This involves a cat, which has made me curious about he mammalian nervous system.
Disclaimer: not looking for medical or veterinary advice. This is not my cat. It’s a friend’s cat. It has gone to the vet and is scheduled to go see some kind of cat neurologist and/or get an MRI (yes, a cat). I’m just curious about how the nervous system works, or in this case, doesn’t work.
So this indoor-only cat was fine at night, but in the morning had lost the use of its hind legs (bilateral paralysis, both legs are affected, no trauma, cat was snoozing at the foot of the bed all night). So cat went to vet, vet was testing cat and put a clamp on the cat’s toe to see if the cat felt it. At first the cat did not appear to feel it, and seemed to have no awareness of the clamp on its toe at all. The vet started talking. About 45-60 seconds later, the cat started making pissed off “Ouch! Ouch! What’s on my toe???” yelps of angry pinched-toe noises. Clamp was removed.
So that’s what made me curious. I can understand no sensation, or a dull/muted sensation, but how does the nervous system work/not work for such a delayed response to stimuli? I have only a very basic idea of how the nervous system works. Doesn’t the nervous system work on electrical impulses? Why would it “slow down”? Or is it that the impulses are moving along just fine, but that the brain is taking longer to sort out the raw data of the sensory message: “ouch, there’s a clamp on my toe”?
Complex subject, but in simple terms the nervous system doesn’t work on electrical signals. Most of the distance is covered electrically, but there are chemical repeater stations between individual nerves (actually neurons) that serve to modulate the signal and make sure it’s going in the right direction. If a nerve signal is beings slowed down, that’s where it’s happening, in those repeaters. Of course a chemical reaction can run at any speed at all depending on the reactants available, the temperature and so forth. You can prove this yourself by kicking your toe on a cold morning. You won’t feel the signal for almost a full second after the damage, but when it does get there it hurts far too much for far too long because the signals that are supposed to moderate it aren;t able to flow back fast enough either.
In the case of the clamp there were probably different pain receptors at play. The fast receptors that are supposed to feel damage obviously weren’t working. However the body also had other receptors that detect swelling, lack of oxygen and so forth that also trigger a pain response. So after the clamp had been on for a while the tissue started to go anoxic and swell, much as when you put a rubber band on your finger. The cat could feel that perfectly well even if the more superficial sensors weren’t working.