Summary
Nociceptors send signals through the spinal cord, modulated by the gate control and endogenous opioids.
In depth
Aδ fibres (fast, sharp) and C fibres (slow, dull) carry nociceptive signals to the dorsal horn, then to the thalamus and cortex. The gate control theory says non-painful input can inhibit pain transmission, why rubbing a bump helps. Descending pathways use endorphins and serotonin.
Pain has sensory and affective components. Central sensitisation increases responsiveness. Placebo analgesia involves endogenous opioids.
Key idea: pain is produced by the brain and modulated at many levels.
Nociceptors are free nerve endings with TRP channels (TRPV1 detects heat above 43 degrees and capsaicin, TRPA1 detects irritants such as mustard oil). Signals travel via Adelta (first, sharp pain) and C fibres (second, dull burning pain) to the dorsal horn of the spinal cord, cross, and ascend in the spinothalamic tract to the thalamus and then to the somatosensory cortex (location and intensity) and anterior cingulate and insula (unpleasantness). Melzack and Wall's gate control theory (1965) says that non-painful input (rubbing) can inhibit pain transmission in the dorsal horn.
Descending pathways from the periaqueductal grey and raphe release endorphins and serotonin that inhibit pain; placebo and stress-induced analgesia use them. Chronic pain involves central sensitisation and glia, and neuropathic pain arises from nerve injury. Treatments: NSAIDs, opioids, gabapentinoids, nerve blocks, TENS, and psychological methods. Congenital insensitivity to pain from Nav1.7 mutations shows the danger of lacking pain.
Remember: pain is an output of the brain protecting the body, and not just a signal from tissue.
Frequently asked questions
What is Pain Pathways?
Nociceptors send signals through the spinal cord, modulated by the gate control and endogenous opioids.
Which area of biology covers Pain Pathways, and how advanced is it?
Pain Pathways is one of the 54 topics in Neuroscience. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Basal Ganglia, Brain-Machine Interfaces, Spinal Cord Functions.
Can you give an example of Pain Pathways?
Phantom limb pain arises after amputation.
What should I learn before Pain Pathways?
Work through the Beginner topics in Neuroscience first, such as Nervous System, Neuron, Central and Peripheral Nervous Systems, then return to Pain Pathways. Advanced topics assume the Intermediate vocabulary.
What topics are related to Pain Pathways?
The closest topics to Pain Pathways are Basal Ganglia, Brain-Machine Interfaces, Spinal Cord Functions, Cerebellum and Motor Learning. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Pain Pathways?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Pain Pathways. To practise the whole of Neuroscience, use the Neuroscience quiz.
How is Pain Pathways different from Basal Ganglia?
Pain Pathways: Nociceptors send signals through the spinal cord, modulated by the gate control and endogenous opioids. Basal Ganglia: Deep nuclei that select and initiate actions, disrupted in Parkinson's and Huntington's diseases. Read both side by side and note what each one explains.
How should I study Pain Pathways step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Basal Ganglia and explain the difference aloud. Finally, take the Neuroscience quiz and come back to this page for any question you miss.