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marijuana and the nervous system

Neuroscience For Kids

marijuana

Marijuana is one of the world’s most commonly used illegal drugs. There are approximately 300 million users worldwide and 28 million users in the United States (Diaz, 1997). Marijuana comes from a plant called “Cannabis sativa.” The chemical in this plant that produces the altered states of consciousness is called “delta-9 tetrahydrocannabinol” or “THC.” Marijuana is usually smoked like a cigarette, but it can also be cooked into baked goods like brownies or cookies or brewed like a tea. THC is also contained in “hashish” (hash) which is the resin from the marijuana plants. Hash is usually smoked in a pipe. Other names for marijuana include: grass, pot, reefer and weed.

Effects of Marijuana on the Nervous System

THC acts on cannabinoid receptors which are found on neurons in many places in the brain. These brain areas are involved in memory (the hippocampus), concentration (cerebral cortex), perception (sensory portions of the cerebral cortex) and movement (the cerebellum, substantia nigra, globus pallidus). When THC activates cannabinoid receptors, it interfers with the normal functioning of these brain areas. In low to medium doses, marijuana causes:

  • relaxation
  • reduced coordination
  • reduced blood pressure
  • sleepiness
  • disruption in attention
  • an altered sense of time and space. a good reason not to drive or operate machinery while under the influence.

In high doses, marijuana can cause:

  • hallucinations
  • delusions
  • impaired memory
  • disorientation.

Scientists have known for a long time that THC interacted with cannabinoid receptors in the brain, but did not know why the brain would have such receptors. They thought that the brain must make some kind of substance that naturally acted on these receptors. In 1992, they found the answer. anandamide. Anandamide is the brain’s own THC (just like “endorphin” is the brain’s own morphine). Still, scientists are not sure what the function of anandamide is in the normal brain.

The effects of marijuana start as soon as 1-10 minutes after it is taken and can last 3 to 4 hours or even longer. Experiments have shown that THC can affect two neurotransmitters: norepinephrine and dopamine. Serotonin and GABA levels may also be altered.

Whether marijuana can produce addiction is controversial. Also controversial is whether marijuana causes long-term mental abnormalities. Only future research will give us the answers. It is interesting to note that there are NO documented cases of a fatal overdose produced by marijuana. However, because there is a high level of tar and other chemicals in marijuana, smoking it is similar to smoking cigarettes. The lungs get a big dose of chemicals that increase the chances of lung problems and cancer later in life.

How long does THC stay in your body and for how long can it be detected after you use marijuana?

The amount of time depends on several factors such as how much a person has smoked, how long a person has smoked for, and the method used to detect THC or its metabolites. Marijuana can be detected in urine, blood and saliva using methods called thin layer chromatography, high pressure liquid chromatography, gas chromatography, enzyme immunoassay and radioimmunoassay. The most psychoactive ingredient in marijuana is delta-9-tetrahydrocannabinol (THC). THC is broken down into several other compounds that are also psychoactive. The half-life of THC is about 24 hours. However, the metabolites of THC can be detected for 45 to 60 days after the last use.

According to Maistro et al., in the book Drug Use and Misuse (1991):

“Approximately half of the THC is excreted over several days, and the remainder by the end of about a week. However, some metabolites of the THC, a number of which may still be active in the system, can be detected in the body at least thirty days following ingestion of a single dose and, following chronic use, in the urine for several weeks.”

  • In 1969, the Journal of the American Medical Association (JAMA, vol. 207, pages 1349-1350, 1969) published a paper that described the psychoactive effects of catnip in people. People who smoked catnip were said to become happy and relaxed. Catnip (from the plant Nepeta cataria) does cause most cats to act strangely: they roll around, shake their heads, rub against things, and try to get the plant all over their bodies. Interestingly, cats are only affected when they smell it – it has no effect if they eat it. It appears that catnip has little or no psychoactive effects in people. Actually, in the 1969 JAMA paper, the authors mislabeled the pictures of marijuana and catnip. They labeled the pictures of marijuana as catnip and that of catnip as marijuana.
  • THC was identified as the major psychoactive chemical in marijuana in 1964.
  • Marijuana contains more than 400 different chemicals.

Take a short on-line, interactive quiz about amphetamines, cocaine and marijuana.

For more information about marijuana, see:

  1. Marijuana Detection Windows
  2. Diaz, J. How Drugs Influence Behavior. A Neuro-Behavioral Approach, Upper Saddle River (NJ): Prentice Hall, 1997.
  3. Marijuana: Facts for Teens – from the National Institute on Drug Abuse
  4. Marijuana: Facts for Parents – from the National Institute on Drug Abuse
  5. Marijuana Update from the National Institute on Drug Abuse.
  6. Is CBD Oil Legal?

Copyright © 1996-2020, Eric H. Chudler All Rights Reserved.

