{"id":"2281","type":{"id":"7","name":"Physiologic Processes","urlId":"physiological-process","subtypes":[],"schema":"http:\/\/schema.org\/Article","numTerms":0},"subtype":{"id":"151","name":"Neurophysiology","urlId":"neurophysiology"},"urlId":"pain-pathways","role":"term","course":{"id":"1","urlId":"neuroanatomy","name":"Neuroanatomy"},"children":[],"name":"Pain Pathways","demo":0,"description":"\u003E ### **Spinothalamic Tract**\n\n### **Dorsal Root \u0026 Spinal Cord**\n* The dorsal horn receives sensory innervation.\n* The dorsal root receives sensory fibers.\n- The dorsal root ganglion houses the primary sensory neuron.\n- It is pseudounipolar, meaning it sends fibers both towards the spinal cord and also toward the periphery.\n* Indicate that where the roots merge, they form the mixed spinal nerve.\n* The sensory nerve activates a neuron in the dorsal horn (nociception most notably involves neurons of lamina I).\n* Spinothalamic tract (STT) fibers cross within the spinal cord to the contralateral side. \n\n### **Spinothalamic Projection**\n* Leg fibers synapse within the lumbar spinal cord and then decussate and ascend the anterolateral cord and brainstem to the thalamus.\n* Arm fibers synapse within the cervical spinal cord, and, also decussate and ascend the anterolateral cord and brainstem to the thalamus.\t\n* Trigeminothalamic fibers decussate within the pons and ascend the brainstem, medially, to the thalamus.\n\n### **Thalamocortical Projection**\n* Leg fibers project to the midline region; they terminate in the posterior paracentral gyrus.\n* Arm fibers project from the lateral thalamus to the upper convexity of the postcentral gyrus, lateral to the leg fibers.\n* Facial fibers project from the medial thalamus to the lateral cerebral hemisphere.\n\n# Medial-lateral orientation\n* Note that medial-lateral orientation of these fibers in the cerebral cortex is opposite of that in the thalamus.\n\n### **Additional Pain Projection Fibers**\n* Pathways, such as the spinoreticular, spinomesencephalic, and spinohypothalamic tracts, and the cervicothalamic tracts all also carry noxious stimuli from their self-named origins and termination sites and synapse in many regions, including the nuclei we addressed with the descending pain modulatory system.  Pain is more than simply the detection of a direct noxious stimulus, it is the emotional integration of many different influencing stimuli.\n* For a detailed understanding of these pathways, as well as the trigeminothalamic tracts, and the correlating neurotransmitters that play a role in pain, review our tutorials on the: [Midbrain](https:\/\/drawittoknowit.com\/course\/fundamental-neuroscience\/regional-neuroscience\/brainstem\/1137\/the-midbrain?curriculum=fundamental-neuroscience), [Pons](https:\/\/drawittoknowit.com\/course\/fundamental-neuroscience\/regional-neuroscience\/brainstem\/271\/the-pons-new?curriculum=fundamental-neuroscience), \u0026 [Medulla](https:\/\/drawittoknowit.com\/course\/fundamental-neuroscience\/regional-neuroscience\/brainstem\/272\/the-medulla-new?curriculum=fundamental-neuroscience).\n\n### **descending pain modulatory system**\n## Origins\n* Originates from numerous regions, including the anterior cingulate gyrus, amygdala, insula, etc...  And along its descent innervates the:\n## Periaqueductal gray area\n* The periaqueductal gray area at the midbrain level.\n## Parabrachial complex\n* The parabrachial complex in the dorsal pons at the superior cerebellar peduncle, which comprises the \u0022brachium conjunctivum\u0022.\n## Rostral ventromedial medulla\n* The rostral ventromedial medulla.\n## Dorsal horn\n* The dorsal horn of the spinal cord where they inhibit pain pathways.