A new medicine is injected into the fluid that surrounds the spinal cord of a laboratory rat. The medicine is designed to remain within the central nervous system. Thirty minutes after the injection, tissue samples from four structures are tested.
| Structure | Concentration of medicine in the sample / mg per kg |
|---|---|
| brain | 6.2 |
| spinal cord | 5.7 |
| sensory nerve | 0.0 |
| motor nerve | 0.0 |
Explain whether the results support the claim that the medicine has remained within the central nervous system.
111 exam-style questions on Edexcel GCSE Biology 2.3 The nervous system and brain, covering 2.3.1 Structures and functions of the brain, 2.3.2 Imaging brain function with scanning, 2.3.3 Limitations in treating nervous system damage, 2.3.4 Neurones and impulse transmission, and 2.3.5 Structure and function of a reflex arc. Each one has a worked solution and a mark scheme showing where the marks go.