Intended for elementary and secondary school students and teachers who are interested in learning about the nervous system and brain with hands on activities, experiments and information.

The Effects of Marijuana on Your Body

Marijuana is made from the shredded and dried parts of the cannabis plant, including the flowers, seeds, leaves, and stems. It’s also known as pot, weed, hash, and dozens of other names. While many people smoke or vape it, you can also consume marijuana as an ingredient in food, brewed tea, or oils.

Different methods of taking the drug may affect your body differently. When you inhale marijuana smoke into your lungs, the drug is quickly released into your bloodstream and makes its way to your brain and other organs. It takes a little longer to feel the effects if you eat or drink marijuana.

There is ongoing controversy around the effects of marijuana on the body. People report various physical and psychological effects, from harm and discomfort to pain relief and relaxation.

Here’s what happens to your body when this drug enters your bloodstream.

Marijuana can be used in some states for medical reasons, and in some areas, recreational use is legal as well. No matter how you use marijuana, the drug can cause immediate and long-term effects, such as changes in perception and increased heart rate. Over time, smoking marijuana may cause chronic cough and other health issues.

The effects of marijuana on the body are often immediate. Longer-term effects may depend on how you take it, how much you use, and how often you use it. The exact effects are hard to determine because marijuana has been illegal in the U.S., making studies difficult and expensive to conduct.

But in recent years, the medicinal properties of marijuana are gaining public acceptance. As of 2017, 29 states plus the District of Columbia have legalized medical marijuana to some extent. THC and another ingredient called cannabidiol (CBD) are the main substances of therapeutic interest. The National Institutes of Health funded research into the possible medicinal uses of THC and CBD, which is still ongoing.

With the potential for increased recreational use, knowing the effects that marijuana can have on your body is as important as ever. Read on to see how it affects each system in your body.

Much like tobacco smoke, marijuana smoke is made up of a variety of toxic chemicals, including ammonia and hydrogen cyanide, which can irritate your bronchial passages and lungs. If you’re a regular smoker, you’re more likely to wheeze, cough, and produce phlegm. You’re also at an increased risk of bronchitis and lung infections. Marijuana may aggravate existing respiratory illnesses, such as asthma and cystic fibrosis.

Marijuana smoke contains carcinogens, so it may increase your risk of lung cancer too. However, studies on the subject have had mixed results. According to the National Institute of Drug Abuse (NIDA), there is no conclusive evidence that marijuana smoke causes lung cancer. More research is needed.

THC moves from your lungs into your bloodstream and throughout your body. Within minutes, your heart rate may increase by 20 to 50 beats per minute. That rapid heartbeat can continue for up to three hours. If you have heart disease, this could raise your risk of heart attack.

One of the telltale signs of recent marijuana use is bloodshot eyes. The eyes look red because marijuana causes blood vessels in the eyes to expand.

THC can also lower pressure in the eyes, which can ease symptoms of glaucoma for a few hours. More research is needed to understand the active ingredients in marijuana and whether it’s a good treatment for glaucoma.

In the long term, marijuana has a possible positive effect on your circulatory system. Research isn’t conclusive yet, but marijuana may help stop the growth of blood vessels that feed cancerous tumors. Opportunities exist in both cancer treatment and prevention, but more research is needed.

The effects of marijuana extend throughout the central nervous system (CNS). Marijuana is thought to ease pain and inflammation and help control spasms and seizures. Still, there are some long-term negative effects on the CNS to consider.

THC triggers your brain to release large amounts of dopamine, a naturally occurring “feel good” chemical. It’s what gives you a pleasant high. It may heighten your sensory perception and your perception of time. In the hippocampus, THC changes the way you process information, so your judgment may be impaired. The hippocampus is responsible for memory, so it may also be difficult to form new memories when you’re high.

Changes also take place in the cerebellum and basal ganglia, brain areas that play roles in movement and balance. Marijuana may alter your balance, coordination, and reflex response. All those changes mean that it’s not safe to drive.

Very large doses of marijuana or high concentrations of THC can cause hallucinations or delusions. According to the NIDA, there may be an association between marijuana use and some mental health disorders like depression and anxiety. More research is needed to understand the connection. You may want to avoid marijuana if you have schizophrenia, as it may make symptoms worse.

When you come down from the high, you may feel tired or a bit depressed. In some people, marijuana can cause anxiety. About 30 percent of marijuana users develop a marijuana use disorder. Addiction is considered rare, but very real. Symptoms of withdrawal may include irritability, insomnia, and loss of appetite.

In people younger than 25 years, whose brains have not yet fully developed, marijuana can have a lasting impact on thinking and memory processes. Using marijuana while pregnant can also affect the brain of your unborn baby. Your child may have trouble with memory, concentration, and problem-solving skills.

What happens when you smoke or ingest marijuana? Learn the effects it has on your body with this interactive graphic. ]]>