II. Definitions
- Allodynia
- Nonpainful stimulus results in Perception of pain
- Hyperpathia
- Pain out of proportion to pain stimulus
III. See Also
IV. Anatomy
- Images
- Nociceptors
- Nociceptors, often Free Nerve Endings with specialized channels, detect painful, noxious stimuli
- Thermal pain (>43 C) triggers TRPV1 channels
- Mechanical pain (e.g. pressure, deformation, skin breakage) are detected by polymodal receptors
- Chemical pain (e.g. Capsaicin and other skin irritants, spices, toxins, acids) triggers TRP channels
-
Peripheral Nerves
- Pain signals follow two axonal paths
- A-delta axons (myelinated, faster at 20 m/s, carry immediate severe sharp Sensation)
- C axons (unmyelinated, polymodal, slow at 2 m/s, carry delayed dull, less intense pain)
- Skin Sensation follows Dermatomes
- Carry afferent pain signals back to the spinal cord posterior root (at the posterior horn of the grey matter)
Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
- Pain signals follow two axonal paths
-
Spinothalamic Tract (ascending sensory tract, anterior cord)
- Transmits pain and TemperatureSensation (as well as some light Touch Sensation)
- Fibers cross the midline within 1-2 spinal levels of their peripheral Sensory Nerve origin
- Courses to contralateral Thalamus and cerebral cortex (or terminates in Brain Stem)
- Descending Inhibitory Tract
- Hypothalamus releases hormonal signals
- Periaqueductal grey matter and periventricular nucleus (PVN) is chemically triggered by Hypothalamus
- Nucleus raphe magnus (NRM) is triggered by Neuronal signals from PVN
- Interneurons are triggered by NRM serotinergic Neurons
- Interneurons enter the Substantia gelatinosa (SG) in the dorsal horn of the spinal column
V. Pathophysiology: General
- Pain Perception Factors
- Response to Chronic Pain may be learned
- Reaction to pain may be reinforced (patient, family)
- Behavior may persist after pain resolves
- Modulation of Sensation
- First dorsal horn Synapse enhances or inhibits pain
- Modulation occurs in various locations
- Spinothalamic Tract
- Frontal cortex
- Descending inhibitory neuro-systems
- Pain Mechanisms
- Neuropathic pain
- Characteristics: Burning, stabbing or shooting pain
- Examples: Stroke, Radiculopathy
- Musculoskeletal pain or Mechanical compression pain
- Characteristics: Aching, soreness, stiffness
- Examples: Myofascial Pain Syndrome, Fibromyalgia, Low Back Pain
- Inflammatory pain
- Characteristics: Aching, swelling, hot, red
- Examples: Rheumatoid Arthritis, Postoperative pain, Septic Joint
- Neuropathic pain
- Dorsal horn Synapse physiology
VI. Pathophysiology: Gate Control Theory
- Specific pain fibers from injured tissues via
- Alpha fibers myelinated
- Delta and C-fibers unmyelinated
- Modulated at spinal cord gate
- Substantia gelatinosa
- Control transmission cells
- Spinothalamic Tract cephalad
- Descending signals (regulate gate at spinal cord)
- Pain transmission can be blocked by emotion or mood
- Sensory discriminative system
- Determines differences in sensory threshold
- Motivational Affective System
- Reciprocal relationship between mood and pain
- Central control processes
- Include unknown processes of pain
VII. Pathophysiology: Central Sensitization
- Central Sensitization is an inappropriate response to low level stimuli
- Exaggerated stimulus response, with lower thresholds triggering a pain response
- Pain persists after trigger is removed
- Ascending pain signals are amplified and pain inhibitory signals are suppressed
- Increased Cytokine concentrations after infections
- Sympathetic Nervous System hyperactivity
- Endogenous Opioid system changes
- Altered brain neuroplasticity
VIII. Resources
- Nociceptor (Wikipedia)
- Purves (2001) Neuroscience, 2nd edition. Sunderland, Nociceptors
Images: Related links to external sites (from Bing)
Related Studies
| Definition (MSH) | An increased sensation of pain or discomfort produced by mimimally noxious stimuli due to damage to soft tissue containing NOCICEPTORS or injury to a peripheral nerve. |
| Definition (CSP) | excessive sensitivity to painful stimuli. |
| Concepts | Sign or Symptom (T184) |
| MSH | D006930 |
| SnomedCT | 279078006, 140908006, 163706006, 55406008 |
