Have you ever wondered how cannabis (A.K.A. marijuana, weed, pot, Mary Jane, etc.) gets people acting either relaxed, sluggish, and in the mood for a nap or excited, twitchy, and talkative? The answers are all intertwined within the science of how the human body and brain works with the chemicals in the plant.

The Marijuana plants


Figure 1: The three Cannabis plant species

Marijuana, which is a popular name used for the three plant species Cannabis sativa, Cannabis indica, and Cannabis ruderalis, is composed of more than 60 chemical constituents called cannabinoids. The most well-known components are delta-9-tetrahydrocannabinol (Figure 2), which is abbreviated to THC and contributes more to the “high” of the drug, and cannabidiol and cannabinol (Figures 3 and 4, respectively), which are components that aid in relaxation and produce less psychoactive effects. What is also important to note is that higher levels of THC are found around the flowering part of the female plant. The female plant’s leaves and majority of the male plant have a lower level of THC and the stalks and seeds of both sexes have almost zero.


Figure 2: Delta-9-Tetrahydrocannabinol, Figure 3: Cannabidiol, Figure 4: Cannabinol

The chemical effects of Marijuana

The effects of THC are the result of their binding to the cannabinoid receptors, called CB1 and CB2. Large amounts of CB1 are located in the cerebral region and are responsible for the psychoactive effects when activated. Aspects of memory retention, pain sensation, strength of appetite, and blood pressure control are altered due to the connection made with these receptors. CB2 receptors are mostly found in the immune system and work to improve anti-inflammation, which is strongly thought to be an element of many medical conditions.

The two most common species of cannabis are Cannabis sativa and Cannabis indica. The approximate ratio of the chemicals from these plants may have one dominant or other and is a hybrid mix of the two species. A dominant amount of C. sativa has a higher levels of THC and therefore produces more psychoactive effects, while strains with a dominant amount of C. indica have high levels of cannabidiol and therefore produce a more internally analgesic environment.

A precursor of THC, tetrahydrocannabinolic acid (THCa) is a non-psychoactive cannabinoid and is the most abundant cannabinoid in cannabis plants. The process used to convert THCa to THC is called decarboxylation: It involves heating the plant to a specific high temperature for a particular amount of time to lose a piece of the original molecule, in this instance carbon dioxide (CO2) (Figure 5).


Figure 5: Decarboxylation Reaction of Delta-9-Tetrahydrocannabinol

Delivery of Marijuana

The most common and fastest way to push the chemicals into the bloodstream is through inhalation (i.e., heating to a high temperature and smoking the plant). The reason behind this is that as the smoke enters the lungs through the alveoli, tiny air sacs that line the lungs. The efficiency with which the alveoli absorb the compounds is due to their large surface area. The compounds are then released into the bloodstream, travel throughout body, and spread the “high.”

Another way to spread the drug inside the body is to ingest the plant matter after it has been cooked properly and the chemical components have been activated. Since THC is fat-soluble, it’s not as easy as pouring boiled water and making tea as with regular tea leaves. Having a fat-soluble compound such as oil or butter mixed in with the still-carboxylated plant, and once again using a large amount of either natural or synthetic heat to help with the extraction of the CO2, is what must be done to bring out the THC, which will then create the euphoric high once ingested and absorbed into the bloodstream.

The legal and medical use of cannabis

Even though cannabis usage might cause behaviors that aren’t typical of everyday situations, researchers around the world have found cannabis to be quite beneficial. This is especially true when the user is a medical patient and is suffering from joint aches, muscle pains, or more serious conditions such as cancer or anorexia.


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