Homeostasis: how the body keeps things steady

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   After a bike ride, Ari's body temperature rises and sweat is released, and the temperature falls back. Is this negative or positive feedback?

   • Positive: the temperature rises first, so the loop is positive
   • Negative: the response lowers the temperature back toward the set point
   • Negative: the loop is harmful, which is what negative means
   • Positive: the response helps the body, and helpful responses are positive
2. 2.

   Bo reads a model in which a person's glucose level falls between meals and glucagon raises it. Is this negative or positive feedback?

   • Positive: the response raises the level, and negative loops lower a level
   • Positive: raising a low level helps the body, so the loop is positive
   • Negative: the response reverses the fall, even though the level goes up
   • Negative: the fall is harmful, so the loop is called negative
3. 3.

   Clotting boxes (model, not to scale), starting when a small blood vessel wall is broken. Esme reads the clotting boxes. Thrombin activates earlier factors, so more thrombin forms until a clot is complete. Is this negative or positive feedback?

   • Negative: the finished clot reverses the process, so it is negative
   • Negative: the response makes the process bigger, as negative loops do
   • Positive: thrombin pushes the change further until an end point
   • Positive: each step helps the body, and helpful loops are positive
4. 4.

   After a game, Jun's body temperature is 38.2 °C. The control center orders the effectors to respond. What do the effectors do?

   • Skin blood flow falls and the muscles shiver
   • The muscles make extra heat, so the temperature rises further
   • The temperature sensors release sweat onto the skin
   • Skin blood flow rises and sweat is released
5. 5.

   Response: not shown. Kira reads a model: during a long walk, a person's glucose level falls to 68 mg/dL. What follows, and what happens to the level?

   • Glucagon is released, and the glucose level falls further
   • No hormone is released, since negative feedback lowers a level
   • Insulin is released, and the glucose level rises toward the range
   • Glucagon is released, and the level rises toward the range
6. 6.

   The run lasts from minute 0 to minute 20, and the set point is about 37 °C. Milo compares minute 20 with minute 40 on the card. Which statement does the card support?

   • Temperature is lower at minute 40, but skin blood flow is higher
   • Temperature, skin blood flow and sweat are lower at minute 40
   • Temperature is back at exactly 37 °C at minute 40
   • Sweat is higher at minute 40, so the response is still growing
7. 7.

   A meal is eaten just after minute 0, and the normal range is about 70 to 100 mg/dL. Noah compares insulin and glucagon at minute 30 on the card. Which statement matches the card?

   • Insulin is higher than glucagon, and the glucose level is below the range
   • The two hormones are equal, so the glucose level is steady
   • Insulin is higher than glucagon, and the glucose level is above the range
   • Glucagon is higher than insulin, and the glucose level is above the range
8. 8.

   Pia reads a graph of the glucose level after a meal. Which statement matches the graph?

   • It peaks above the range at 30 minutes, then is back inside it by 90
   • It keeps rising after the peak, so the response pushes the level further
   • It peaks at 60 minutes, then falls below 70 mg/dL
   • It returns to exactly 88 mg/dL and holds there from 90 minutes on

9. Read this first

   Use this

   Investigation card (model data). Question: does running time change body temperature? Changed: minutes of running on a track. Measured: body temperature in °C. Kept the same: the pace, the track and the thermometer. Results table: Running time (minutes) | Body temperature (°C): 0 | 37.0; 10 | 37.6; 20 | 38.0.

10. 9.

    Ren's class reads an investigation card about exercise. What did the researchers change on purpose?

    • The body temperature in degrees Celsius
    • The type of thermometer that was used
    • The number of minutes spent running
    • The pace of the runner on the track

11. Use this

    Investigation card (model data). Question: does the kind of snack change how high the glucose level rises? Changed: the snack, an apple or a slice of bread. Measured: glucose level 30 minutes after eating, in mg/dL. Kept the same: the time of day and the rest before eating. Results table: Snack | Glucose level at 30 minutes (mg/dL): apple | 104; bread | 118.

12. 10.

    Tala's class reads a card about two snacks. What was kept the same so the test is fair?

    • The time of day and the rest before eating
    • The amount of insulin the pancreas released
    • The snack, an apple or a slice of bread
    • The glucose level 30 minutes after eating