From the Guidelines
Pain processing in the nervous system involves a complex sequence of events that translate harmful stimuli into the conscious experience of pain, with the most recent evidence suggesting that this process is influenced by biological, psychological, and social factors 1. The process of pain transmission begins with the detection of noxious stimuli by specialized nerve endings called nociceptors, which convert the stimuli into electrical signals that travel along peripheral nerves (A-delta and C fibers) to the spinal cord.
- In the dorsal horn of the spinal cord, these signals synapse with second-order neurons that cross to the opposite side and ascend to the brain through pathways like the spinothalamic tract.
- The signals reach the thalamus, which acts as a relay station, and are then distributed to various brain regions including the somatosensory cortex (for pain location and intensity), the limbic system (for emotional aspects of pain), and the prefrontal cortex (for cognitive processing). Throughout this pathway, the nervous system can modulate pain signals through descending pathways that release neurotransmitters like endorphins, serotonin, and norepinephrine, which can inhibit pain transmission, as supported by the study published in the British Journal of Pharmacology 1. This modulation explains why factors such as stress, attention, and expectations can influence pain perception, and is in line with the definition of pain provided by the International Association for the Study of Pain (IASP) as “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage” 1. The nervous system's ability to process pain is a complex and multifaceted process that involves the integration of sensory, emotional, and cognitive information, and is influenced by a variety of factors, including biological, psychological, and social factors, as highlighted in the study published in 2022 1.
From the Research
Nervous System Processing of Pain
The nervous system processes pain through a complex interplay of messages sent from the periphery to the central nervous system and vice versa.
- Specific pathways play a vital role in carrying these messages, and modulating, or exacerbating their downstream effects 2.
- The anatomy and physiology of pain pathways from peripheral nociceptors to central nervous system areas involved in the perception and modulation of pain are crucial in understanding how the nervous system processes pain 3.
Pain Pathways and Targets
Pain involves various pathways and targets, including:
- Ion channels, receptors, and neurotransmitters that mediate different types of pain, such as neuropathic and inflammatory persistent pain 3.
- Peripheral nociceptors that detect and transmit pain signals to the central nervous system 2, 3.
- Central nervous system areas, such as the brain and spinal cord, that process and modulate pain signals 2, 3.
Pharmacological Treatments of Pain
Pharmacological treatments of pain, including neuropathic pain, involve various drugs and therapies, such as:
- First-line treatments, including tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, pregabalin, and gabapentin 4, 5.
- Second-line treatments, including lidocaine plasters, capsaicin high concentration patches, and tramadol 5.
- Third-line treatments, including strong opioids and botulinum toxin A 5.
- Alternative treatments, such as ibuprofen/acetaminophen fixed-dose combinations, which can be used as an alternative to opioids in managing common pain types 6.