Alcohol consumption effects on the nervous system (II)
The action potential is
generated by the ionic channels and pumps located
on the cellular membrane. The ionic channels are
cellular molecular proteins that form pores on
the cellular membrane, and adjust the electronic
flow of different ions such as: sodium (Na+),
potassium (K+), calcium (Ca++) or chlorine (Cl-)
when the pores open and close. Each ionic channel
is selective and allows only one type of ion to
travel across. The ionic pumps maintain a normal
balance between different types of ions assigning
them on both sides of the cellular membrane.
In the majority of cases, the
nervous impulse is transmitted by the neurotransmitters.
Once the nervous impulse reaches the synaptic
terminations of the axons, it stimulates the synaptic
vesicles. A synaptic vesicle is a
spheric or irregular structures that contains
neurotransmitters and released them when the
synaptic vesicle is stimulated.
The molecules of the released
neurotransmitters spread out in the synaptic slit
and combine with neuroreceptor molecules from
synaptic membrane. Once the neurotransmitter is
released and spread along the synaptic
slit, it acts instantly.
There are two main mechanims that cause the
neurotransmitter to act fast:
a) instant reabsorption of the
neurotransmitter at synaptic level (the
neurotransmitter is assimilated by the synaptic
terminations which released it, stoping the
neurotransmitter to act)
b) chemical degradation of the
neurotransmitter (the neurotransmitter is
destroyed by the enzymes of the receptor).
There is a lock-and-key type relation between
the neurotransmitter and neuroreceptor molecules.
When these two molecules come together, they
modify the permeability of the receptor neuron's
membrane. Some neurotrasmitters can increase the
membrane permeability through a process called
depolarization, while others decrease its
permeability having a inhibitor effect.
The transmission speed of the action potential
through dendrites to axon fluctuates between 3
and 320 km per hour. This speed fluctuation is
caused by the axon's diameter (bigger diameter
axons transmit the action potential faster) and
by the presents or abstance of myelin sheath
(because the myelin functions as an isolator, it
causes the impulse to move forward by leaps
increasing the speed of the action potential).
The medical condition caused by impaired myelin
layers are impaired is called multiple sclerosis.
Multiple sclerosis is characterized by severe
dysfunctions of the motor and sensorial nerves.
Up to now, there are known over 50 neurotransmitters
and this number will grow in the near future.
There are neurotransmitters with two different
types of receptor molecules. Some can have an
aroused effect in some areas of the nervous
system and an inhibitor effect in others.
The most important neurotrasmitters are:
Acetylcholine (ACh) is a
neurotransmitter that can be found in many
synapses and, in general, has an arousal effect.
It can also have an inhibitory effect. The effect
of the acetylcholine depends on the types of the
receptor molecules found in the membrane of the
receptor neuron. This neurotransmitter is found
especially in hypocamp, a cerebral structure that
plays an important role when new memories are
formed. Those cells that produce acetylcholine
tend to degenerate in Alzheimer patients causing
a decreased amount of acetylcholine. A
lower-than-normal amount of ACh causes a sevete
loss of memory. Some drugs that reduce the amount
of acetylcholine produced cause muscular
Norepinephrine (NE) is a
neurotransmitter mostly produced by the neurons
of the cerebral trunk.
Two well-known drugs, cocaine and amphetamines,
extend the action of NE and slow down the
reabsorption processes because the receptor
neurons are activated longer than normal. This
explains why cocain and amphetamine have
psycho-stimulanting effects. By contrast, lithium
cause an inverse process leading to depressive
Gamma-aminobutyric acid (GABA) is
one of the major inhibitors of the nervous
When the substance called pycrotoxine blocks the
GABA receptors, the muscular movement connot be
controled and the person displays convulsions.
Recent researches suggested that the alcohol
inhibits the glutamate system stimulating the
neurons, and activates the GABA system.
Two other substances that modify the moods by
increasing or decreasing the neurotransmitter
concentration are chlorpromazine
and LSD. The chlorpromazine is a
drug used in the treatment of schizophrenia, and
it blocks the dopamine's receptors. A dopamine
excess at synaptic level is found in
schizophrenia and a dompamine restraint is found
inParkinson disease. LSD has a similar chemical
structure with serotonin - a substance that
influences the emotions. Medical researches
suggest that LSD accumulates in specific cerebral
cells and imitates the serotonin.
Glutamate is a excitatory
neurotransmitter that can be found in the neurons
from the central nervous system. There are at
least three types of glutamate receptors, one of
them (the NMDA receptor) is playing an important
role in learning and memorizing process. An
increased number of NMDA receptors are located
near the center of the brain. According to some
medical trials, this brain area plays an
important role in building new memories.
The alcohol progressively influences the
central nervous system's function.
When a person start to drink excessively, the
alcohol affects the cerebral hemispheres
which represent the center of the conscienceness,
reasoning and the central place where senzorial
information arrive. When there is a 0,3-0,5%o
alcohol blood concentration, the person
experiences light dizziness, a relaxation
feeling, and a light euphoria. People say things
that usually they would not say, tend to become
more communicative and sociable, and become less
critical while their good mood increases. Their
self-esteem increases while their motor reaction
decrease. The intellectual efficaciousness also
decreases, but the drinker over-estimates its
efficaciousness. The person tends to take wrong
and risky decisions because he/she don't assess
correctly the potential danger and difficulties.
When the alcohol concetration increases to
1-2%o, the cerebellum is
paralysed and the sensorial and motor functins
are seriously impaired. Some people tend either
to behave aggressively and get upset easely, or
are quite and grouchy. They speak slow and have
difficulties in coordonating their movements
(cannot maintain the body's equilibrium). This
explains why poeple in an advanced state of
intoxication stagger, do not find the key hole
When the alcohol concentration reaches 2-3%o,
the medulla is anaesthetized.
Meddula controls the reflexes of unconscious
movements and the normal functioning of internal
organs like urine bladder and rectum. The alcohol
progressively causes a slow rate of reflexes
activation until these reflexes numb and the
bladder and intestin sphincters cannot be
At an advanced state of intoxication (higher
than 3-4%o), the cerebral trunk
is paralyzed. This causes a slow breathing rhythm
that can lead to a heart failure and even death.
Silly bets, where drinking a bottle of strong
liquor is considered a masculinity proof, lead to
a high alcohol concentrations in the blood
causing a serious alcohol intoxication and can be
followed by death.
Unfortunately, an alcoholic does not pay
attention to all these severe repercussions when
he/she drinks. He/she only wants to release the
interior tension and to relax, to change his/her
mood, and achieve a better mood and to stop
carring about porblems. However, in order to
achieve all these, the alcoholic is paying the
price of impairing his/her vital cerebral
functions. In time his/her problems worsen and
cannot be solved. When the mind is controlled by
the alcohol's vapors, the alcoholic do not solves
problems, but he/she is lossing those needed
functions and abilities that can help him/her to
find answers and solutions.
The information presented above show
how thoughtless an acoholic acts paying for his
"interior peace" the price of lossing
his/her body normal function and nevetheless the
normal functions of the brain.