THE PERCEPTION OF PAIN

Pain is a complex and multifaceted experience that involves both objective physiological processes and subjective perceptions. Here's a breakdown of the sensation of pain.

The Perception of Pain

In order to look closely at how each person perceives pain, let's consider both objective and subjective aspects of pain.

OBJECTIVE SENSATION OF PAIN

Nociception: The objective aspect of pain begins with nociception, which is the detection of harmful stimuli by specialised nerve endings called nociceptors. Nociceptors are relatively unspecialised nerve endings that are located throughout the body in the skin, muscles, several organs and other tissues. They tend to initiate the sensation of pain, after they’ve been activated by different stimuli such as heat, pressure, chemicals or tissue damage. Perhaps something rather curious is that our central nervous system does not have nociceptors and, therefore, cannot perceive pain. The pain that we experience within the brain usually comes from nerve endings in the blood vessels (next time you have a headache, you’ll be aware that it’s not the brain that’s hurting, but perhaps some of the arteries and veins within it).

Transmission of Pain Signals: When pain receptors are activated, they send electrical signals in the form of nerve impulses to the spinal cord and then to the brain. The bodies of the cells whose branches act as pain receptors, are based in the dorsal root ganglia in the spine. Equally, the receptors that we have on our faces have their cell bodies in the trigeminal ganglion. This is the reason why some injuries that affect the spine can leave us without the sensation of pain (or perhaps other feelings): because the connection between the receptor and the body of the cell has been cut. Pain signals travel along specific pathways in the nervous system, relaying information about the type, intensity and location of the pain stimulus to the brain.

Processing in the Central Nervous System (CNS): Once the pain signals reach the brain, they are processed and interpreted in different regions, including the somatosensory cortex, the limbic system (responsible for emotions) and the frontal cortex (responsible for decision-making). The brain integrates the information it receives from various routes and creates a perception of pain and generates appropriate responses. It also learns from it, for future reference.


SUBJECTIVE SENSATION OF PAIN

Perception: Pain perception is not just an objective nerve impulse that goes through various nerves, all the way to the brain. It is also something subjective: pain varies from person to person. It is influenced by various factors such as genetics, past experiences, cultural background, emotional state and individual pain thresholds. The perception of pain refers to how an individual interprets and experiences the pain signals received from the nervous system.

Emotional and Psychological Factors: Emotional and psychological factors significantly impact the subjective experience of pain. For example, stress, anxiety, depression and fear can amplify the perception of pain, making it feel more intense than the actual physical stimulus. Conversely, positive emotions, distraction and relaxation techniques can modulate pain perception and provide relief.

Pain Expression: Pain often leads to observable behavioural and physiological responses, such as facial expressions, body language and even changes in heart rate and blood pressure. These expressions are outward manifestations of the subjective pain experience and are used by healthcare professionals to assess and evaluate pain levels.