Fig. 1 shows a simplified spinal cord and two pathways from the right foot. A climber fell and damaged the right side of their spinal cord at the level mark...
Question 1 Report
Fig. 1 shows a simplified spinal cord and two pathways from the right foot. A climber fell and damaged the right side of their spinal cord at the level marked D. Before treatment, the climber could feel pressure on the right foot but could not move the right foot voluntarily. The doctor tested reflexes by tapping below the knee and tested sensation using a soft brush. The brain, spinal cord and neurones form the central and peripheral nervous systems. The figure is not drawn to scale. It shows that sensory and motor information can travel in different directions within the nervous system.
(a) What type of neurone is X? [1]
(b) What type of neurone is Y? [1]
(c) Describe why the climber can still feel pressure on the right foot. [2]
(d) Explain why the climber cannot make a voluntary movement of the right foot. [3]
(e) Give two reasons why a knee reflex may still occur even though the spinal cord is damaged. [2]
(f) Complete the pathway: receptor in foot → sensory neurone → ............ → motor neurone → muscle. [1]
Answer Details
Spinal cord pathways
- X is a sensory neurone. [1]
- Y is a motor neurone. [1]
- The climber can still feel pressure because sensory impulses from the foot can travel to the brain. The sensory pathway has not been damaged or cut at D. [2]
- Voluntary movement is controlled by the brain. Motor impulses cannot pass through damaged region D, so they do not reach the foot muscle and the muscle cannot contract voluntarily. [3]
- A knee reflex may still occur because reflexes can be coordinated in the spinal cord and do not need conscious input from the brain. Also, the neurones involved may lie below, or not pass across, the damaged region. Any two points are required. [2]
- The missing part is a relay neurone, or the spinal cord. The complete pathway is receptor in foot → sensory neurone → relay neurone → motor neurone → muscle. [1]
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