2major cell groups make up the nervous neurons and connective tissue cells such as astrocytes and schwann cells. which are "nervous" cells? why? what are the major functions of the other group?

Neurons with their somas (bodies), axons, and synapses represent the nervous cells, while astrocytes and Schwann cells represent glia cells. Nervous cells transmit messages to each other in order for us to be able to function as we to - move, talk, hear, see, think, etc. 

The major function of glia cells is that they provide structural support for our brain, they make communication faster but they also have an important functional role.