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.
Biology Glossary search by EverythingBio.com. AKA: nerve impulse. The signal that travels along the length of a nerve fiber and ends in the release of neurotransmitters. Nerve impulses are the means by which information is transmitted along the neuron and throughout the nervous system.