Joni Kamiya, The quote is from a National Pesticide Information Center fact sheet that you yourself cited.  Here's more:

"How does chlorpyrifos work?

Chlorpyrifos can be harmful if it is touched, inhaled, or eaten. Chlorpyrifos works by blocking an enzyme which controls messages that travel between nerve cells. When the enzyme is blocked, the nervous system can't send normal signals. This causes the nervous system to malfunction and this is how it eventually kills the pest."