The ways in which the words can be meaningfully combined is defined by the language's syntax and grammar. The actual meaning of words and combinations of words is defined by the language's semantics.
A nerve impulse is an electrical signal that travels along an axon. There is an electrical difference between the inside of the axon and its surroundings, like a tiny battery. When the nerve is activated, there is a sudden change in the voltage across the wall of the axon, caused by the movement of ions in and out of the neuron.
Nerve Impulse Conduction. A nerve impulse begins conduction as electrical impulses, initiated by the brain, travel down through nervous system cells. The electricity causes a change in polarity by opening channels to move positive sodium or potassium ions in or out. Positive molecules are stored in membranes guarded by gated channels.