why do our muscles shake when electricity touches us but not when light touches us. If it isnt energy that makes our muscles shake what is it?
In: Physics
First of all, the light does not reach your muscles, it just reaches your skin. So it cannot have any direct effect on the muscles anyway.
But more importantly, muscles cannot just convert any sort of energy into movement, just like a diesel engine can only use diesel and not steam or wind or electricity. The energy source for muscles is a specific chemical “fuel” in your body called ATP, muscles can only use that and nothing else.
However, while the ATP is the energy source, your brain has to control the muscles somehow, and it does that – simplifying here – by sending electric impulses along your nerves. If you touch an electric cable, the electricity will cause havoc with this communications system – your muscles believe that they’re given random, frantic orders, and act accordingly.
So, in short – muscle spasm don’t happen because of too much energy, but because they recieve random orders.
Your body uses electrochemical signals to tell the muscles what to do. Your brain commands the muscle by sending it a weak electrical signal.
When you get electrocuted the current from the power supply overwhelms whatever signals your brain is trying to send and the muscles will often seize up in response.
Light is a different kind of energy, and most of your tissues aren’t very responsive to it.
Animal cells don’t have any machinery that can convert light to any usable form, unlike “electricity” (in the form of action potentials).
It’s like asking why solar panels don’t generate an electric current when you shake them. Mechanical energy and electromagnetic radiation might both be forms of energy, but solar panels are only built to be able to convert one of them to electricity.
Our body uses electricity to convey nerve signals to the muscles, so even electricity from outside the body such as in EMS causes them to flex. It’s not as precise as our brain though, so the muscles don’t always make coherent movements, just random muscles flexing on and off causing a twitching motion.
Our nervous system works on electricity too. When we want to raise an arm, for example, an electrical signal goes through our nerves and makes the required muscles contract when it reaches them. So when some external electrical current touches our muscles, it’s no different to them than the normal nerve signal.
I think there’s something fundamental here that needs to be cleared up first. When you get electrocuted, the electric current isn’t *powering* your muscle cells. It’s interfering with (overwriting, in a way) the electrical signals that are normally transmitted between the brain and your muscles.
Whether you’re getting electrocuted or not, muscles are only ever powered by chemicals stored in the cell (adenosine triposphate, ATP). Neither light nor electricity can provide energy to a cell.
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