A person's finger is pinched by a closing drawer. The table shows the time of events after the finger is pinched.
| Event | Time after the finger is pinched in ms |
|---|---|
| impulse reaches the spinal cord | 22 |
| electrical activity begins in an arm muscle | 38 |
| impulse reaches the cerebral hemispheres | 54 |
| conscious awareness of pain begins | 68 |
Explain, using the information in the table, why electrical activity begins in the arm muscle before the person becomes consciously aware of pain. Explain how the time at which the muscle becomes active would change if the reflex pathway contained one additional synapse.
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.