Human Physiology/The Nervous System

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Marijuana

Cannabis sativa.

Marijuana contains a myriad of chemicals, called

cannabinoids, that have psychoactive and medicinal

effects when consumed, the major one being

tetrahydrocannabinol (THC). THC serves to mimic the

endogenous neurotransmitter anandamide (also found in

chocolate) at the CB

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receptors in the brain. Other

cannabinoids include Cannabidiol (CBD), cannabinol

(CBN) and tetrahydrocannabivarin (THCV). Although

THC is found in all parts of the plant, the flower of the

female plant has the highest concentration, commonly

around eight percent. The flowers can be used, or they

can be refined. Trichomes contain most of the THC on

the flowers and can be removed by a few different

methods. These removed trichomes are called kief. Kief

can, in turn, be pressed into hashish. By far the most

common way to consume any of these products is by

smoking, but it can be taken orally as well.

Cannabis has a very long, very good safety record.

Nobody on record has ever died because of marijuana,

directly at least. It is estimated that it would take 1-1.8

kilograms of average potency marijuana, taken orally, to

have a fifty percent chance of killing a 68kg human.

Despite this, the possession, use, or sale of psychoactive

cannabis products became illegal in many parts of the

world in the early 20th century. Since then, while some countries have intensified the enforcement of cannabis

prohibition, others have reduced the priority of enforcement to the point of de facto legality. Cannabis remains illegal

in the vast majority of the world's countries.

The nature and intensity of the immediate effects of cannabis consumption vary according to the dose, the species or

hybridization of the source plant, the method of consumption, the user's mental and physical characteristics (such as

possible tolerance), and the environment of consumption. This is sometimes referred to as set and setting. Smoking

the same cannabis either in a different frame of mind (set) or in a different location (setting) can alter the effects or

perception of the effects by the individual. Effects of cannabis consumption may be loosely classified as cognitive

and physical. Anecdotal evidence suggests that the Cannabis sativa species tends to produce more of the cognitive or

perceptual effects, while Cannabis indica tends to produce more of the physical effects.