Nervous
System
Our
perception of the world and our interaction with our surroundings depend on the
functions or physiology of the nervous system. Most activities of the nervous
system start when sensory receptors (visual receptors of the eyes, auditory
receptors in the ears, tactile receptors in the surface of our body, etc.) are
excited when sensing certain stimuli. When these receptors catch and external
factor, it is called a “sensory experience”. In a matter of milliseconds, these
receptors send an electric impulse to the brain and the brain “activates” the
sensation our body feels when stimulated by that certain factor. This is how we
feel pain. And as very few are aware of, it is a very complicated process. (www.nlm.nih.gov).
For
example, when we suffer a little paper-cut, the tactile receptors of the skin
are activated, sending a signal to our brain and the brain creates the feeling
or sensation we perceive as pain. Also, each different stimulus is received and
process by and specific brain lobe. The occipital lobe receives and processes
visual information, the temporal lobe receives auditory signals (such as language
and meaning of words) and the parietal lobe is associated with the sensory
cortex, and is associated with feelings about touch, heat, pain, etc.
The nervous system is divided
between the central nervous system (CNS) and the peripheral nervous system
(PNS). In the central nervous system we find the encephalon and the spinal
cord. The encephalon is formed by the well known brain and also by the
cerebellum and the brainstem. The brainstem contains the thalamus, the
hypothalamus, the mesencephalon and other structures that connect the
encephalon with the spinal cord.
The peripheral nervous system
connects the CNS with other parts of the body and is composed by nerves
(bundles of neurons). The PNS is divided into two: the sympathetic and
parasympathetic. The roles that each one of them perform in our body are better
explained with and example. The sympathetic system activates the peristaltic
movements when we have ingested food and the parasympathetic system stops these
movements when they are no longer needed.
The nervous system is conformed by
two types of matters. Gray matter receives impulses and information so it is in
the center of the brain and the cerebellum but in the outer part of the spinal
cord to receive signals sent by, for example, nerves in the skin. The other
matter, white matter, sends impulses and information. It is located in the
outer part of the brain and the cerebellum and in the inner part of the spinal
cord.
When we are injured, the nerves in
the damaged tissue send signals to the gray matter in the spinal cord and the
white matter of the spinal cord sends these impulses to the brainstem. In the
brainstem, as mentioned before, is the thalamus. The thalamus is the center of
pain in the whole nervous system, and it traduces this information into pain.
The signal goes all the way back to the tissue nerves and that is when we
actually begin feeling it. The most extraordinary part of this is the velocity
of this sensation. As everyone is aware of, the sensation of pain appears
practically at the same time as the injury is made. (www.nlm.nih.gov).
Pain
Categorization
and diagnosis
Pain,
as explained before, is a feeling triggered by our nervous system, warning us
that tissue damage has occurred or may be occurring. Besides the suffering we
feel when feeling it, pain is very helpful. It causes withdrawal from damaging
or dangerous situations, such as removing a finger quickly form burning water,
or it is a way the human body warns the patient of an inner problem.
But,
of course, pain is also a negative feeling. In the United Sates, the feeling of
pain is the main reason for physician consultation. Also, pain interferes with
the person´s quality of life and general functioning.
CIPA
Pain,
specially localized pain, is very important at the time of diagnosing a
patient, because pain is often caused by damaging stimuli, sometimes inside our
body. Without pain, doctors would not be able to detect some serious conditions
or diseases, like cancer. CIPA or “Congenital Insensitivity to Pain with
Anhidrosis” is a very rare disease which causes the loss of the feeling of
pain. “Patients with this disorder
are very likely to injure themselves in ways that would normally be prevented
by feeling pain” (Wikipedia.org). People suffering this disease tend to
live 25 years maximum, because they lack the benefits pain actually has. For
example, if a person falls down from a tree, the pain he/she feels will be
remembered every time the person wants to climb a tree again, so he/she would
be more precautious, but a patient with CIPA could not feel the pain, so this
person could die after suffering a fatal fall, because he/she never understands
the danger it represents. (Wikipedia.org).
Patients
with CIPA often suffer from infections, broken bones, in arms, legs and oral
structures, etc. Besides this injures caused by accidents, these people suffer
from hyperthermia, which is a high temperature that exceeds the normal levels.
This hyperthermia is due to the inability to sweat in these patients. Often
hyperthermia burns neurons causing mental retardation. (Wikipedia.org). This
overheating causes half of the CIPA patients under the three years to die. They
also have ocular problems because they scratch too much their eyes, unaware of
the damage they are causing themselves and they even injure them while during
their sleep. (Wikipedia.org). It is even recommended for parents of CIPA babies
to remove the teeth from their infants because they may bite through their
lips, tongue and even their finger. (A human could cut his/her finger out as
easily as biting a carrot but the awareness of the pain we will feel and self
preservation stops us). Finally, the patient´s vital signs need to be
periodically checked because the patient can’t feel when something is wrong. (Wikipedia.org).
