Have you ever been shocked to see severed frog legs still moving? What causes this phenomenon, and how can certain body parts, like the body and legs, still “dance” without a brain or nervous system to control them?
Why do some animals still “dance” even after losing a body part?
Even when skinned and completely dismembered, frog legs are not entirely “dead.” These legs still contain life, and you can test this with a bit of salt. The sodium ions in the salt act as a stimulus, mimicking signals from the brain and nervous system, which results in a burning sensation. Because energy remains in the cells, the muscles in the frog’s legs begin to twitch in response to the stimulus, creating the phenomenon of “dancing” frog legs.
It’s not just frogs; several animals also possess this “strange” ability.
Sashimi is a traditional Japanese dish primarily made from fresh seafood. Viewers may be shocked to see chefs filleting fish that continue to thrash about. However, cephalopods are a class of mollusks that are very easy to kill, and the movements observed after preparation can be explained further.
Even after death, the human body can still experience random spasms, and limbs may continue to move for several hours due to a different mechanism than how squid tentacles operate after the body has been severed.
A fish continues to thrash around as it seemingly tries to escape after having its head and intestines removed.
So, what is the reason that tissues can still move without signals being sent and received through the brain and nervous system, or without a heartbeat? Although the brain and heart are inactive, the cells can still respond to stimuli, such as the addition of sodium.
After death, motor neurons (the nerves that facilitate movement between tissues) are activated by remaining electronic signals, which still harbor some latent cell membranes (the difference in ion concentration).
All cells are polarized, meaning there is a difference in the concentration of charged molecules, or ions, inside the cells compared to the outside. This concentration difference creates an electric charge on the cell membrane.
Frog legs “dance” after being salted, as posted by Thearchipelagos on YouTube.
When not activated by the nervous system, neurons maintain the capability of the cell membrane by balancing the ions of sodium and potassium (both of which are necessary for stimulating the burning of nerve cells).
However, when neurons are activated by electronic signals, specific channels between cells open, allowing sodium ions to rush in. When the electric charge within the cell needs to balance with the environment, potassium channels also open, allowing potassium to flow out of the cell.
Eventually, the channels close, and the neurons work to restore the balance between sodium and potassium concentrations inside and outside the cell, but not before the activation of nearby channels triggers a chain reaction in the muscle.
This is the basic way neurons produce movement within a tissue.
A squid continues to move its tentacles even after the chef has sliced the body into pieces.
As previously mentioned, immediately after death, motor neurons still retain some membrane capabilities, or differences in ion responsibility, which then initiate a chain reaction along the nerve pathways causing movement.
Adding sodium, in forms such as table salt or soy sauce, significantly enhances these reactions.
