Nervous System

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)