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.
What is a nerve impulse? A nerve impulse, or an action potential, is a series of electrical responses that occur in the cell. (Fig. 2) With the appropriate stimulation, the voltage in the dendrite of the neuron will become somewhat less negative.This change in the membrane potential, called depolarization, will cause the voltage-gated sodium channels to open. Sodium ions will rush in, resulting in a rapid change in the charge.At the peak of the action potential, that area of the neuron is about 40 mV positive. As the voltage becomes positive, the sodium channels close, or inactivate, and the voltage-gated potassium channels open.These potassium channels let potassium ions rush out of the cell, causing the voltage to become negative again.) With the appropriate stimulation, the voltage in the dendrite of the neuron will become somewhat less negative. This change in the membrane potential, called depolarization, will cause the voltage-gated sodium channels to open. Sodium ions will rush in, resulting in a rapid change in the charge.