Homeostasis is the concept that biological systems are actively regulated to maintain conditions and functions within a narrow range. For example, human bodies don’t function as well in conditions where the temperature is either too hot or too cold, blood sugar levels are too high or too low, etc. Conditions need to be just right for cells to maintain optimum performance, and exquisite systems have evolved to draw them back into balance if they move out. One such system, the endocannabinoid system (ECS), is a vital molecular system that helps maintain homeostasis.

The ECS is found in all vertebrate species, including humans. Because of its crucial role in homeostasis, the ECS is widespread throughout the animal kingdom.

There are three key components to the ECS:

  1. Endocannabinoids, small molecules that activate cannabinoid receptors
  2. Metabolic enzymes that break down endocannabinoids after they are used
  3. Cannabinoid Receptors, sit on the surface of cells and “listen” to conditions outside the cell, then transmit information about changing conditions to the inside of the cell, kick-starting the appropriate cellular response.

Endocannabinoids are molecules that bind to, and activate, cannabinoid receptors. Endocannabinoids are produced naturally by cells in the human body (“endo” means “within,” as in within the body). There are two major endocannabinoids: anandamide and 2-AG. These endocannabinoids are made from fat-like molecules within cell membranes, and are synthesized on-demand, meaning they are made and used exactly when they’re needed, rather than packaged and stored for later use like certain other biological molecules.

Metabolic enzymes quickly destroy endocannabinoids once they’ve been used. The two big enzymes are FAAH, which breaks down anandamide, and MAGL, which breaks down 2-AG. These enzymes ensure that endocannabinoids get used when they’re needed, but not for longer than necessary. This distinguishes endocannabinoids from many other molecular signals in the body, such as hormones or classical neurotransmitters, which can persist for many seconds or minutes, or get packaged and stored for later use.

There are two major cannabinoid receptors: CB1 and CB2. These aren’t the only cannabinoid receptors, but they were the first ones discovered and remain the most prominent, and the best-studied.

  • CB1 receptors are among the most abundant receptor types in the brain. These are the receptors that interact with THC to get people high.
  • CB2 receptors are more abundant outside of the nervous system, in places like the immune system.

*both receptors are found throughout the body

These three key components of the ECS are found within almost every major system of the body. When something brings a cell out of homeostasis, these three pillars of the ECS bring things back, thus maintaining homeostasis. Because of its role in helping bring things back to homeostasis, the ECS is typically engaged only when and where it’s needed.

Endocannabinoids travel backward, which is why they’re known as retrograde signals. Most of the time, information flow between neurons is strictly in one direction. Endocannabinoids allow receiver neurons to regulate how much input they’re getting, and they do this by sending retrograde signals (endocannabinoids) back to overactive sender neurons.

The brain isn’t the only organ that needs to maintain homeostasis. Every system of the body, from the digestive to the immune system, needs to carefully regulate how its cells are functioning. Proper regulation is crucial for ensuring survival.