What Is Pain?
Pain can be described as a sensation with causes discomfort, and perhaps agony. It may be constant or a throbbing pain.
Pain which originates from the nervous system is called non-nociceptive because there are no specific pain receptors. Nociceptive means responding to pain. When a nerve is injured it becomes unstable thus its signalling system becomes muddled. The brain interprets these abnormal signals as pain. This randomness can also cause other sensations, such as numbness, pins and needles and tingling. As a result pain can sometimes be unpredictable.
Types of pain
One type of pain is acute pain; this is a short lived (up to 30 days) but intense pain (also known as acute pain). This tends to indicate some form of injury, hence when the injury heals the pain ceases too. Another type of pain is Chronic pain, which lasts longer than acute pain (duration of more than six months) but can be mild or intense.
How do we classify pain?
Nociceptive pain– in this case there is a stimulation of peripheral nerve fibres. Receptors here detect temperature (heat/cold), mechanical activities (crushing/tearing) and chemical activities (chilli powder in eyes).
Deep somatic Pain – This is a type of nociceptive pain. Somatic pain (muscular-skeletal pain) is the name given to pain which can be felt on the skin, muscle, joints, bones and ligaments. This type of pain tends to be aching, poorly localized pain. An example would be sprained ankles.
Superficial pain- this is initiated by activation of nociceptors in the skin or other superficial tissue. These receptors are capable of sensing inflammation, stretch and ischemia. It tends to be located in internal organs and main body cavities, such as thorax (lungs and heart), abdomen (bowels, spleen, liver and kidneys), and the pelvis (ovaries, bladder, and the womb.)
Neuropathic Pain- This is a type of non-nociceptive pain. The pain can originate from the peripheral nervous system or the central nervous system. It may be caused by nerve degeneration in cases such as stroke and multiple-sclerosis or it may have been caused due to a trapped nerve (there is pressure on the nerve). A slipped disc will cause nerve inflammation, which will trigger neuropathic pain as will a nerve infection, for example shingles.
Sympathetic Pain- this type of pain tends to occurs after a fracture. This pain is non-nociceptive hence there are no specific pain receptors. As with neuropathic pain, the nerve is injured, becomes unstable and so the brain receives abnormal, which it interprets as pain.
Phantom Pain- this involves the sensation of pain in a part of the body that has been removed. Though no one knows for sure why amputees have phantom pain there are possible explanations which are widely accepted.
- Memory of limb pain – some researchers theorise that brain had become accustomed to the pain when the limb was badly damaged. So even when the limb has been removed, the brain continues to sense the same kind of pain
- Nerve bundle stimulation – Others suggests that nerves around the amputation are stimulated in some way, sending signals to the brain which it interprets these as pain.
- Rewiring of the nervous system – there has also been evidence to show that that when a limb is amputated, changes take place in the brain and spinal cord which may mean that pain is interpreted differently however it is not clear if this causes phantom pains.