Alcohol consumption effects on the nervous system (I)
In order to understand the
complexed phenomena that take place at the
central nervous system's level,
let's look over its structural schema.
For a better understanding and
with a didactic purpose, I decide to present the
nervous system in two, main categories which are
also devided in two subcategories.
Central nervous system contains
the brain and the spinal cord.
Peripheral nervous system consists
the nerves that connect different areas of the
brains to the spinal cord and different body
The somatic nervous system colects
information from the tegument and muscle
receptors about the external stimuli and send
them to the central nervous system (this explains
why we feel pain, physical pressure and
temperature variation). The somatic nervous
system motor nerves send the impulses from the
central nervous system to the muscles causing the
voluntary movement, and allows the body to
maintain its equilibrium and adjust its posture.
Vegetative nervous system sends
the nervous impulses from or to the internal
organs, controlling the breathing and digestive
process, and cardiac activity.
The human brain consist in 3 concentric layers:
The internal layer contains:
rachidian bulb that controls the breathing
process and postural reflexes; cerebellum that
controls the motor activity; thalamus - the relay
station of the sensorial information that comes
from the sensorial level; hypothalamus,that plays
an important role in controling the emotions and
homeostasis: and reticular system, which crosses
some of the structures mentioned above, and
controls the wakefulness state and body
The limbic system together with
the hypothalamus controls some of the instinctual
activities such as feeding, aggression, running
from danger, and choosing the sexual partner;
This nervous structure plays also an important
role in the memory and attention process.
The external layer called the
cerebral cortex is formed from two cerebral
hemispheres. It plays a significant role in
several processes like sensorial, decision
taking, learning and thinking process. The cortex
contains the central centers of the analyzators
and association areas, and controls the specific
The base unit of the nervous system is a
specialized cell called the neuron.
The neuron body is formed from
short extensions called dendrites
and a long, unique extension called axon.
When the dendrites or neuronal body is
stimulated, a nervous impulse forms which is send
out through the axon. The sensitive neurons send
the received signals from the sensory organs to
the cerebral segments of the nervous system,
while the motor neurons send out the signals from
the nervous system to the muscles and endocrine
A nerve is formed from the
axonal fibers of hundreds or even thousands of
neurons, and contains sensitive and motor fibers.
At the neuron level, the information is send
out in one direction as a biochemical impulse
(called nervous impulse or action
potential) from the dendrites to the end
of the axon. The action potential is caused by a
self-programmed mechanism called depolarization.
According to this mechanism, the cellular
membrane permeability changes for different types
of ions (atoms or electrical molecule) that enter
and leave the cell.