spiders do not have a centralized nervous system
some spiders care for their young for example a wolf spiders brood clings to rough bristles on the mothers back and females of some species respond to the begging behaviour of their young by giving them their prey provided it is no longer struggling or even regurgitate food
 there is an anatomical convention that a cluster of neurons in the brain or spinal cord is called a nucleus whereas a cluster of neurons in the periphery is called a ganglion