Electricity travels the path of least resistance. Some parts of the body are surprisingly good insulators- since are fantastic conductors. In a healthy human body- the extremely low current created by the brain can’t jump the insulator bits- and stay in the nervous system pathways. Several neurological conditions exist where this isn’t the case.
Electricity flows when charged particles move from areas of high concentration to low concentration. Once all those particles have moved, the flow stops. The fluids inside and outside our cells have different concentrations of charged partials. This has the effect of causing an electrical charge between the inside and outside of the cell. In order for electricity to flow, the ions need a way to flow in and out of the cell. However, there is a cell membrane in the way that prevents the ions from flowing between the two. It does happen though. This happens in a controlled manner to let neurons fire and ions essentially leak in and out of the cell during other biological processes. Our cells have molecular pumps and valves to move ions around to create or maintain charges.
Because our bodies aren’t just bags of water, and the electrical impulses in our bodies are not the same as electricity that we’re familiar with. Nerve impulses travel through the nervous system, which is made of cells that are made to conduct signals. They’re insulated. Also, our nerve impulses aren’t electrons moving, like the electricity we use. They’re voltage differences caused by different concentrations of ions. It’s a chemical process.
The nerves are wrapped in a substance called myelin, which insulates them (not letting the electricity go somewhere else). Each neuronal impulse can reach -80 mV, so it’s not that much energy to cause “short circuit”.
Although, there are part of the nervous system that are demyelinated, but, you know, lipids (fat) are good insulators, and most of the cell membranes are made of lipids.
Because said impulses travel through the nervous system, which is designed to do so. It’s like, international communications are done through giant cables that run in the oceans and they don’t short out. The nerves have membranes that keep things not part of the nerves out, just like the cables waterproof insulation does.
Plus the electrical impulses are chemical rather than electrons rushing around like we use for power generators.
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