The World Health Organization (WHO)
recommends "low to moderate alcohol intake"
to reduce risk of coronary heart disease
. Also it has been suggested that
moderate consumption of alcohol can reduce
the risk of dementia, facilitate memory and
learning, and even improve IQ scores . Moderate drinkers tend to have better
health and live longer than those who
abstain from alcohol or are heavy drinkers.
Effects by dose
Different concentrations of alcohol in the
human body have different effects on the
subject. The following lists the effects of
alcohol on the body, depending on the blood
alcohol concentration or BAC.
Please note: the BAC percentages provided
below are just estimates and used for
illustrative purposes only. They are not
meant to be an exhaustive reference; please
refer to a healthcare professional if more
information is needed.
Euphoria (BAC = 0.03 to 0.12 %)
Subject may experience an overall
improvement in mood and possible euphoria.
They may become more self-confident or
daring.
Their attention span shortens. They may look
flushed.
Their judgement is not as good — they may
express the first thought that comes to
mind, rather than an appropriate comment for
the given situation.
They have trouble with fine movements, such
as writing or signing their name.
Lethargy (BAC = 0.09 to 0.25 %)
Subject may become sleepy
They have trouble understanding or
remembering things (even recent events).
They do not react to situations as quickly
(if they spill a drink they may just stare
at it).
Their body movements are uncoordinated; they
begin to lose their balance easily.
Their vision becomes blurry. They may have
trouble sensing things (hearing, tasting,
feeling, etc.).
Confusion (BAC = 0.18 to 0.30 %)
Profound confusion — uncertain where they
are or what they are doing. Dizziness and
staggering occur.
Heightened emotional state — aggressive,
withdrawn, or overly affectionate. Vision,
speech, and awareness are impaired.
Poor coordination and pain response. Nausea
and vomiting often occur.
Stupor (BAC = 0.25 to 0.40 %)
Movement severely impaired; lapses in and
out of consciousness.
Subjects can slip into a coma; will become
completely unaware of surroundings, time
passage, and actions.
Risk of death is very high due to alcohol
poisoning and/or pulmonary aspiration of
vomit while unconscious.
Coma (BAC = 0.35 to 0.50 %)
Unconsciousness sets in.
Reflexes are depressed (i.e., pupils do not
respond appropriately to changes in light).
Breathing is slower and more shallow. Heart
rate drops. Death usually occurs at levels
in this range.
Death (BAC more than 0.50 %)
Alcohol causes Central Nervous System to
fail, resulting in death.
Moderate doses
Although alcohol is typically thought of
purely as a depressant, at low
concentrations it can actually stimulate
certain areas of the brain. Alcohol
sensitises the N-methyl-D-aspartate (NMDA)
system of the brain, making it more
receptive to the neurotransmitter glutamate.
Stimulated areas include the cortex,
hippocampus and nucleus accumbens, which are
responsible for thinking and pleasure
seeking. Another one of alcohol's agreeable
effects is body relaxation, possibly caused
by heightened alpha brain waves surging
across the brain. Alpha waves are observed
(with the aid of EEGs) when the body is
relaxed. Heightened pulses are thought to
correspond to higher levels of enjoyment.
A well-known side effect of alcohol is
lowering inhibitions. Areas of the brain
responsible for planning and motor learning
are dulled. A related effect, caused by even
low levels of alcohol, is the tendency for
people to become more animated in speech and
movement. This is due to increased
metabolism in areas of the brain associated
with movement, such as the nigrostriatal
pathway. This causes reward systems in the
brain to become more active, and combined
with reduced understanding of the
consequences of their behavior, can induce
people to behave in an uncharacteristically
loud and cheerful manner.
Behavioural changes associated with
drunkenness are, to some degree, contextual.
A scientific study found that people
drinking in a social setting significantly
and dramatically altered their behaviour
immediately after the first sip of alcohol,
well before the chemical itself could have
filtered through to the nervous system.
Likewise, people consuming non-alcoholic
drinks often exhibit drunk-like behaviour on
a par with their alcohol-drinking companions
even though their own drinks contained no
alcohol whatsoever.
Excessive doses
The effect alcohol has on the NMDA
receptors, earlier responsible for
pleasurable stimulation, turns from a
blessing to a curse if too much alcohol is
consumed. NMDA receptors start to become
unresponsive, slowing thought in the areas
of the brain they are responsible for.
Contributing to this effect is the activity
which alcohol induces in the gamma-aminobutyric
acid system (GABA). The GABA system is known
to inhibit activity in the brain. GABA could
also be responsible for the memory
impairment that many people experience. It
has been asserted that GABA signals
interfere with the registration and
consolidation stages of memory formation. As
the GABA system is found in the hippocampus,
(among other areas in the CNS), which is
thought to play a large role in memory
formation, this is thought to be possible.
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 (referred to
in certain circles as 'The Spins'). This is
associated with abnormal eye movements
called nystagmus, specifically positional
alcohol nystagmus. In this case, alcohol has
affected the organs responsible for balance
(vestibular system), present in the ears.
Balance in the body is monitored principally
by two systems: the semicircular canals, and
the utricle and saccule pair. Inside both of
these is a flexible blob called a cupula,
which moves when the body moves. This
brushes against hairs in the ear, creating
nerve impulses that travel through the
vestibulocochlear nerve (Cranial nerve VIII)
in to the brain. However, when alcohol gets
in to the bloodstream it distorts the shape
of the cupola, causing it to keep pressing
on to the hairs. 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.
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 encephalopathy, a
disorder of thiamine metabolism. If not
treated with thiamine, Wernicke
encephalopathy can progress to Korsakoff
psychosis, which is irreversible.
Chronic alcohol ingestion over many years
can produce atrophy of the vermis, which is
the part of the cerebellum responsible for
coordinating gait; vermian atrophy produces
the classic gait findings of alcohol
intoxication even when its victim is not
inebriated.
Severe drunkenness and diabetic coma can be
mistaken for each other on casual
inspection, with potentially serious medical
consequences for diabetics. The major
physical finding they share is the
sickly-sweet odour of ketosis on the breath;
alcoholic ketosis and diabetic ketosis are
both marked by the presence of acetone and
other ketones in the bloodstream, although
the ketones are produced by different
metabolic pathways in each disorder.
Measurement of the serum glucose and ethanol
concentrations in comatose individuals is
Ethanol routinely performed in the emergency
department and easily distinguishes the two
conditions.
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