Human Physiology/The Nervous System

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Drugs

A drug is, generally speaking, any substance that changes the way your body works. Some drugs have a medicinal

effect, and some are used recreationally. They have diverse effects, depending on the drug. Drugs can do anything

from diminish pain, to preventing blood clots, to helping a depressed person.

Different drugs work in different ways, called the mechanism of action, the drugs covered here will all act on the

nervous system via receptors on different neurons. There are also drugs that change how enzymes work, but that's

not part of the nervous system (at least directly) and will not be discussed here.

You've probably heard the terms stimulant (excitatory) and depressant (inhibitory). This is a broad way of classifying

drugs that work on the CNS. Depressants slow down neural function, and stimulants speed it up.

Most of the common depressants (including alcohol, benzodiazepines, barbiturates and GHB) work on GABA

receptors, although there are others. Opiates, for example, work on mu opioid receptors and also produce inhibitory

effects, and some antipsychotics block serotonin. See the alcohol section below to see one way this can work.

Stimulants work mostly with epinephrine, dopamine or serotonin (or a combination of them). Many of them either

mimic one, or stop them from leaving the synapse, causing more action potentials to be fired. Methamphetamine,

discussed below, is a fairly typical stimulant drug.

Drug Abuse

Scientists have long accepted that there is a biological basis for drug addiction, though the exact

mechanisms responsible are only now being identified. It is believed that addictive substances

create dependence in the user by changing the brain's reward functions, located in the mesolimbic

dopamine system

—

the part of the brain that reinforces certain behaviors such as eating, sexual

intercourse, exercise, and social interaction. Addictive substances, through various means and to

different degrees, cause the synapses of this system to flood with excessive amounts of dopamine,

creating a brief rush of euphoria more commonly called a "high

”

. Some say that abuse begins when the user begins

shirking responsibility in order to afford drugs or to have enough time to use them. Some say it begins when a person

uses "excessive" amounts, while others draw the line at the point of legality, and others believe it amounts to chronic

use despite degenerating mental and physical health in the user. Some think that any intoxicant consumption is an

inappropriate activity. Here are some drugs that are abused frequently: Acid/LSD, Alcohol, various tryptamines and

phenethylamines, Cocaine, Ecstasy/MDMA, Heroin, Inhalants, Marijuana, Methamphetamine, PCP/Phencyclidine,

Prescription Medications, Smoking/Nicotine and Steroids.

Alcohol

Alcohol is, and has been for thousands of years, one of the most commonly used drugs in the world. It is legal, with

some restrictions and exceptions, nearly everywhere. It is a common misconception that somehow alcohol is 'better'

or 'safer' than other recreational drugs. This is simply NOT the case. Alcohol is a depressant, and as such it has the

potential to cause coma, respiratory depression/arrest and possibly death. Compared with some other (illegal in most

places) drugs of recreational value (such as marijuana, serotonin based hallucinogens like LSD or psilocybin)

alcohol is far more toxic and has more risk of overdose. That doesn't mean that moderate drinking will probably hurt

you, though, either.

Short term effects from drinking (listed roughly as they appear, and as dosage goes up) are: decreased inhibitions and

thusly judgment, flushing of the face, drowsiness, memory problems begin, severe motor impairment, blurry vision,

dizziness, confusion, nausea, possible unconsciousness, coma, death (due to respiratory arrest or possibly aspiration

on vomit).

Alcohol produces these effects mainly via the GABA receptors in the brain. When GABA (or in this case alcohol)

binds to it's receptor, it lets either Cl- ions in, or K+ out. This is called hyperpolarization, or an inhibitory