Do you know your brain produces electric charges, I was seeing a documentary where a special device was used to visualize activity inside single nerve cells in the brain of tiny fishes, and it was fun to look but do you know that just similar to how charges where seen with thoughts in the brain of the fish, human brains work just like that.
Everything we think of as well as actions we take come from neurons interacting with one another. While you might want to regard to your brain as small, you should know that it isn't as it has over 86 billion neurons with each exchanging neural signals with one another. From sleeping, waking, standing, talking, the love, pain, humor, sadness, memory, dream, and every other stimulus and activity in the body depends on electrical communication from the brain.
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Our bodies are large compared to that of our unicellular neighbors like bacteria that do not require much to send messages to themselves, they just use chemicals to send messages which reaches other parts of their body via diffusion but as multicellular organisms having larger body, we do not use chemicals alone. I use the word alone because we use chemicals to send information via hormones but this is very slow to transmit and it is in this case that we use electrical signals to transmit information.
For instance, there was a day I was going to the market, and I got pricked by a nail which was very painful. I am not talking about the pain itself now but the speed at which the pain was felt. It is no doubt that if I were to depend on chemicals to send this signal, it was going to take a while but with electric signalling, it reaches the brain very fast. When incidents like the nail pricking happens, nerve cells send messages to the brain very fast and this is done easily since synapses are close to one another thereby making it possible to send information.
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This transfer of information is done with using electricity which was first identified in Italy with a dead frog legs thanks to Luigi Galvani who had an idea that electricity was alive as he wanted to understand why some fish gave off electric shock or why fossilized tree sap when rubbed together attracted stuffs? He was able to observe the frog legs twitching as a result of static electricity and lightening and he noticed that it wasn't psychic fluids or magic. He went to to further observe the frog legs and he noticed that the leg twitched when a couple of metals was used to touch the legs. He then said that we were filled with electricity which he referred to as Animal Electricity.
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There are different types of neurons in the body, but they are all built the same way. They are made up of the cell body, dendrite (which is used to receive signal from another nerve), Axon which is the wire, and the synapse which is used to pass the neural signal. As we discuss neurons, we cannot forget Action potentials which are our living electricity. In a neuron's axon, charged ions are constantly pumped in and out of the axon, pumping sodium ion out of the cell and potassium ion into the cell as the potassium - sodium gradient is being balanced in and out of the cell.
So when you wonder why your hands move just as you think it, it is because the information travels very fast through the nervous system and reaches the destination instantaneously. In the case of he Nail pricking, the nervous system received two messages with one being faster than the other and follow two different part. The first is touch and the second is pain, with the first traveling faster than the second but I can still testify that the electric charge used in sending the message is still faster than using hormones or chemical messages.
Reference
https://www.janelia.org/sites/default/files/Library/Ahrens%202013.SOM__4.pdf
https://epub.uni-regensburg.de/27126/1/schmidgen.pdf
https://www.sciencedirect.com/science/article/abs/pii/S0160932702014667?via%3Dihub
https://core.ac.uk/download/pdf/215692177.pdf
https://jamanetwork.com/journals/jama/article-abstract/289164
https://www.jstor.org/stable/226359
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4241473/
https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology
https://www.medicalnewstoday.com/articles/320289
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6826821/