\n\n### **Clinical Terminology**\n* As a final part of this tutorial, let\u0027s learn some key clinical terminology, so we can get a sense of all of the ways that pain can manifest.\n## Pain types:\n* Neuropathic pain is a broad term, which can refer to pain that stems from any somatosensory nervous system lesion or pathologic process.\n* Whereas neuralgia is a more specific term, which refers to pain in a nerve distribution (or in the distribution of multiple nerves).\n* And neuritis specifically refers to inflammatory nerve pain.\n## Abnormal pain responses:\n* Hyper\/hypo-esthesia refers to an increased (hyper) or decreased (hypo) sensitivity to a any sensory stimulus \u2013 it\u0027s a broad term.\n* Whereas hyper\/hypo-algesia specifically refers to an increased (hyper) or decreased (hypo) pain response to a noxious stimulus.\n## Unexpected pain: \n* Allodynia refers to pain to a non-noxious stimulus, such as the bed-sheets brushing over your feet.  This is especially common in complex regional pain syndrome (aka reflex sympathetic dystrophy).\n## Abnormal sensations:\n* Dysesthesia, which refers to an unpleasant response and can encompass allodynia or hyperalgesia.\n* Whereas, paresthesia is a similar term that describes an abnormal sensation but the sensation isn\u0027t unpleasant.\n## Absence of pain:\n* Analgesia refers to the absence of pain to a painful stimulus.","keywords":[],"images":[{"id":"5472","url":"term\/images\/somatosensory-pain-pathways-5472.png","title":"somatosensory Pain Pathways","demo":false}],"radiographs":[],"curricula":[{"id":"1","level":"graduate","category":"individual","urlId":"neuroanatomy","name":"Neuroanatomy","subjectGroups":[{"id":"4","name":"Autonomics \u0026 Pain","urlId":"autonomics","subjects":[{"id":"6376","urlId":"pain","name":"Pain","tutorials":[{"id":"1680","urlId":"nociception-pain","title":"Nociception Pathways","hasQuizQuestions":0,"hasNotes":0,"hasStarterImage":0,"hasSlides":0}]}],"numTutorials":1}]},{"id":"3","level":"graduate","category":"individual","urlId":"physiology","name":"Physiology","subjectGroups":[{"id":"173","name":"Systems Neuroscience","urlId":"neurological-special-senses","subjects":[{"id":"735","urlId":"special-senses","name":"Special Senses","tutorials":[{"id":"1680","urlId":"nociception-pain","title":"Nociception Pathways","hasQuizQuestions":0,"hasNotes":0,"hasStarterImage":0,"hasSlides":0}]}],"numTutorials":1}]},{"id":"10","level":"undergraduate","category":"individual","urlId":"fundamental-neuroscience","name":"Neuroscience Fundamentals","subjectGroups":[{"id":"1700","name":"Sensory System","urlId":"sensory-system","subjects":[{"id":"498","urlId":"sensory-system","name":"Sensory System","tutorials":[{"id":"1680","urlId":"nociception-pain","title":"Nociception Pathways","hasQuizQuestions":0,"hasNotes":0,"hasStarterImage":0,"hasSlides":0}]}],"numTutorials":1}]},{"id":"24","level":"graduate","category":"individual","urlId":"neurological-system","name":"Neurological System","subjectGroups":[{"id":"402","name":"Autonomic Nervous System","urlId":"physiology","subjects":[{"id":"3146","urlId":"pain","name":"Pain","tutorials":[{"id":"1680","urlId":"nociception-pain","title":"Nociception Pathways","hasQuizQuestions":0,"hasNotes":0,"hasStarterImage":0,"hasSlides":0}]}],"numTutorials":1},{"id":"766","name":"Multiple Sclerosis \u0026 Pain","urlId":"movement-disorders-white-matter-diseases","subjects":[{"id":"3149","urlId":"anesthesia-pain","name":"Anesthesia \u0026 Pain","tutorials":[{"id":"1680","urlId":"nociception-pain","title":"Nociception Pathways","hasQuizQuestions":0,"hasNotes":0,"hasStarterImage":0,"hasSlides":0}]}],"numTutorials":1}]},{"id":"25","level":"postgraduate","category":"neurology","urlId":"neurosciences-abpn-moc","name":"Neurology - 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