CIPA
is caused because of a genetic mutation. This mutation restrains the formation
of a specific type of nerves (gene NTRK1) that are responsible for transmitting
signals of pain, heat and cold to the brain. Researchers have not being able to
find any relation of this disease with any specific ethnic group, but there
appears to be a certain higher possibility of having CIPA when you belong to a
culture where intermarriage is accepted (Wikipedia.org).
Treatments
are not always efficient that there has been some success with a treatment
using Naloxone. This is a chemical that blocks the nervous system from causing
the inactions that occur when a patient should feel pain, heat, or cold. (Wikipedia.org).This,
though, is not enough because CIPA patients often suffer from other conditions,
like the absence of a sweat gland. CIPA is extremely rare. There are just 84
documented cases living in the United States. In 1963 CIPA was first listed as
a disorder, and by that time only sixty cases had been documented.
(Wikipedia.org).
Categorization
According
to medicinal articles, pain can be separated into three different categories
regarding its mechanisms: Nociceptive pain, neuropathic pain, and psychogenic
pain. (www.seattlepi.com).
Nociceptive
pain is caused by an ongoing activation of external or internal body tissues.
When the pain is external, it is called “somatic pain”, as when having a
bruise. And when the pain is internal, it is called a “visceral pain”, like
when suffering and inner bleeding. (www.seattlepi.com).
Neuropathic pain occurs by changes in the
nervous system that alter it in a way that the pain is sustained after an
injury has already healed. (www.seattlepi.com).
Finally,
psychogenetic pain is an “imaginary” pain. The patient does feel the pain, but
it has no reasonable reason of being. It is commonly associated with other psychological
diseases that create the pain. There are even cases of imaginary pain where
drug addicts feel pain and they justify their drug use with this inexistent
pain. (www.seattlepi.com).
Pain
is so broad and complex that it has also been categorized depending on its
characteristics. Regarding the intensity of pain, it has been categorized as
dull or sharp. Pain could be considered constant or brief because of its
lasting, too. Localized pain is very helpful for a diagnosis, but there could
also be a general pain, such as the muscular pain felt during flu. (www.seattlepi.com).
Another
way to classify pain is into “acute” and “chronic”. Acute pain lasts a short
period of time, or is expected to. On the other hand, chronic pain is a pain
that lasts beyond the healing of the injury, or is a symptom of and ongoing
incurable disease, such as cancer. (www.seattlepi.com).
Recently, scientists have generated the theory that pain, not all but
some of it, is a matter of the mind. They have concluded that “Key regions of
the brain appear to react as much to expectations and empathy as they do to
actual painful stimulation”. (www.seattlepi.com). Using this new findings, in the future we could be able to reduce
pain simply by meditating, or controlling pain with our minds.
How is pain
stopped?
In most cases, pain stops when the disease or injury
causing it has been healed or stopped.
Sometimes,
time is all that is needed for the pain to disappear, but it is not always that
simple. For example, simple diseases caused by a virus can’t be cured with
medicine, but will eventually fade away. For treating the pain of these
diseases, painkillers like analgesics or anesthetics. (http://www.emc.maricopa.edu)
Since mankind started performing
medical procedures, such as simple surgeries, ways to reduce pain have been
searched and discovered. This has been easy because pain depends on the brain.
If we are able to block the neural impulses from the brain, pain stops.
Procedures like massages or acupuncture have and incredible effect on pain
because they stimulate certain zones of the neural system, stopping the pain
signal of the brain, and also relaxing the body. (http://www.emc.maricopa.edu)
Pain can even be stopped using
“placebos”. A group of patients were given a simple effect-less saline
solution, or placebo, and were told that they were receiving morphine in order
to reduce the pain they were suffering. 35% of this people said that the pain
really stopped, which proves how powerful the mind is when it comes to stopping
pain. (http://www.emc.maricopa.edu)
Drugs, when used correctly, have a
great effect against pain because they block the signals arriving to the brain.
For example, opium and heroin, artificial chemicals, can have the same effect
that endorphins have in our body. Endorphins, natural opioids produced in the
body, produce elation and reduction of pain. Heroin is a derivative of
morphine, and it is usually injected intravenously. Snorting and smoking are
also valid methods of consuming it. Heroin binds the ophioid receptors of the
brain where endorphins usually stop the feeling of pain (http://www.emc.maricopa.edu)
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