How can I take a signal from one part of the body say the brain and transmit to another part of the body say the toe without using nerves or any external device? Especially say there is a spinal cord injury resulting in nerve death in just a small part but still enough to block signals. I dont want to use electrodes or wires or wireless transmission. Just want to use what the body has.
There isn't any way once you've excluded everything you've excluded. There might be spinal cord regeneration, but that would use nerves. The human body has no other innate mechanism available with sufficient bandwidth or responsiveness, and you would seem to have ruled out technological means.
There is good reason why people with sufficiently severe spinal cord injuries are considered permanently disabled.
There's plenty of ways, though none of them are a very good match for what nerves do:
- Chemical signals - there are many chemical signals which travel through the blood stream. Adrenaline is one excellent example.
- Muscular waves - You could use your muscles to set up a wave of motion, which could be picked up by the sensory nerves on the toe.
- Touch - Don't forget the obvious. If you want to send a signal from a finger to a toe, you can always use the finger to touch the toe.
Endocrine System - Effective But Slow And Costly
The endocrine system includes the glands and hormones. This system is effectively in work in people with severe nerve injury too. But using this system, you can only signal the parts of body which have specialised receptors for detecting those chemicals (hormones) in the blood. You cannot use it to individually signal every part of the body.
Also, hormones take time to build. If you want to play football using this method, it will not work. Also, releasing hormones directly into the bloodstream also means that the signal will reach the target after some time and will stay in the bloodstream for sometime. So while you can use it to signal primary information such as hunger, absorption or release of some chemical etc, you cannot use it for quick, precisely controlled movements.