Cerebral Cortex
The cerebral cortex is the highest portion of the
brain. The cortex processes information from your
senses, does your "thought" processing and
consciousness (in combination with a structure called
the basal ganglia), initiates most voluntary muscle
movements and influences lower-order brain centers.
In the cortex, alcohol does the following:
- Depresses the behavioral inhibitory centers - The person becomes more talkative, more self-confident and less socially inhibited.
- Slows down the processing of information from the senses - The person has trouble seeing, hearing, smelling, touching and tasting; also, the threshold for pain is raised.
- Inhibits thought processes - The person does not use good judgment or think clearly.
These effects get more pronounced as the
BAC
increases.
Limbic System
The limbic system consists of areas of the brain
called the hippocampus and septal area. The limbic
system controls emotions and memory. As alcohol
affects this system, the person is subject to
exaggerated states of emotion (anger, aggressiveness,
withdrawal) and memory loss.
Cerebellum
The cerebellum coordinates the movement of
muscles. The brain impulses that begin muscle
movement originate in the motor centers of the
cerebral cortex and travel through the medulla and
spinal cord to the muscles. As the nerve signals pass
through the medulla, they are influenced by nerve
impulses from the cerebellum. The cerebellum controls
fine movements. For example, you can normally touch
your finger to your nose in one smooth motion with
your eyes closed; if your cerebellum were not
functioning, the motion would be extremely shaky or
jerky. As alcohol affects the cerebellum, muscle
movements become uncoordinated.
In addition to coordinating voluntary muscle
movements, the cerebellum also coordinates the fine
muscle movements involved in maintaining your
balance. So, as alcohol affects the cerebellum, a
person loses his or her balance frequently. At this
stage, this person might be described as "falling
down drunk."
Hypothalamus and Pituitary Gland
The hypothalamus is an area of the brain that
controls and influences many automatic functions of
the brain through actions on the medulla, and
coordinates many chemical or endocrine functions
(secretions of sex, thyroid and growth hormones)
through chemical and nerve impulse actions on the
pituitary gland. Alcohol has two noticeable effects
on the hypothalamus and pituitary gland, which
influence sexual behavior and urinary excretion.
Alcohol depresses the nerve centers in the
hypothalamus that control sexual arousal and
performance. As BAC increases, sexual behavior
increases, but sexual performance declines. This
observation has been known for a long time, and is
referred to by William Shakespeare in "Macbeth" (Act
2 scene 3):
Macduff: What three things does drink
especially promote?
Porter: Marry sir, nose-painting, sleep, and
urine. Lechery, sir it provokes, and unprovokes; it
provokes the desire, but it takes away the
performance...
The porter in the above excerpt also notes the
effect of alcohol on urine excretion. Alcohol
inhibits the pituitary secretion of anti-diuretic
hormone (ADH), which acts on the kidney to reabsorb
water. Alcohol acts on the hypothalamus/pituitary to
reduce the circulating levels of ADH. When ADH levels
drop, the kidneys do not reabsorb as much water;
consequently, the kidneys produce more urine.
Medulla
The medulla, or brain stem, controls or influences
all of the bodily functions that you do not have to
think about, like breathing, heart rate, temperature
and consciousness. As alcohol starts to influence
upper centers in the medulla, such as the reticular
formation, a person will start to feel sleepy and may
eventually become unconscious as BAC increases. If
the BAC gets high enough to influence the breathing,
heart rate and temperature centers, a person will
breathe slowly or stop breathing altogether, and both
blood pressure and body temperature will fall. These
conditions can be fatal.
For more information on the parts of the brain and
their functions, see
Alcohol's Effects.
Alcohol's Effects on Other Body Systems
In addition to the brain, alcohol can affect other
body tissues. It has the following effects on other
systems in the body:
- Irritates the linings of the stomach and
intestine - This can lead to vomiting.
-
Increases blood flow to the stomach and intestines
- This increases secretions by these organs, most
notably stomach acid secretion.
-
Increases blood flow to the skin - This causes
a person to sweat and look flushed. The sweating
causes body heat to be lost, and the person's body
temperature may actually fall below normal.
-
Reduces blood flow to muscles - This can lead
to muscle aches, most notably when a person recovers
from the alcohol (the "hangover").
All of alcohol's effects continue until the
ingested alcohol is eliminated by the body.
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