Following the suspected chemical weapons attack in Syria, ABC Science has an informative interview with Dr. David Caldicott, an emergency physician and senior lecturer at the Australian National University.
According to Caldicott, weapons-grade chemicals such as sarin are "possibly some of the most dangerous things that humans have ever made, after the atom bomb." These chemicals, known as organophosphates, act on the body's involuntary nervous system. Caldicott elaborates:
You can imagine that if you block one of the major 'off-switches' of the body, and are left with all the lights turned 'on' all of the time, the body might run into trouble. With an extremely rapid build up of acetylcholine in the synapse, things like secretions, respiratory problems, and muscular dysfuntion can go on unattenuated. And that's really how people suffer and die.
Read more here.