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We drink one another’s health and spoil our own.
Jerome K. Jerome
Exercise 1. What do you know about alcohol?
1. What is its main active compound?
2. In what regions of the world is alcohol produced?
3. How does alcohol affect the human body?
4. What are the risks of alcohol overdose?
5. What causes hangover after drinking alcohol?
6. What is alcoholism? How quickly does it develop?
Exercise 2. Read the information about alcohol provided by NewScientist.com to check some of your answers in Exercise 1.
What is it? Ethanol produced by the action of yeast on sugars.
What does it do? Ethanol is a biphasic drug: low doses have a different effect to high doses. Small amounts of alcohol (one or two drinks) act as a stimulant, reducing inhibition and producing feelings of mild euphoria. Higher doses depress the central nervous system, initially producing relaxation but then leading to drunkenness - characterised by poor coordination, memory loss, cognitive impairment and blurred vision. Very high doses cause vomiting, coma and death through respiratory failure. The fatal dose varies but is somewhere around 500 milligrams of ethanol per 100 millilitres of blood.
How does it work? At low doses (5 milligrams per 100 millilitres of blood), alcohol sensitises NMDA receptors in the brain, making them more responsive to the excitatory neurotransmitter glutamate, so boosting brain activity. These effects are most pronounced in areas associated with thinking, memory and pleasure. At higher doses it desensitises the same receptors and also activates the inhibitory GABA system.
How long is its history?
4000BC - Wine and beer making in Egypt and Sumeria
3500BC - Bronze-age vessels show evidence of wine consumption in eastern Mediterranean
800BC - Distillation of spirits in India
AD625 - Mohammed orders his followers to abstain from alcohol
1850s - New York bartenders invent the cocktail
1920-33 - Prohibition in the US. Alcohol was also illegal in Finland from 1919 to 1932 and in various Canadian provinces at various times between 1900 and 1948.
Exercise 3. Now read more detailed information about the effects of alcohol on the brain provided by Anthony Dekker D.O., Director of Ambulatory Care and Community Health at Phoenix Indian Medical Center.
What are the effects of alcohol on the brain?
The product of the oldest chemical reaction studied by man, alcohol, continues to challenge researchers. Since the original work on alcohol's neurological effects in the early 20th century, new theories have regularly emerged. What we have learned is that alcohol is a sedative-hypnotic in the acute intoxication phase for most patients. But it diminishes the quality of sleep. Individuals with sleep apnea often experience longer and more severe apneic episodes and hypoxia, or oxygen deprivation, after drinking alcohol.
In other individuals, though, alcohol may act as a stimulant. Indeed, its association with violent and self-abusive behavior is well documented*. At intoxicating levels, alcohol is a vasodilator (it causes blood vessels to relax and widen), but at even higher levels, it becomes a vasoconstrictor, shrinking the vessels and increasing blood pressure, exacerbating such conditions as migraine headaches and frostbite. Researchers have also thoroughly documented the effects of alcohol on the developing fetus. Approximately one third of all babies born to alcoholic mothers will develop Fetal Alcohol Syndrome or Effects (FAS or FAE), causing central nervous system dysfunctions including Attention Deficit Disorder (ADD) and impaired IQ. There are also growth and facial abnormalities associated with these infants.
In the early 1900s, H. Meyer and Charles Ernest Overton originally theorized that the effect of alcohol was achieved by altering the lipid environment of cell membranes. This theory, however, requires much higher concentrations of alcohol than are clinically observed. A recent theory, supported by several researchers, pins alcohol's effect on voltage and ligand-gated ion channels that control neuronal activity. Two distinct ligand-gated channels have been identified, inhibitory ones (GABA receptors and strychnine-sensitive glycine receptors) and excitatory ones (N-methyl-D-aspartate (NMDA) and non-NMDA glutamate-activated channels and the 5HT3 subtype of serotonin receptors).
The inhibitory aspect occurs due to a hyperpolarization of neurons, secondary to an influx of chloride ions. The neuron becomes less likely to achieve the threshold membrane potential. The excitatory receptor is dependent on the NMDA and non-NMDA glutamate receptors that control the influx of sodium and calcium, which bind to endogenous neurotransmitters (glutamate or aspartate) and depolarize the neuronal membrane. The NMDA receptor seems to have a high permiability to calcium, which acts as a catalyst to several intracellular events.
Chronic exposure to alcohol seems to alter the NMDA receptors and this may play a role in the clinical symptoms of alcohol withdrawal. In vitro studies have demonstrated an increase in the binding sites for MK801 (dizocilpine) in neurons chronically exposed to alcohol. This rise may account for the acclimation process, in which greater concentrations of alcohol are needed to cause experimental and clinical symptoms of intoxication. NMDA can cause seizure activity. Mice that have been exposed to chronically elevated levels of alcohol reveal increased numbers of NMDA receptors and NMDA related seizure activity. The NMDA antagonist MK801 has been shown to decrease the severity of seizures in these mice during withdrawal. Through a complex process of cell membrane ion pumps and neurotransmitter stimulation, the multi-faceted effects of alcohol and alcohol withdrawal are becoming better understood.
*Under the influence of alcohol, the brain experiences impairments in the following regions:
•Frontal Lobe - Loss of reason, caution, inhibitions, sociability, talkativeness and intelligence.
•Parietal Lobe - Loss of fine motor skills, slower reaction time, shaking.
•Temporal Lobe - Slurred speech, impaired hearing.
•Occipital Lobe - Blurred vision, poor distance judgement.
•Cerebellum - Lack of muscle coordination and balance.
•Brain Stem - Loss of vital functions.
Exercise 4. Do you agree with the statements below? Give reasons for your choice.
Exercise 5. Some scientists argue that alcohol can produce significant positive effect on one’s health. The article below provides evidence for this point of view. Read the article and find answers to the questions:
Drink to Your Health?
By Arthur L. Klatsky
Three decades of research shows that drinking small to moderate amounts of alcohol has cardiovascular benefits. A thorny issue for physicians is whether to recommend drinking to some patients.
America has always had trouble deciding whether alcohol is a bad thing or a good thing. Millions who remember Prohibition, when all alcoholic beverages were illegal, now witness a constant stream of advertisements from producers of alcoholic beverages encouraging people to drink. Despite alcohol’s popularity today, however, many still consider abstinence a virtue. Certainly, heavy drinking and alcoholism deserve deep concern for the terrible toll they take on alcohol abusers and society in general. But worry about the dangers of abuse often leads to emotional denials that alcohol could have any medical benefits. Such denials ignore a growing body of evidence indicating that moderate alcohol intake wards off certain cardiovascular conditions, most notably heart attacks and ischemic strokes (those caused by blocked blood vessels). A few studies even show protection against dementia, which can be related to cardiovascular problems.
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