In July's version of 'pain tales' we looked into nerves and how they send messages to the brain (and back again). Nerves conduct messages from our muscles, skin and joints as electrical impulses to and from our brain. Even the brain itself is made up of trillions of nerves and connections, and then there are the nerves that supply to our vital organs.
So what can happen when all of this goes amiss? When nerves become hyper sensitive due to injury, pressure or in chronic pain?
We have all probably heard about brain plasticity. This ability for the brain to change, adapt, 'be plastic' in reaction to stimuli can also be demonstrated in the peripheral nervous system. This peripheral nervous system includes all nerves outside of the brain (or central nervous system).
Nerves are able to conduct electrical impulses or messages via their conductivity. Positive and negative ions pass over the nerve 'walls', charging them until the point that an impulse fires along the nerve. This is called an 'action potential'. Charged ions can rush into the nerve via sensors, also known as receptors or 'ion channels'. These are made of protein and 'listen out' or measure different stimuli. They are specific and specialised for just that stimulus. For example, light receptors in your eyes, or sound wave sensors in your ears.
There are only 3 types of sensors in your nerves for your muscle, skin and bones – one to detect the stimulus of temperature, one for mechanical changes (such as stretching, vibration, pulling) and one for chemical changes (such as adrenaline, acids, endorphins).
Changes detected by these 3 types of sensors will create the influx of ions to create a message that rushes along your nerve pathway to your brain, or back again. You may remember from previous discussions that these messages are NOT pain messages. Pain is the construct from the brain after weighing up all the information that the nerves have delivered for that time and that place.
The most amazing thing about these sensors is that their life is short- only living for a few days. They are always being replaced by new sensors and the type of sensor may change depending on what your brain decides is needed for your best survival. The brain does this by producing sensors proportionate to the stimuli around.
So, for example, if your posture is poor and you have rounded shoulders when you sit all day, the mechanical sensor numbers will be higher than the temperature or chemical ones in the nerves of this area of our body. This is because of the constant pulling loads on the nerves about your neck and upper back through your rounded shoulder and chin poked out. This makes for a very over sensitive area in your body, detecting lots of mechanical changes and forces and producing a higher rate of impulses from these nerves to the brain. Your brain may choose to ignore these, but will be more likely to feel more pain. And this makes for a tired painful neck and upper back. Sound familiar?
So back to 'plasticity' (and the good news if you suffer from pain)! The same can happen in reverse. The number of a particular sensor type in a nerve will reduce if the stimulus is less. And a return to a relatively balanced and stable number of each receptor type in all of your nerves. Using the same example of poor posture and rounded shoulders in our neck pain sufferers, better your posture –'mangoes under the chin', 'long tall neck', 'lifted breastbones' – move more, be stronger. This will decrease the mechanical pulling on your nerves up there, reduce the mechanical sensors about and therefore the number of impulses to your brain. The result – less pain!
So remember that nerve sensors are dying and being replaced every few days. Pain and sensitivity is always changing and that the pain you are in now is not fixed.