Residual nerve reaction

[Cecil]

I was watching some show on TV, and they euthanized a rat and tossed it to a snake. After biting it, the snake left it to die. The rat started kicking violently at the air, and then the narrator explained that it was already dead and the kicking was just "residual nerve reaction".

What is this? I can't find any reference to it on google, and it doesn't seem possible to me that nerves could still fire after an animal is dead. Isn't that the definition of death; nerve activity has ceased?

[Brown]

All I have to say is that my high school biology teacher cut the head off a frog, then dropped the frog to the table, and the frog jumped with a coordinated action as if it were alive.

[Dr. Imago]

Depends on how long something has been dead and what level of innervation is severed.

In Cecil's example, there may still be sufficient ability for anaerobic metabolism available to allow muscles to move. If an efferent nerve or the neuromuscular junction is somehow stimulated below the cord, then the muscle will move.

In Brown's example, called "pithing", all upper motor neuron function is destroyed. However, the lower motor neuron (e.g. cord level) function as well as the autonomic centers are preserved. This is done to be able to humanely examine the frog's innards still functioning. The jumping you witnessed may be a lower, brainstem type reflexive behavior that the frog could no longer suppress with his upper cortical function.

I'm also not aware of a specific term "residual nerve reaction", but this may simply be from ignorance. I think it could equally, and perhaps more exactingly, be called "post-mortem lower motor neuron action".

-TT

(P.S. Nice coincidence that your name is "Cecil" as this is also the name a very famous and widely used medical text.)

[Deetee]

Headless chickens spring to mind.

Some creatures have evolved a mechanism for body parts to continue to move after "removal", such as lizards. When attacked, they drop their tails off, and these continue to writhe around, nicely distracting the predator's attentions, while lizzie escapes to grow a new tail and live and fight another day.

This is different from the neuronal discharges that make dead things jerk, however in the manner TT has explained'.