What is Alcohol?
In chemistry, an alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group. However, in layman’s terms, and for the purposes of this site the word usually refers to ethanol, also known as grain alcohol or (older) spirits of wine, or to any alcoholic beverage. Ethanol is a colorless, volatile liquid with a mild odour which can be obtained by the fermentation of sugars. An alcoholic beverage is a drink containing ethanol, commonly known as alcohol.
Ethanol is a centrally-acting drug with a depressant effect, and many societies regulate or restrict its sale and consumption. Countries place various legal restrictions on the sale of alcoholic drinks to young people. The manufacture and consumption of alcohol is found to some degree in most cultures and societies around the world, from hunter-gatherer tribes to organized nation-states. The consumption of alcohol is often important at social events in such societies and may be an important aspect of a community’s culture.
Ethanol is only slightly toxic compared to other alcohols, but has significant psychoactive effects at relatively low doses. A significant blood alcohol content may be considered legal drunkenness as it reduces attention, lengthens reaction time and lowers inhibitions. Alcoholic beverages are addictive when consumed repeatedly or in high doses and the state of addiction to ethanol is known as alcoholism.
The effects on the body
Alcohol, specifically ethanol, is a potent central nervous system depressant, with a range of side effects. The amount and circumstances of consumption play a large part in determining the extent of intoxication; e.g., consuming alcohol after a heavy meal is less likely to produce visible signs of intoxication than consumption on an empty stomach. Hydration also plays a role, especially in determining the extent of hangovers. The concentration of alcohol in blood is usually measured in terms of the blood alcohol content.
Alcohol has a biphasic effect on the body, which is to say that its effects change over time. Initially, alcohol generally produces feelings of relaxation and cheerfulness, but further consumption can lead to blurred vision and coordination problems. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every biological tissue of the body. After excessive drinking, unconsciousness can occur and extreme levels of consumption can lead to alcohol poisoning and death (a concentration in the blood stream of 0.55% will kill half of those affected). Death can also occur through asphyxiation by vomit. An appropriate first aid response to an unconscious, drunken person is to place them in the recovery position.
Intoxication frequently leads to a lowering of one’s inhibitions, and intoxicated people will sometimes do things they would not do while sober, often overlooking social, moral, and legal considerations. Conversely, some studies have suggested that intoxicated people have much greater control over their behavior than is generally recognized.
The effect alcohol has on the particualr receptors in the brain responsible for pleasurable stimulation turns from a blessing to a curse if too much alcohol is consumed. These receptors start to become unresponsive, slowing thought in the areas of the brain they are responsible for.
Blurred vision is another common symptom of drunkenness. Alcohol seems to suppress the metabolism of glucose in the brain. The occipital lobe, the part of the brain responsible for receiving visual inputs, has been found to become especially impaired, consuming 29% less glucose than it should. With less glucose metabolism, it is thought that the cells aren’t able to process images properly.
Often, after much alcohol has been consumed, it is possible to experience vertigo, the sense that the room is spinning (sometimes referred to as ‘The Spins’). This is associated with abnormal eye movements. In this case, alcohol has affected the organs responsible for balance present in the ears. Balance in the body is monitored principally by two systems both of which are effected by alcohol sending abnormal impulses to the brain. The abnormal nerve impulses tell the brain that the body is rotating, causing disorientation and making the eyes spin round to compensate. When this wears off (usually taking until the following morning) the brain has adjusted to the spinning, and interprets not spinning as spinning in the opposite direction causing further disorientation. This is often a common symptom of the hangover.
Anterograde amnesia, colloquially referred to as “blacking out”, is another symptom of heavy drinking.
Another classic finding of alcohol intoxication is ataxia, in its appendicular, gait, and truncal forms. Appendicular ataxia results in jerky, uncoordinated movements of the limbs, as though each muscle were working independently from the others. Truncal ataxia results in postural instability; gait instability is manifested as a disorderly, wide-based gait with inconsistent foot positioning. Ataxia is responsible for the observation that drunk people are clumsy, sway back and forth, and often fall down. It is probably due to alcohol’s effect on the cerebellum.
Extreme overdoses can lead to alcohol poisoning and death due to respiratory depression.
A rare complication of acute alcohol ingestion is Wernicke’s encephalopathy, a disorder of thiamine (Vitamin B1) metabolism. If not treated with thiamine, Wernicke’s encephalopathy can progress to Korsakoff psychosis (degenerative Brain Disorder), which is irreversible.
Chronic alcohol ingestion over many years can severely damage specific parts of the brain responsible for coordinating gait; this can be observed as it produces the classic gait findings of alcohol intoxication even when its victim is not inebriated.