How are Signals of Pain 'Transmitted'?
Most illnesses leas to damage of the body. It can be joints, muscle, bones, inner organs or nerves that are damaged and precisely this damage is experienced as pain. How you feel the pain depends on the damage (what is damaged and to what extent) and personal conditions like culture, habit and psychological conditions. In the cases, where it is not possible to prove that the body has been damaged, you do not know why the pain arises.
Acute pain
We all have pain sensors in skin, muscle, heart, bones vessels and inner organs. The pain sensors register harmful effects on the body like for example blows, pushes, heat and cold. When the pain sensors detect a harmful effect they transmit a signal through our nerve fibres (the power cables) to the spinal cord and hereafter to the brain – it happens the same way power runs from the switch through the wire to the light bulb in a lamp. The nerve fibres vary in size from very fine threads to the very big sciatic nerve in the thigh that has size of a little finger. In the brain the signal is recoded into an experience of pain.
From acute to chronic pain
If you for example hold the finger on a hot plate, the pain sensors in the skin register that the tissue is damaged by the heat. The nerve fibres transmit the signal from the pain sensors on to the brain where the signal is recoded into pain. Sensibly, you therefore remove your finger from the hot plate. So, the pain is a signal to you that you should be aware that something in your body is being damaged. In that way, acute pain protects your body.
However, it is far from always that simple. In the case of a sprained joint, a fractured bone or menstrual pain you cannot just avoid the damage – it has already happened. In those cases, there is a need for painkilling medication, ice bags, elastic bandage for the foot or a cast around the fracture.
Under normal circumstances, our pain sensors are asleep and it takes a powerful effect for them to wake up and transmit a signal to the brain about the presence of pain. However, if our body is exposed to prolonged or repeated damaging effect the pain sensors become hypersensitive and react to very small painful effects. This means that you experience pain without it being a sign of an actual harmful effect to the body. This hypersensitivity in the pain sensors is seen with many with chronic pain – for example patients with rheumatic diseases.
In other cases, the spinal cord transmits a signal to the brain about the presence of pain even though the pain sensors are not affected at all. As an example, chronic back pain can be mentioned where numerous examinations have been unable to prove any cause for the pain – everything is normal. It is well-known that there is no certain connection between demonstrable harmful changes in the body and the occurrence of chronic pain. Some patients can be pervasively ill without pain while others can be tormented by pain without signs of pervasive illness. Typical chronic pains are back pains, headache, arthritis pain, adhesions in the stomach, chronic inflammation in the pancreas or gall bladder.
Cancerous pain
When a malignant tumour grows, it pulls and pushes the surrounding normal tissue. A tumour in the colon – as it grows – pushes the surrounding normal intestine. In the case of the tumour spreading to for example the brain, it pushes and damages the surrounding normal brain tissue. The pain sensors detect this, transmit signals to the brain and pain is experienced. Typically, this concerns pressure to inner organs or pressure to bones (tissue pain) or damage to nerve tissue (nerve pain).
A part – of those who have had cancer – have pain following the treatment (surgery, chemotherapy or radiation treatment) that is administered to reduce or remove the tumour – in that case, a side-effect to the very treatment of the cancer. The pain arises because the treatment leads to damage of the body – chemotherapy and radiation treatment do not only affect the cancer cells but also the surrounding normal tissue.