Wikijunior:Human Body/Pain

What is pain?

A man that inflects because he feels pain in his belly.

Pain is an unpleasant physical sensation. It is often caused by stimuli that are damaging or might be damaging if they are applied for a longer period of time. Pain is perceived differently from person to person and has a strong influence on their mood. Pain is often a sign of injury or disease. Usually pain resolves when the cause of it disappears.^[1]

Here you will find a lot about pain sensation. But remember, this is not a professional page, but rather an outline.

What is the function of pain?

Pain is very distressing but also has several functions, such as making you realize that something might be wrong with your body. Imagine that you prick your finger with a thorn of a rose. When you feel the pain you quickly withdraw your hand from the rose. Later, when you want to drink, you will take great care of your hurting finger and watch out that you do not touch the glass with it. This is how pain can protect us from damage.

How do we perceive pain?

Graphical illustration of pain sensation.

In and on your body, you have very tiny sensors that are called nociceptors. They are so small that you cannot see them by eye. Heat, chemicals and pressure can activate these sensors and make you perceive pain. When you hurt yourself, these sensors are switched on and send a signal to the opposite side of your brain. The signal is transmitted to the brain via nerve cells, also called neurons. Neurons are like very thin wires that connect different parts of the body so that these parts can communicate with each other.

Only when the signal has reached your brain you can interpret it and realize that you feel pain. However, this happens so quickly that it seems instantly to you. Often, your brain directly responds to pain with a reflex action such as the withdrawing of your hand from the rose.^[2]

Which organ systems are related to pain?

The pain-sensing nociceptors are found all over your body. You have many of them in your skin, in your muscles but also in your organs. Like this, you can feel pain in every part of your body.

All of these sensors are then linked to these very thin wires, the neurons. These wires then send the pain signal through the spinal cord, the highway of the neurons, to the brain.^[2]

Why do you rub the places that hurt?

What do you do when you hit your knee on a chair? You touch your knee and you rub it, don’t you? Some scientists believe that we rub the hurting body part to reduce the pain. They call this “gate control theory of pain”.

This theory is quite complicated. However, to get an idea of it, imagine again the wires called neurons. There are wires that send pain and others that send the rubbing sensation to the brain. These wires reach the brain via the spinal cord. At some point, both wires meet and pass through a place, which you can think of as a gate. This gate has a certain width that decides which signals can go through. If there is only the pain signal, without the rubbing, the gate will let all of the pain through. However, if you also rub your knee, the gate will let the rubbing signal pass but only part of the pain signal. That is why you reduce the pain if you rub your injured body part.^[3]

Where does phantom pain come from?

When someone loses a limb through an accident, they sometimes feel pain as if it were in the missing limb. This is called “phantom pain sensation”. How does this happen? One theory explains these sensations by the reorganization of the pain perceiving area in the brain.

Drawing of the Primary Somatosensory Cortex, showing the specific regions for pain perception of different body parts.

In your brain there is a specific part that interprets the signal of different sensations, such as pressure, touch and also pain. This so-called primary somatosensory cortex is the receiver of the pain neurons. Within the somatosensory cortex there are different regions responsible for sensing pain in every part of your body. There is a region that perceives pain from your hand, another one pain from your belly and so on. If someone lost their hand, the region that perceived pain from that hand would be taken over by another part of the body, for example the mouth. So, this person would think their hand is hurting when they feel something close to their mouth.^[4]

How can you prevent pain?

To prevent pain you should be careful while you are playing or doing sports, so you don’t hurt yourself. You should dress according to the weather to prevent getting a cold and hence a sore throat or other hurting symptoms. You should drink enough water to prevent headaches. You should live healthy to stay with good health and prevent pain from diseases. To live a healthy life you should eat healthy food and do enough physical activity.

References

↑ Definition of pain and distress and reporting requirements for laboratory animals: proceedings of the workshop held June 22, 2000. (National Academy Press, 2000)
↑ ^a ^b Pain and disability: clinical, behavioral, and public policy perspectives. (National Academy Press, 1987).
↑ Melzack, R. Gate control theory. Pain Forum 5, 128–138 (1996)
↑ Karl, A., Birbaumer, N., Lutzenberger, W., Cohen, L. G. & Flor, H. Reorganization of motor and somatosensory cortex in upper extremity amputees with phantom limb pain. J. Neurosci. Off. J. Soc. Neurosci. 21, 3609–3618 (2001).

[1] Definition of pain and distress and reporting requirements for laboratory animals: proceedings of the workshop held June 22, 2000. (National Academy Press, 2000)

[:0-2] Pain and disability: clinical, behavioral, and public policy perspectives. (National Academy Press, 1987).

[3] Melzack, R. Gate control theory. Pain Forum 5, 128–138 (1996)

[4] Karl, A., Birbaumer, N., Lutzenberger, W., Cohen, L. G. & Flor, H. Reorganization of motor and somatosensory cortex in upper extremity amputees with phantom limb pain. J. Neurosci. Off. J. Soc. Neurosci. 21, 3609–3618 (2001).

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