The endocannabinoid system, explained by exploring your own body
Every person reading this has an endocannabinoid system. It is a network of tiny switches, messengers and clean-up crews that keeps the body steady. Tap any part of the body below to see which switches sit there and what they do.
Why this matters
Start here
Three parts, one job: keeping you steady
Your body is a colony of billions of cells. Each cell has its own needs, and they all have to work together. To do that, cells send each other chemical messages. The endocannabinoid system, often shortened to ECS, is one of those messaging networks.
Scientists often describe it as a lock and key. The is the lock, sitting on the outside wall of a cell. The messenger molecule is the key. When the right key turns the right lock, something changes inside that cell.
The three parts
- The locks (receptors). Two main ones, called CB1 and CB2. They sit on cell surfaces all over the body and each one changes what its cell does.
- The keys (endocannabinoids). Fatty messenger molecules your body builds itself. The two main ones are anandamide and 2-AG.
- The clean-up crew (enzymes). Tools that build the keys when they are needed and destroy them seconds later. The main destroyers are called FAAH and MAGL.
The part that surprises people
Most messaging systems keep a stock of messengers ready in tiny bags, waiting to be released. The ECS does not. Endocannabinoids are made on demand, cut fresh out of the fatty wall of the cell at the exact moment they are needed, used on the spot, and then broken down. Nothing is stored and nothing travels far.
That is why the ECS is so precise. It does not act on the whole body at once. It acts in one small place, for a short time, only where something needs correcting.
The word for it is homeostasis. It means keeping the inside of your body steady even when things outside change. Not too hot, not too cold. Not too much pain signal, not too little. The ECS is one of the body's main tools for doing that.
Where the plant comes in
The keys your body makes fit the locks perfectly. Compounds from the cannabis plant, called , are shaped closely enough to fit the same locks, but they are not identical. Researchers sometimes call them a false key. They turn the lock, but not in quite the same way, not in the same place, and not for the same length of time.
That single idea explains almost everything else on this page. Cannabis does not create new effects in the body. It leans on a control system that is already running.
It is not the cannabis plant that has many effects, it is the endocannabinoid system that determines them.Dr Mariano Garcia de Palau, Fundacion CANNA
Interactive body map
Where the receptors are, and what they do there
Tap a numbered marker on the body, or a name in the row underneath. CB1 markers are green, CB2 markers are purple, and places with a real mix of both are teal.
A note on the drawing. The illustration shows the main organs from the front. Each marker sits over the area that region covers, so a few point at parts that sit deeper in the body. The immune marker sits on a cluster of lymph nodes, and nerves and skin reach everywhere, so those markers show one place out of many.
Step by step
How one nerve cell tells another to calm down
Nerve cells talk across a tiny gap called a synapse. Normally messages travel one way. The ECS is unusual: its message travels backwards. Step through it below.
Why the backwards direction matters. The cell that is getting too much noise is the one that turns the volume down, at the exact synapse where the noise is coming from. Nothing else in the body is affected. This is called retrograde signalling, and it is the reason cannabinoids can quieten over-firing nerves without shutting the whole nervous system down.
The cast
The makers, the messengers and the breakers
Six molecules do most of the work. Two carry the message, two build them, two destroy them. Tap any name.
The others, in brief
Anandamide and 2-AG get the attention, but the body makes more:
- Noladin ether and virodhamine, both weaker relatives. Virodhamine may work against CB1 rather than with it.
- N-arachidonoyl dopamine, which also triggers heat and pain sensors.
- Oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). These do not bind the cannabinoid receptors at all, but behave in a similar way. PEA calms inflammation and OEA reduces appetite.
Where it all comes from
Endocannabinoids are built from a fatty acid called arachidonic acid, which sits in the wall of almost every cell.
That fatty acid signalling system is ancient. Plants use a version of it to defend against infection and to signal stress. Animals use it for muscle growth, blood clotting, widening blood vessels and inflammation. The ECS looks like an upgraded version of the same idea, which is why it is found so widely across the animal kingdom.
Homeostasis
What the system is actually balancing
One system, many neighbours
The ECS does not work on its own. It sits above other messaging systems and adjusts them. It can change the release of acetylcholine, dopamine, GABA, histamine, serotonin, glutamate, noradrenaline, prostaglandins and the body's own opioid chemicals.
That is why one system can affect so many different things, and why the effects of cannabis are so varied from person to person. The ECS is less like a single switch and more like a hand on a mixing desk, nudging many sliders at once.
Plant compounds
Which plant compound fits which lock
The bars show roughly how strongly each compound binds each receptor, not how useful it is. Tap any row and the detail opens directly underneath it.
| Compound | At CB1 | At CB2 | What it does | Studied for |
|---|
Studied for does not mean proven or approved. The last column lists conditions where research exists. In the UK, only a small number of cannabis medicines are licensed, and most prescriptions are unlicensed and specialist-led. Nothing here is a recommendation.
Working together
The entourage effect
What the evidence does and does not say
The idea has a real basis. It was first described in 1998, when researchers found that fatty molecules with no activity of their own still made 2-AG work better. Later work suggested that terpenes, the compounds that give cannabis its smell, might change how cannabinoids behave.
But the strength of the effect in people taking medicine is still being argued about. Some laboratory findings have not been repeated at the concentrations found in real products. Honest summary: the interaction between cannabinoids is well supported, and the wider terpene story is promising but not settled.
For patients. This is why two products with the same delta-9-THC and cannabidiol numbers on the label can still feel different. The rest of the plant is not the same in both.
The wider system
Beyond CB1 and CB2
For a long time the ECS meant two receptors, two messengers and two enzymes. It is now clear the system is bigger than that. Researchers sometimes call the fuller picture the endocannabinoidome.
At the prescribing end
What the physiology means in clinic
Written for healthcare professionals, but in plain words so patients can follow the same reasoning.
A caution from history. A medicine called rimonabant was designed to block CB1 to treat obesity. It worked on weight, but it was withdrawn in 2008 because it caused low mood and suicidal thinking in some people. Turning this system down across the whole body has real consequences, and it is a reminder that a receptor being present is not the same as a receptor being a safe target.
Knowledge check
Ten questions to test yourself
Ten quick questions, one at a time
Each answer is explained as you go, with the source it comes from. It takes about three minutes.
Understanding the science is the first step
If you want help working out what to ask your clinic, or you want to share what happened to you, we are here. Patients first, always.
References
References follow the Harvard style. Sources with no confirmed author are listed by their publishing body. Numbers in the interactive panels above match this list.
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