What is pain?
Pain - jabbing, throbbing, burning, stinging, tingling, nagging or aching, over with in seconds, minutes or hours, or lasting for days, months or years . We have all experienced different types of pain at different times and for different reasons. On this site, you can learn about different aspects of pain in more detail, including the science behind pain, and how to control it.
Pain means different things to different people, and different things to the same person at different times.
Pain is something that you feel physically – your body senses it. We know a great deal about the physical aspects of pain.
To learn more about the nerves and other body structures involved in pain, click here.
Pain is also something you feel emotionally. Pain is subjective, affected by your current and past experiences, and your individual bodily response to pain. It is also affected by psychological factors from day to day. For example, on days that you are feeling down, you may notice pain more than on days when you are feeling happy. So it can sometimes be hard for doctors to understand exactly what you are feeling with your pain.
What is referred pain?
Referred pain is a term used to describe a situation in which you feel pain at a site in your body that is distant from the cause of the pain. For example, someone with liver or gall bladder problems may feel pain in their shoulder, and someone with pancreatic cancer may feel the pain in their back (these are not common causes of back and shoulder pain).
The messages about the tissue damage from one region (Region A) enter the spinal cord at the same level as the spinal nerves from another region (Region B), and the brain interprets the message as coming from Region B rather than the area where the tissue is damaged (Region A). This usually happens when the damaged tissue is in an area that has a small number of sensory neurones (e.g. an internal organ such as the gut) and joins nerves from an area that has a lot of sensory neurones (such as the skin).
What is the gate control theory?
When pain messages reach your spinal cord, they have to pass specialised nerve cells, which filter the pain messages on their way to your brain. They act as a gate: if the gate is open, the pain messages will pass through and if it’s closed, they won’t. The gate cells are affected by inputs from several different sources.
Firstly, the gate is affected by messages from nerve fibres that transmit touch (A-beta fibres). If there are more touch signals from the rubbing than there are pain signals from the injury, they can close the gate and decrease the transmission of pain signals. This explains why rubbing a sore area makes it feel better and is also how some pain therapies work, such as massage, transcutaneous nerve stimulation (TENS) and acupuncture.
Secondly, your brain can send messages to the gate that influence your perception of pain. It may signal nerve cells to release natural painkillers, such as endorphins. These can block the pain messages from getting in at the gate. The production of these natural painkillers can be increased or decreased by psychological and emotional processes, such as your present thoughts, your past experiences and even meditation. Stress, excitement and vigorous exercise can also affect your production of endorphins, which is why you sometimes do not notice pain straight away after a stressful situation or a sports competition, and then get a “let-down” reaction some time after. It is also why gentle exercise can help you to control chronic pain.
Terminology
- Endorphins : Naturally occurring molecules made up of amino acids, the building blocks of proteins. Endorphins attach to special receptors in the brain and spinal cord to stop pain messages. These are the same receptors that respond to morphine and other opioid analgesics.
- Enkephalins : Naturally occurring molecules in the brain. Enkephalins attach to special receptors in your brain and spinal cord to stop pain messages. These are the same receptors that respond to morphine and other opioid analgesics. Enkephalins also affect other functions within the brain and nervous system.