Whether our reasons have been medical, spiritual, or recreational, we've been using cannabis as a species for thousands of years. However, it wasn't until recently that we've started to understand how marijuana affects us in so many ways. Here we briefly describe what is known as the endogenous cannabinoid system (or endocannabinoid system) that is present in almost all vertebrates.
Discovered piece by piece since the 1960s, the endocannabinoid system (ECS) works to promote homeostasis, which in a biological sense is stable internal environment despite external fluctuations and circumstances. The ECS is composed of a huge network of receptors throughout much of the body (including the brain and other organs, connective tissues, glands, and the central and peripheral nervous systems) and even though these receptors do different things the aim of achieving homeostasis at every level of the body is always the same.
The ECS does this through a vast system of receptors (the two most well-known are CB1 and CB2) on the surface of cell membranes throughout the body, endocannabinoids created by the body on demand (the two most-studied are anandamide and 2-arachidonoylglycerol), and metabolic enzymes called fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) that break down cannabinoids once used. CB1 receptors are predominantly found in the central nervous system, glands, and organs while CB2 receptors are mainly found in tissues associated with the immune system. However, it's believed that the ECS has more receptors than any other system in the human body, and many tissues have both CB1 and CB2 receptors, each providing its own specific action depending on the site.
This account by no means describes all the known nuances of the ECS and the effects it has shown in many physiological functions. The identification of the ECS led us to understand that our bodies harbor a vast biological system made specifically for interactions with active chemical compounds ourselves (endocannabinoids) and similar compounds we find in cannabis plants (phytocannabinoids). To end, it's no secret that cannabis does unpredictable things to the human body, so there's no guarantee that activating one's ECS with marijuana will produce the desired effect, but as our understanding of the way various cannabis strains affect our ECS we can make use of them in the best way possible.