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Biology 202
2003 Second Web Paper
On Serendip

Looking Out for Future Pain

Luz Martinez


Pain is a method used by the body to interpret the outside world. Our skin is covered with sensory neurons that are responsible for acquiring information about the body's surroundings (6). Some of the nerve endings involved in the pain sensing process are called nociceptors (6). Most of the sensory receptors and nociceptors come from an area near the spinal cord (6). The information from the sensory neurons is sent through intermediate neurons and is passed onto the motor neurons that are involved in a physical movement, or are sent to the brain (1). In the brain, the information is interpreted and behavioral and emotional reactions are created (6). The definition of pain used by the International association for the Study of pain describes it as a sensory or emotional interpretation that is produced when there is the potential or actual occurrence of tissue damage (2).

Adults are able to verbalize the intensity of their pain and can help monitor the effectiveness of treatment when there is damage to the body tissue. How can adults interpret the pain in infants who cannot verbalize their experience? What concerns should we have when treating tissue damage in babies? What about the damage treatment of babies inside the womb?

It has been noted that a newborn has sensory nerve cells that have a greater respond rate than an adult (4). With sensitive sensory nerve cells, the spinal response to a stimulus is also increased and lasts for a longer period of time when compared with an adult (4). The appearance of these sensitive nerve cells is found on a larger portion of a newborn's skin when compared with adults (4). These sensory areas are called receptive fields (4). The receptive fields help the nervous system keep track of where the stimulus was received (4). With a larger receptive field, babies are unable to pin point the exact location of the stimulus (4).

Since newborns have very sensitive sensory nerves, the same response is produced to any stimulus without regard to the intensity (4). A newborn may react in the same way to a pinch as to a soft touch (4). The newborn will respond to non-harmful experiences as if they were potentially harmful (4).

Questions have been raised about the level of sensation that the fetus itself undergoes when using surgery to address abnormalities in a fetus (1). Surgery involves the opening of the mother's uterus to perform corrections on the fetus (1). Once corrected the fetus is returned to the mother's uterus to complete the normal term of development (1). The use of fetal surgery is a way of increasing the survival rate of the fetus after birth (1). The organs corrected would have inevitably prevented the baby from living after birth (1). The corrected threatening abnormalities may produce effects such as respiration failure, neurological damage, and heart failure (1).

The development of the nervous system may help determine the level of neural activity that can be interpreted as pain. The fetus is able to respond with reflex motions as early as 7.5 to 14 weeks (3). Although at 16-35 weeks the fetus displays patterns of reflexes the spinal cord is not yet fully developed (3). Usually the responses observed are exaggerated (2). Although the fetus is able to respond to a stimulus, the fetus needs the cortex as well as memory to experience pain (2). With memory, the fetus may interpret the sensations as pain due to past experiences that would lead to anxiety (2). Lloyd-Thomas and Fitzgerald suggest that the exaggerated response helps the fetus react to stimuli that it is not yet able to synthesis and produce a direct response to (2). The fetus displays receptor systems that have not yet matured (2). Without memory, the fetus is unable to interpret the stimulus as pain, but the fetal nervous system does respond to protect from harmful tissue damage (2).

Although the fetus and a newborn may not feel pain an interest in the issue has been raised due to the observation of the long-term consequences on the body's pain systems. An injury experienced early in development may affect the response to pain in childhood as well as adulthood (4).

It has been observed in adults that when a sensory nerve has been injured the nociceptive system, or pain system is altered (5). The pain experienced should only last for a period of time, until the tissue damage is corrected (5). When there is tissue damage and the sensory neuron is damaged as a result, the nociceptor is no longer considered reliable. The pain system ignores the damaged nociceptor's signals of pain sent to the brain (4).

The only way that pain is sensed in the region where the injured nociceptor is located is by having a neighboring nerve cell that is still functional monitor the area (4). This area continues to be on pain alert and remains sensitive to touch even after the tissue damage has been corrected (4).

Some suggest that because the fetus may not necessarily feel pain, the sensory neurons are in danger of malfunctioning (4). The neurons may be permanently altered if surgery is performed without taking precautions to prevent damage from reoccurring in the sensory neurons (4). Disabling the nociceptors may result in the spreading of nerve terminals in healthy sensors, thereby altering the areas covered by the sensory nerve (4). The nervous system is left with an altered picture of what area the pain is coming from (4). Oversensitive areas may develop as a result of alteration (4). These areas may be triggered by damage that will remain sensitive even though the damage is gone (4).

The sensation of pain is a system that incorporates physical sensation as well as past experiences. The experience of pain through emotions may affect how well a person can function in daily life. Considering ways to prevent pain receptor damage in developing nervous systems may help avoid future pain. There is no better time to catch a problem than before it begins.

References

1)Annual Reviews Medicine, Fetal Surgery, By Flake Alan W. and Michael R. Harrison; 1995

2)British Medical Journal, For Debate: Reflex responses do not necessarily signify pain British Medical Journal; 1996 (28 September), By Lloyd-Thomas, Adrian R. and Maria Fitzgerald.

3)New England Journal Of Medicine, Pain and its Effect in the Human Neonate and Fetus. The New England Journal Of Medicine, Volume 317, Number 21: Pages 1321-1329, 19 November 1987. By K.J.S. Anand, M.B.B.S., D.Phil., And P.R. Hickey, M.D

4)Medical Research Council, , The Birth of Pain. MRC News (London) Summer 1998:20-23. By Fitzgerald M.

5)Richeimer Pain Medical Group, , Understanding Nocicieptive & Neuropathic Pain; December 2000.

6)The Association of the British Pharmaceutical Industry, The Anatomy of Pain.


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