The brain appears to be the organ most sensitive to alcohol abuse with a potential risk of both short and long-term brain damage. Researchers report that brain damage is not only extremely common in alcoholics, but also occurs in moderate, social drinkers. They suggest mild brain damage is so common that it affects the performance of many (among others) police, politicians and bureaucrats.
Further evidence that even moderate drinking damages the brain comes from recent (2004) studies at Johns Hopkins University. The researchers found that middle aged and elderly moderate drinkers have measurably smaller brains compared to nondrinkers.
The eye is another organ affected by alcohol. Using ophthalmoscopes to study conjunctival capillaries of the human eye, Melvin Knisely and his coworkers back in the 1960s first observed evidence of blood thickening at blood-alcohol concentrations as low as 0.025 per cent (after one drink). The researchers suggested blood thickening, even in social drinkers, may be sufficient to block fine blood pathways in the brain and cause brain damage.
Alcohol's inhibition of brain activity also affects vision. At a blood-alcohol concentration of around 0.08 per cent, the eyes' ability to focus is disturbed to such an extent that depth vision is impeded and double vision may occur. There is also evidence higher blood alcohol levels may be risk factors in night blindness and cataracts. The ear is also affected by alcohol. An estimated one in 10 Australians have impaired hearing. In Australia there are almost 10,000 workers compensation cases for industrial deafness every year. Alcohol may have played a significant role in many of these cases.
One of the protective mechanisms provided by nature against loud sounds involves an aural reflex action (similar to squinting eyes in sudden bright light), which tenses the eardrum and stiffens the lever action of the delicate bones in the ear, thus reducing the amplification of vibrations by up to 20 dB.
Alcohol can impair the reflex action of the autonomic nervous system by between 5 dB and 13 dB. This means drinkers are not protected from loud noises until the noise is much louder than usual. Drinking alcohol over the lunch hour thus makes workers more vulnerable to noise-induced hearing loss.
Alcohol drinking mixed with prolonged loud noise exposure such as at rock concerts, nightclubs or through personal stereos may be a major factor in the apparent increasing incidence of hearing loss observed in young adults.
Even at relatively low levels, such as after drinking a single drink, alcohol has been found to alter almost all membrane functions of nerve cells including neurotransmitter release, the functions of specific enzymes, ion-conductance channels, calcium-binding sites and signalling across membranes.
It is believed part of the mechanism that allows heavy drinkers to build up a "tolerance" to alcohol is found in the response of nerve cells, increasing the proportion of saturated fatty acids in the membranes to reduce the damaging effect of alcohol on the nerve cells.
This functional tolerance is a prerequisite to developing physical dependence, where adaptation to alcohol by the central nervous system necessitates the presence of alcohol to maintain feedback systems controlling the balance of cell processes. The body cannot then function "normally" in the absence of alcohol and a craving for alcohol develops.
When alcohol is withheld, withdrawal symptoms occur, such as nausea, hallucinations, depressions, involuntary trembling and anxiety. One of the most critical withdrawal symptoms is delirium tremens, known colloquially as the DTs. DTs typically involve hallucinations, disorientation, misperceptions, very rapid heartbeat and high blood pressure. These last two symptoms highlight the fact that alcohol affects the heart.
When a drink of, say, whisky is consumed, the heart may beat faster and give a sensation of warmth as a result of increased blood flow to dilated blood vessels near the surface of the skin.
If a considerable amount of alcohol is consumed, the increased flow of blood to surface capillaries may become visible as bloodshot eyes. The short-term effects of a drink or two may also occur in what is known as "holiday heart syndrome," which manifests itself as temporary heartbeat irregularities caused by the effects of acetaldehyde in the circulatory system.
Habitual heavy drinking damages the heart muscle and blood vessels and leads to elevated blood pressure. It has been estimated alcohol is a causative factor in at least 50 per cent of the cases of congestive heart disease, the most common cause of death associated with alcohol abuse.
For RSA certificate courses and RSA training, learn the responsible service of alcohol from South Bank Institute of Technology.
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