative loop, the response reverses the change. 2, In a positive loop, the response pushes the change further. 3, A positive loop in the body runs until it reaches an end point. 4, Positive feedback is the usual kind in the body, and negative is rare.

11. 8.

    Pia reviews a classmate's notebook on kinds of feedback. Exactly one line is wrong. Which line, and why?

    • Line 2, because a positive loop reverses the change that started it
    • Line 3, because a positive loop has no end point
    • Line 1, because a negative loop lowers a level instead of reversing a change
    • Line 4, because negative feedback is the usual kind in the body

12. Use this

    Two loops (model, not to scale) for the glucose level, normal range about 70 to 100 mg/dL. Loop 1: the level rises above the range, insulin is released, and the level falls. Loop 2: the level falls below the range, glucagon is released, and the level rises.

13. 9.

    Tala claims the glucose system is not negative feedback, because glucagon raises the level. Is the claim sound?

    • No: each loop reverses a change, so raising a low level is also negative feedback
    • No: raising a low level helps the body, so Loop 2 is positive feedback
    • Yes: negative feedback lowers a level, and glucagon raises it
    • Yes: the glucagon loop helps the body, and negative feedback is the harmful kind

14. Use this

    Two loops (model, not to scale). ADH loop: body fluid volume is low, ADH reaches the kidneys, and they take back more water. Glucose loop: the glucose level rises after a meal, insulin is released, and liver, muscle and fat cells take up glucose.

15. 10.

    Zee compares the ADH loop with the glucose loop after a meal. What do the two loops have in common?

    • Each has a response that pushes the change further until an end point
    • Each has a response that reverses the change that started it
    • In each, the sensor is the part that carries out the response
    • In each, the controlled value stays at exactly its set point