Cannabinoids interact with different cannabinoid receptors in the body, sometimes in tandem and sometimes in competition. Each activation gives a response to dampen pain stimuli and reduce inflammation.
The most well known cannabinoid receptors, CB1 and CB2, are proteins that are imbedded in the membrane of cells. These surface proteins are then attached to another protein that determines the signaling direction: activation or inhibition. The signal that goes out will depend on which molecule (THC, for example, will activate) that binds to the receptor. There are, however, many other receptors in the human body that are activated by cannabinoids.