Nerves use electricity to send signals. Where is this electricity created.?

To be as simple as possible, basically what happens is that the nerve cells pump potassium ions (positive charge) out of the cell across a membrane. This sets up what is called an action potential. Then, when it needs to send an electrical signal, it allows the ions to suddenly flood back through the membrane via channels the cell opens up in the membrane. The sudden movement of charge induces the electrical signal.

An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma. Axons are in effect the primary transmission lines of the nervous system, and as bundles they help make up nerves. Individual axons are microscopic in diameter - typically about one micrometre across - but may extend to macroscopic lengths. The longest axons in the human body, for example, are those of the sciatic nerve, which run from the base of the spine to the big toe of each foot. These single-cell fibers may extend a meter or even longer.

In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. Ligand-induced changes in the behavior of receptor proteins result in physiological changes that constitute the biological actions of the ligands.

It is generated in many/most cells by the flow of sodium ions and chlorine ions across the cell membrane. When a cell "fires" the membrane becomes selectively permeable to sodium ions that rush in causing a net electrical charge. After firing, the cell then pumps the sodium back out of the cell. NEATO!!

This is why salt (sodium chloride) is so essential to life. Wonder if it is just a coincidence that our bodies function thanks to seawater?

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Electricity is energy. Energy can not be created nor destroyed.