A dry, shredded green/brown mix of flowers, stems, seeds, and leaves of the hemp plant Cannabis sativa, it usually is smoked as a cigarette (joint, nail), or in a pipe (bong). It also is smoked in blunts, which are cigars that have been emptied of tobacco and refilled with marijuana, often in combination with another drug. Use also might include mixing marijuana in food or brewing it as a tea. As a more concentrated, resinous form it is called hashish and, as a sticky black liquid, hash oil.
Marijuana smoke has a pungent and distinctive, usually sweet-and-sour odor. There are countless street terms for marijuana including pot, herb, weed, grass, widow, ganja, and hash, as well as terms derived from trademarked varieties of cannabis, such as Bubble Gum, Northern Lights, Juicy Fruit, Afghani #1, and a number of Skunk varieties. The main active chemical in marijuana is THC The membranes of certain nerve cells in the brain contain protein receptors that bind to THC.
Once securely in place, THC kicks off a series of cellular reactions that ultimately lead to the high that users experience when they smoke marijuana. Scientists have learned a great deal about how THC acts in the brain to roduce its many effects. When someone smokes marijuana, THC rapidly passes from the lungs into the bloodstream, which carries the chemical to organs throughout the body, including the brain. In the brain, THC connects to specific sites called cannabinoid receptors on nerve cells and influences the activity of those cells.
Some brain areas have many cannabinoid receptors; others have few or none. Many cannabinoid receptors are found in the parts of the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement(5). Brain The short-term effects of marijuana can include problems with memory and learning; distorted perception; difficulty in thinking and problem solving; loss of coordination; and increased heart rate.
Research findings for long-term marijuana use indicate some changes in the brain similar to those seen after long-term use of other major drugs of abuse. For example, cannabinoid (THC or synthetic forms of THC) withdrawal in chronically exposed animals leads to an increase in the activation of the stress-response system(6) and changes in the activity of nerve cells containing dopamine(7). Dopamine neurons are involved in he regulation of motivation and reward, and are directly or indirectly affected by all drugs of abuse.
Other Health Effects Some of marijuana? s adverse health effects may occur because THC impairs the immune system? s ability to fight off infectious diseases and cancer. In laboratory experiments that exposed animal and human cells to THC or other marijuana ingredients, the normal disease-preventing reactions of many of the key types of immune cells were inhibited(16). In other studies, mice exposed to THC or related substances were more likely than unexposed mice to develop bacterial infections and tumors(17, 18).