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.
An impulse begins when a neuron is stimulated by another neuron or by a stimulus in the environment. The cell membranes begin to change the flow of ions and a reversal of charges, the action potential, results. An impulse that changes one neuron, changes the next.ppropriate responses are carried out by effectors (a muscle or gland). The Neuron. The neuron, a nerve cell, is the functional unit of the nervous system that carries the impulse (the message) to the appropriate part of the nervous system or interprets the impulse and allows a response.