What neurons do
Neurons carry information in two directions, and the whole nervous system is those two journeys repeated.
Towards the centre
Transmitting information obtained by receptors — the eye, the ear, the nose, the tongue, the skin — or obtained from other neurons, to the central nervous system, or to another neuron.
Away from the centre
Transmitting impulses from the central nervous system to the effectors — the muscles.
The chain, end to end
A stimulus arrives at a receptor. A neuron carries it to the central nervous system. Something there decides what to do. Another neuron carries the instruction out to a muscle, and the muscle contracts. Receptor, neuron, centre, neuron, effector — and the effector is muscle tissue, which is the skill you have just finished.
Two of this chapter’s four animal tissues are in that sentence
Nervous tissue carries the message and muscle tissue carries it out. Neither is any use without the other: a signal with nothing to act on changes nothing, and a muscle with no signal never moves. The two tissues were designed against each other.
This is the machinery behind co-ordination
Grade 10 gave you stimulus and response as a table to fill in, with nerves and muscles named but not explained. You now have both of them as tissues, with cells, structures and reasons. The table has a mechanism underneath it.