| English | Hyperalgesias, HYPERALGESIA, Increase sensitiv to pain stim, hyperalgia, Hyperalgesic Sensations, Hyperalgesia [Disease/Finding], Hyperalgesia, hyperalgesia, Hyperpathia (finding), Hyperpathia, Hyperalgia, Increased sensitivity to painful stimulus, Hyperalgesia (finding), hyperpathia |
| Portuguese | HIPERALGESIA, Hiperpatia, Hiperalgesia |
| Spanish | HIPERALGESIA, Hiperpatía, hiperpatía, hiperpatia, hiperalgesia (hallazgo), hiperalgesia, Hiperalgesia |
| Dutch | hyperpathie, hyperalgesie, Algesie, hyper-, Hyperalgesie |
| French | Hyperpathie, HYPERALGIES, Hyperalgie, Hyperalgésie |
| German | Hyperpathie, HYPERALGIE, Hyperalgesie |
| Italian | Iperpatia, Iperalgesia |
| Japanese | ヒペルパチー, ﾋﾍﾟﾙﾊﾟﾁｰ, ﾂｳｶｸｶﾋﾞﾝ, 痛覚過敏 |
| Swedish | Hyperalgesi |
| Czech | hyperalgezie, Hyperpatie, Hyperalgezie |
| Finnish | Hyperalgesia |
| Russian | GIPERALGEZIIA, ГИПЕРАЛГЕЗИЯ |
| Croatian | HIPERALGEZIJA |
| Polish | Hiperalgezja, Przeczulica na bodźce bólowe |
| Hungarian | Hyperalgesia, Hyperpathia |
| Norwegian | Hyperalgesi, Økt smertesans, Økt smertefølelse |
Ontology: Nociceptors (C0028246)
| Definition (MSH) | Peripheral AFFERENT NEURONS which are sensitive to injuries or pain, usually caused by extreme thermal exposures, mechanical forces, or other noxious stimuli. Their cell bodies reside in the DORSAL ROOT GANGLIA. Their peripheral terminals (NERVE ENDINGS) innervate target tissues and transduce noxious stimuli via axons to the CENTRAL NERVOUS SYSTEM. |
| Definition (NCI) | A free nerve ending that is a receptor for painful stimuli. (Kanner) |
| Definition (CSP) | receptor for pain caused by damage to body tissue. |
| Concepts | Body Part, Organ, or Organ Component (T023) |
| MSH | D009619 |
| English | Nociceptors, Pain Receptors, Receptors, Pain, nociceptor, NOCICEPT, RECEPT PAIN, PAIN RECEPT, pain receptor, Nociceptive Neurons, Neuron, Nociceptive, Neurons, Nociceptive, Nociceptive Neuron, nociceptors, pain receptors, receptor pain, Nociceptor, Pain Receptor |
| French | Récepteurs à la douleur, Nocicepteur, Nocicepteurs, Récepteurs de la douleur |
| Swedish | Smärtreceptorer |
| Finnish | Kipureseptorit |
| Russian | BOLEVYE RETSEPTORY, NOTSIRETSEPTORY, NOTSITSEPTORY, NOTSITSEPTOR, БОЛЕВЫЕ РЕЦЕПТОРЫ, НОЦИРЕЦЕПТОРЫ, НОЦИЦЕПТОР, НОЦИЦЕПТОРЫ |
| Italian | Recettori del dolore, Neuroni nocicettivi, Nocicettori |
| Portuguese | Receptores de Dor, Neurônios Nociceptores, Nociceptores |
| Croatian | NOCICEPTORI |
| Polish | Receptory bólowe |
| Japanese | 侵害受容器, 痛み受容器, 有害受容体, 痛覚受容体, 痛覚受容器 |
| Czech | nociceptory, nociceptivní receptory, nociceptivní neurony, receptory bolesti |
| Norwegian | Nociseptorer, Smertereseptorer, Nocireseptorer |
| German | Nozizeptoren, Rezeptoren, Schmerz-, Schmerzrezeptoren |
| Dutch | Nociceptor, Nociceptoren, Pijnreceptoren, Receptoren, Pijn |
| Spanish | Nociceptores, Receptores del Dolor |
Ontology: Nociception (C0234194)
| Definition (MSH) | Sensing of noxious mechanical, thermal or chemical stimuli by NOCICEPTORS. It is the sensory component of visceral and tissue pain (NOCICEPTIVE PAIN). |
| Definition (NCI) | The stimulus-response process involving the stimulation of peripheral pain-carrying nerve fibers (e.g., C-fibers, A-delta fibers) and the transmission of impulses along peripheral nerves of the central nervous system, where the stimulus is perceived as pain. (Taber's) |
| Concepts | Organ or Tissue Function (T042) |
| MSH | D059225 |
| English | nociceptions, nociception, Nociceptions, Nociperceptions, Nociperception, Nociception |
| Russian | НОЦИЦЕПЦИЯ |
| Spanish | Nocicepción, Nocipercepción, Nociocepción |
| Polish | Nocycepcja |
Ontology: Allodynia (C0458247)
| Concepts | Finding (T033) |
| MSH | D006930 |
| SnomedCT | 247404004 |
| Japanese | 異痛症, ｲﾂｳｼｮｳ |
| English | Painfl response non-painf stim, Allodynia, allodynia, Painful response to non-painful stimulus, Allodynia (finding) |
| Czech | Alodynie |
| Hungarian | Allodynia |
| Norwegian | Allodyni |
| French | Allodynie |
| Italian | Allodinia |
| Spanish | alodinia (hallazgo), alodinia, respuesta dolorosa a estímulos no dolorosos, Alodinia |
| Portuguese | Alodínia |
| Dutch | allodynie |
| German | Allodynie |
