Alcohol and the body
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What alcohol does to the body
Central nervous system depressant
Drinkers often perceive alcohol to be stimulating.
This perception, which usually occurs at lower levels of alcohol
intake, results from a depression of inhibitory
control mechanisms in the brain. Alcohol, like other general anesthetics,
is a primary and continuous depressant of the central nervous
system (CNS). First it destroys the integrating control of the
brain. Thought processes may be jumbled and disorganized; the
drinker may become confused. In addition, motor functions may
Uncontrolled mood swings
The first mental processes to be affected are
those that depend on training and experience. The finer grades
of discrimination, memory, judgment, concentration and insight
will be dulled, then lost.
Confidence may abound. Personality changes may
occur as well as uncontrolled mood swings. Emotional outbursts
may become frequent. The subject may suffer sensory and motor
disturbances. As intoxication progresses, general impairment of
nervous function and a condition of general anesthesia prevail.
Factors governing effect of alcohol
The effect of a given amount of alcohol on a
person is a function, among other things, of the rate at which
the alcohol is consumed, the BAC achieved, the subject's tolerance
to alcohol, and the setting (e.g., party atmosphere versus a more
The degree of impairment is dose related. However,
it is not identical or linear for all behaviors. It is clear that
behavioral skills requiring cognitive functioning suffer the greatest
impairment. Put another way, impairment of the cognitive functions
begins at lower levels than for simple tasks.
Tolerance will develop in regular drinkers, but
not necessarily uniformly for all behavioral skills. Motor co-ordination
shows the most tolerance. Whether tolerance develops with respect
to complex skills and cognitive functioning is unclear.
Impairment of divided attention skills (performance
of two or more tasks) shows little evidence of tolerance, whereas
some short-term memory studies suggest that it may develop for
complex tasks, as well as simple ones.
More alcohol needed to achieve same effect
Tolerance to many effects of alcohol is easily
Alcohol is metabolized by the liver. A person
who uses alcohol wants the desired effect to last as long as possible.
Alcohol metabolism or transformation limits its duration of action.
Repeated exposure of the metabolizing system
(mainly the liver) to alcohol increases the system's capability
and efficiency. As a result, the alcohol is metabolized more quickly
and the duration and intensity of the desired effect are considerably
reduced. This is called metabolic tolerance.
To regain the desired effect of the alcohol,
the individual must increase the dosage and/or frequency of consumption.
Central nervous system tolerance
CNS tolerance occurs when cells adapt to the
presence of alcohol so as to diminish the effect on them of a
given level of alcohol. This tolerance does not develop at the
same rate for all effects and may not develop at all for others.
This is called functional tolerance. As with metabolic tolerance,
the user increases the dose and/or frequency of administration
to overcome this tolerance, reinstating or enhancing the desired
Loss of tolerance
As with drugs, tolerance to alcohol, once developed,
will lessen with time if alcohol is no longer taken regularly.
Generally, if drinking stops, the person's body will revert to
the tolerance level in existence when alcohol was consumed for
the first time. If, after a long period of abstinence, alcohol
consumption again becomes regular, there is considerable evidence
to suggest the former tolerance is acquired more quickly.
Impairment versus intoxication
It should be noted that individuals can be impaired
by alcohol without displaying any outward signs. Impairment is
not simply the appearance of gross physical symptoms but it is
also a deterioration of judgment, attention, loss of fine co-ordination
and control with a possible increase in reaction time and a diminishing
of sensory perception.
Intoxication is an advanced state of impairment
in which the gross physical symptoms of the effects of alcohol
are apparent. The point at which "impairment" becomes "intoxication"
is unique to the subject and depends on tolerance.
Impairment and rising or falling BAC
Studies have shown that impairment is greater
at a given blood alcohol level when BAC is increasing than for
the same BAC when the blood alcohol level is falling. This is
called the Mellanby effect.
The manner of consumption also can affect impairment.
If alcohol is consumed at a slow and steady pace, it is likely
that there will be a slow and steady increase in impairment. If
the alcohol is consumed more quickly, the rate of increase in
impairment may also be more rapid and appear at lower BACs.
If alcohol is consumed quickly (bolus drinking),
the rate of performance deficit may be further accelerated because
the alcohol is absorbed into the blood stream more rapidly. The
increasing impairment is generally obvious to the observer due
to the greater than expected rate of deterioration in abilities
Tolerance developed to a given BAC achieved in
social drinking, may not help to moderate the effects of alcohol
when the same BAC is achieved by bolus consumption.
Disclaimer: The material on this site is not intended as legal advice. It merely conveys general information on legal issues commonly encountered by persons facing criminal charges in Canada. If you are charged with an offence, you should contact a criminal lawyer.