The brain is constantly receiving sensory information, not only from the tissues but also in the form of sight, hearing, smell and taste. It is also important to remember that thoughts, emotions and beliefs are nerve impulses too, which are processed by the brain and contribute to the output of neurotags. This is why certain smells remind you of things, or a piece of music is particularly poignant. Similarly, believing that your pain is due to tissue damage can create fear of re-injury, deconditioning and depression.
The sympathetic nervous system (SNS), the endocrine system and immune system are all very important players in bodily function, which includes chronic pain. All of these systems are activated by multiple sensory inputs such as sight, hearing, thoughts, beliefs, perception, mood and memory. Consider being spooked (stressed) while walking home one night in the dark. If you come across that situation again, chances are your SNS, endocrine system and immune system will all become activated in an attempt to protect you. Your SNS will release adrenalin from your adrenal gland, which increases your heart rate, improves vision and sends blood supplies to the muscles to enable you to fight or run. The adrenal glands also releases cortisol, which stimulates the liver to metabolise proteins and fats to provide energy for the stressful event and modulates your immune system activity. All of this is a great short-term protection mechanism for your body. But if they are constantly activated in the course of a faulty neurotag they start to become dysfunctional and lead to poor health and chronic pain.