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?

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

   • Negative: the fall is harmful, so the loop is called negative
   • Positive: raising a low level helps the body, so the loop is positive
   • Positive: the response raises the level, and negative loops lower a level
   • Negative: the response reverses the fall, even though the level goes up
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: each step helps the body, and helpful loops are positive
   • Positive: thrombin pushes the change further until an end point
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?

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

   not to scale. Response: not shown. Luz reads a model of a long hot day: body fluid volume is low and ADH is released. What do the kidneys do?

   • They detect the low volume and report it to the brain
   • They release more water, so more water is lost
   • They make ADH, so the pituitary takes back more water
   • They take back more water, so less water is lost
7. 7.

   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
   • Sweat is higher at minute 40, so the response is still growing
   • Temperature is back at exactly 37 °C at minute 40
8. 8.

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

   • It returns to exactly 88 mg/dL and holds there from 90 minutes on
   • It peaks at 60 minutes, then falls below 70 mg/dL
   • 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

9. Read this first

   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.

10. 9.

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

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

11. Use this

    Investigation card (model data). Question: does room temperature change skin blood flow? Changed: room temperature, 20 °C or 30 °C. Measured: skin blood flow in relative units. Kept the same: the clothing, the time in the room and the activity. Results table: Room temperature (°C) | Skin blood flow (relative units): 20 | 3; 30 | 7.

12. 10.

    Zee's class reads a card about warm and cool rooms. What was measured in the investigation?

    • Skin blood flow, in relative units
    • The time spent in the room
    • The clothing worn in the room
    • The room temperature, 20 °C or 30 °C