As research uncovers more and more about the various effects of CBD and cannabis a question has come up – what is it that causes one plant to have such an array of effects?

The answer lies in a previously undiscovered physiological system in the human body, named after the compounds that led to its discovery. And it seems that this system, the endogenous cannabinoid, or endocannabinoid, system is hugely important in human physiology. 

The system is made up of cells that send messages and receiver cells that receive the message and effect the appropriate action.

Cannabinoids are neurotransmitters that send messages to special cannabinoid receptors.  Both are found throughout the central and peripheral nervous system and it’s these cannabinoids and their receptors that make up the endocannabinoid system.  ‘Endo-‘ simply means ‘within’ or ‘internal’ and thus refers to the understanding that cannabinoids already occur naturally within the body, rather than those added when you ingest cannabis. 

Endocannabinoid system cells and receptors are found all over the body… in the brain, organs, connective tissues, glands, and immune cells.  And each performs a different function within the system.  Scientists have also discovered two main receptor types – CB1 and CB2.  Based on the information given by the receptor the cell will respond in a given way, and different receptors have a different effect.


Endocannabinoids in Action


Neurons, the cells found in the central nervous system, are part of a linked network of cells that respond and listen to their environment. 


And if a sender cell is firing too much the receiver cell releases endocannabinoids to effectively limit the messages coming from the sender cell and ‘calm’ it.   It helps create an environment in the body where everything is working at ‘just right’ levels.


This process is called Homeostasis – and all biological systems are designed to operate within narrow ranges to create this perfect environment within.  We’re not too hot, too cold and we fight infection – homeostasis ensures the balance and regulates the systems within us.


But while each part of the Endocannabinoid System performs a different function on the cells it reacts with, the goal is always homeostasis, harmony


It is, for example, a cell’s response to the stimulus of bright light that causes sensitivity in an eye. The cell is given a message from a nearby cell, via the receptor, and the cell reacts based on the information it receives.


In another example research (1) has shown that endocannabinoids are released when the immune cells are activated.  When an infection attacks the immune cells, the immune cells call for backup from more immune cells.  It is understood that endocannabinoids are released here to maintain the natural balance.


This might on the face of it seem strange – if there are more immune cells to fight the infection, the better… but if immune cells fire too much they can begin to fire at healthy cells, not just the infected ones. Inflamation is an example of the immune system’s defence against dangers, but issues with a runaway immune system are known as autoimmune diseases and include conditions such as arthritis or multiple sclerosis.  Endocannabinoids are released to maintain the balance.


An introduction to the Endocannabinoid System

Endocannabinoids as Retrograde Signals


One important  thing that makes endocannabinoids so different from regular messages between cells is their direction of travel.  When cells send messages it is usually in one direction – from sender cell to receiver cell.  Endocannabinoids are sent in the opposite direction – from receiver to original sender, in response to the original message.  This is called Retrograde Signalling.


And in this lies cannabinoids’ greatest strength…


… their ability to supress responses from sender cells preventing them over-firing.  It means they are continually regulating the body’s systems to create homeostasis.


The cannabis plant also uses cannabinoids to defend itself. Cannabinoids have antioxidant properties that protect the leaves and flowers from UV radiation by neutralising free radicals from ultraviolet rays.


Cannabinoid Receptors


Scientists have discovered two major cannabinoid receptors CB1 and CB2.  There are more of this type of receptor but not only were they found first and have been studied the most.  CB1 was discovered in 1990 and three years later scientists discovered the second receptor.


These receptors are what cause the cannabinoids to activate, by three types of cannabinoids; those produced naturally by the mammalian system, those produced by the cannabis plant and synthetic cannabinoids.


And, according to some research, adding cannabis to these receptors generates even more receptors - smaller doses have a larger effect.


While both receptors are found throughout the body.  CB1 receptors are found in abundance in the brain and spinal cord, whereas CB2 receptors are found outside of the nervous system, in places such as white blood cells in the immune system.


One important thing about these receptors is that they are not found in the region of the brain that controls the heart or lung function, and this is believed to be the reason why fatal overdoses of cannabis don’t occur.


For more on the research around cannabidiols read our blog Cannabidiol, Researching the Effects.



(1)        Endocannabinoids and Immune Regulation, Pandy et al

A brief guide to the Endcannabinoid System