Pain.docx

Pain - \"an **unpleasant sensory and emotional experience** associated with actual or potential tissue damage \" - *International Association for the Study of Pain* - Sensation and nociception --- three-neuron sequence - Receptor or free nerve ending 🡪 1^st^ order neuron (A-b...

Pain - \"an **unpleasant sensory and emotional experience** associated with actual or potential tissue damage \" - *International Association for the Study of Pain* - Sensation and nociception --- three-neuron sequence - Receptor or free nerve ending 🡪 1^st^ order neuron (A-b, A-d, C fibers) 🡪 dorsal horn 🡪 - Descending Pathways - Activity (excitatory or inhibitory) after the cortex receives input - Pain managed by targeting descending pathways **Pain Control Theories** - Peripheral Pain Modulation - Desensitize peripheral nociceptors - Slow conduction velocity - Usually with cryotherapy - Spinal Level Pain Modulation - ***Gate control theory*** - Explains how a stimulus that activates only non-nociceptive nerves can inhibit pain - Proposes a gating mechanism in the dorsal horn of the spinal cord - A-b, A-d, and C fibers all synapse with 2^nd^ order neurons in dorsal horn - Impulses traveling along A-b can also interact with substantia gelatinosa (SG) - SG has inhibitory interneurons inhibit transmission between first and second order nociceptive neurons - Enkephalin interneurons: release enkephalin (natural opioid) - A-b impulses stimulate (+) SG (enkephalin interneuron)🡪 enkephalin release 🡪 inhibition of A-d and C fiber transmission to 2^nd^ order neuron - Good example is when rubbing your head after bumping it - - Pain modulation involves both ascending and descending neural components - Any that occurs above the level of the spinal cord is termed *supraspinal* - Anything that travels from brain to spinal cord or brainstem is termed *descending* - Noxious pain modulation - Elicitation of C-fibers in affected region stimulates areas in brain/brainstem which activates descending inhibitory neurons - Raphe nucleus 🡪 Serotonin containing neurons - Pituitary gland/hypothalamus 🡪 norepinephrine containing neurons  *Question: how does icing immediately after an injury help with pain?* - Pain after acute injury - Force could have injured nerve endings - Hypoxia and chemical changes around nerve endings cause chemical nociception - Chemical irritation of healthy nerve endings reduces mechanical nociceptive threshold - **Not always due to nociception** - **https://www.youtube.com/watch?v=gwd-wLdIHjs**