David Stock asked:
When a person has spinal damage that leads to paralysis and the loss of feeling, is the loss of feeling that they get the reason for the paralysis (i.e. the brain canít feel your limbs and canít move it) or is it the other way around?
It can be both because the spinal cord isnít just a one-way street. Itís got information coming out of the brain, down to what we call motor neurons, the motor nerves that supply your muscles. At the same time informationís coming in from your body, going up the spinal column, into your brain, telling your brain where your body is in space, how fast different muscle groups are moving and where they are and whether the movement youíre just made has been completed. So if youíve damaged the spinal cord you can damage just the sensory fibres and that means you canít feel your body but you could potentially still move. You can damage just the motor fibres which means although you can feel your body you canít make any movements. More usually itís impossible to be that discrete when you make a lesion in the spinal cord. For example, people dive into the swimming pool where itís too shallow and they impact on their neck. They break their neck, it severs the spinal cord and it disjoints all of the fibres coming up from the body: telling your brain what your body is doing/what it feels like, as well as the fibres coming out of your brain that tell you muscles to move. This means you canít feel your body nor make it move, so itís very unpleasant.