Squids are invertebrates, meaning they have a “simple” nervous system compared to adults, no Central Nervous System (CNS). Meaning no Brain and no vertebrae (spine). As we dive into neurons (brain cells) and neural networks (groups of activity involving many neurons and brain regions) we will discuss a simple system comprised of a sensory input, intermediate, and motor output. Think about reflexes, these are are automatic, and don’t require conscious control. How about simple lego robots with a light sensor, central computer, output motors – see here!
Axon = a nerve fiber carrying electrical impulses or signal for a neuron.
More info @ http://scientopia.org/blogs/bridgeblog/2011/09/30/a-neuroscience-field-guide-the-squid-giant-axon/