Researchers tested the automatic control of blood glucose concentration in a rat. The optimum blood glucose concentration was 5.0 mmol/dm³. All parts of the control system were functioning normally. At time 0, the blood glucose concentration was lowered to 3.4 mmol/dm³.
| Time in minutes | Blood glucose concentration in mmol/dm³ | Receptor output in arbitrary units | Effector activity in arbitrary units |
|---|---|---|---|
| 0 | 3.4 | 8 | 8 |
| 5 | 3.8 | 6 | 7 |
| 10 | 4.4 | 3 | 5 |
| 15 | 4.8 | 1 | 2 |
| 20 | 5.0 | 0 | 0 |
Explain how the data show that the automatic control system maintains homeostasis.
In a second test, the communication pathway from the coordination centre to the effector was blocked immediately before time 0. The blood glucose concentration was then lowered to 3.4 mmol/dm³ at time 0.
Predict how the blood glucose concentration at 20 minutes would differ from the value shown in the table. Explain your answer.
76 exam-style questions on AQA GCSE Biology 5.1 Homeostasis, covering 5.1 Homeostasis. Each one has a worked solution and a mark scheme showing where the marks go.