People feel pain when exposed to a damaging stimulus, allowing the individual to respond so that this pain goes away. Often, it acts as an alarm telling us that there is something wrong with the body, and therefore we go to hospitals and get treated, as it usually underlies a problem. Pain is subjective and differs with various people and problems. For some, they may feel a sharp stab, whereas for others it could be merely be a pinch.
So how do we feel pain?
When we touch something sharp or a surface that is very hot, specific pain receptors called nociceptors are activated. These sensory neurons react by sending signals to the spinal cord and brain, alerting us of the dangers and protecting body tissues from damage. Nociceptors will respond to typically three types of stimulus:
- Temperature (e.g. hot or cold surfaces)
- Mechanical (stretch/ strain e.g. pulling a muscle)
- Chemical (e.g. change in pH due to a local inflammatory process)
As well as there being different types of stimulus for nociceptors, nociceptors are categorised into two groups depending on how fast they transmit these pain signals, with the first one being A fibre axon. These are nerve fibres insulated by a fatty sheath called myelin, which allows the rapid transmission of signals. However, C fibre axons transfer these signals to the brain more slowly as a result of not being surrounded by the myelin sheath present in the A fibre axons. A person will therefore experience pain within two stages – signals from the A fibres will reach the spinal cord and brain first, and the person will feel sharp, stinging pain, shortly followed by C fibres which will still produce a persistent pain after the stimulus has been removed until it is healed.
Types of pain
- Acute pain- This sort of pain is short term and will typically last between 3 to 6 months. The main cause for this would be tissue injury and will usually be sharp and severe at the start, before gradually improving as the injuries heals. Other causes may include surgery, burns or cuts and dental work.
- Chronic pain – This is more of a long-term pain, which exists even after the original injury has healed and is ongoing for over six months e.g. low back pain. This is because the signals responsible for producing pain are still active within the nervous system. This may result in those with the pain to suffer from other effects, including very little energy and possibly even depression and anger.
As annoying as it is, we would not know if there was something wrong with our body without pain. So, this leads to the question; what about those who cannot feel pain at all?
Congenital insensitivity to pain with anhidrosis is a rare, untreatable disease where the person will not be able to feel any pain, as well as not being able to sweat. It is usually identified at birth as infants are unable to regulate their body temperature, due to the inability to sweat, which can then lead to hyperthermia or high fevers as they cannot cool down.
Being unable to feel pain can lead to a lot of problems. They may suffer from very large injuries without even noticing and as a result, this can be dangerous since the individual may never realise and lead to wounds turning into infections. Imagine if you were to break your leg and required immediate medical care but could not feel any pain at all. Common problems for children with CIPA include biting their finger and drawing blood, and suffering from eye injuries as they start rubbing it too hard.
While people with CIPA cannot perceive pain or temperature, they are still able to touch and feel pressure. It is a result of a genetic mutation of a gene called NTRK1 (a receptor) which then results in a protein that cannot transmit pain and temperature signals. Additionally, the nerves also responsible for sending signals to the sweat glands are missing, which is why they cannot sweat.
Pain acts as an important sense of our body that is there for a reason. It allows us to become aware if something is wrong within our body and needs to be fixed. Without it, there is clear evidence about what problems will occur and how our body will suffer from the consequences.
- Physiopedia, “Nociception” [online] <https://www.physio-pedia.com/Nociception>
- Verywell Health(2020) ,”What are Nociceptors?” [online] Last accessed date : 08/04/2020 <https://www.verywellhealth.com/what-are-nociceptors-2564616>
- Katie Lambert,” How CIPA Works” [online] <https://science.howstuffworks.com/life/inside-the-mind/human-brain/cipa1.htm>
- Heidi Moawad (2020), “CIPA disease: When a person can’t feel pain” [online] Last accessed date: 16/04/2020 <https:www.verywellhealth.com/cipa-disease-when-a-person-can-t-feel-pain-4122549
- Healthline (2018),”Types of pain: How to recognise and talk about them” [online] Last accessed date: 29/11/2018 <https://www.healthline.com/health/types-of-pain#chronic-pain