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.
Nervous System. STUDY. PLAY. neuron. mass of nerve cells; structural and functional unit of nervous system; specialized to react to physical and chemical changes in their surroundings; transmits info in the form of electrochemical changes (nerve impulses) to other neurons and to cells outside nervous system. nerve impulse.