An impulse will be started in the hillock if the neural currents in the dendrites and soma are favorable. If they are, an impulse is triggered and it travels down the axon to the terminals where it influences other neurons by way of the synapses on them. To get a sense of what is to come in later parts of this lecture, let's introduce a very important general concept right now, even though it won't make a lot of sense to you at this time. The function of the soma and dendrites is to create information and this is what is being done when the neural currents from all over the soma and dendrites are summated at the axon hillock. The function of the axon is to carry those nerve impulses to other neurons, elsewhere.
Information is handled in the nervous system in the form of a code made of nerve impulses.
For example, the sight of a friend's face will create one pattern of nerve impulses in the optic nerve whereas the sight of a house would be a different code. Green is represented by one pattern, red by another. Every single stimulus that you can perceive is represented by its own, unique code. If two different stimuli accidentally produce the same pattern of nerve impulses in the brain, they will appear to be exactly the same to you. You won't be able to tell them apart.