Spider BrainOne of the most amazing things about spiders is how much they can accomplish with such a small brain. The spider's central nervous system is made up of two relatively simple ganglia, or nerve cell clusters, connected to nerves leading to the spider's various muscles and sensory systems. The simple instructions encoded in these nerve cells give spiders all the information they need to undertake complex tasks, such as building webs and attacking prey. Some species even exhibit learning behavior. If something isn't working -- a web in a particular spot, for example -- the spider will give up the activity and try something new.