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 impulses are a way of coding information, in a similar way to FM radio, allowing information to be transmitted both quickly and accurately. Each impulse is the same size so it is the frequency that carries information about the intensity of the signal. For example, as you turn up the dimmer switch on your bedroom light, the size of the nerve impulses from your eye stays the same but the rate at which they are generated increases. Back to top.