http://www.venomousreptiles.org/articles/97

Great article that explains it better and in more scientific terms than I've seen most anywhere else. As to whether or not you could develop a "tolerance" to a neruo versus a hemotoxin...I really couldn't say. I know there is research being conducted into using the protein compounds in various venoms for treatment of nerve damage as well as heart/cardio issues, etc., among other things. One of my family members worked on the team for Eli Lilly that isolated the compound in Gila monster venom to develop a new drug to treat Type II diabetes, so who knows what could be done with some of the compounds in venom and/or how it would work on the human body in controlled doses? Pretty fascinating, you ask me.