1. Nociceptors special receptors that respond only to noxious stimuli and generate nerve impulses which the brain interprets as"pain omote Mast cell Substance P Histamine Dorsal root ganglion Blood Noxious Substance P
1. Nociceptors • special receptors that respond only to noxious stimuli and generate nerve impulses which the brain interprets as "pain
Nociopectors Tissue damage increases K, prostaglandin, serotonin, and bradykinin levels, thus activating the nociceptor Substance P released from Adequate Stimulation nerve endings, increase capillary permeability, and 0 contributes to inflammation Temperature 0 Blood vessel -Mechanical damage Substance P 0 Chemicals (released from Bradykinin damaged tissue SErotonin Bradykinin, serotonin, histamine, K+ Lesion acids, acetylcholine, proteolytic enzymes can excite the chemical Nociceptive Prostaglandin axon type ot pain Histamine 0 Substance P Prostaglandins and substance p enhance the sensitivity of pain endings but do not directly excite them Mast cell Substance P causes mast cells to release histamine which in turn activates nociceptor endings
Adequate Stimulation –Temperature –Mechanical damage –Chemicals (released from damaged tissue) Bradykinin, serotonin, histamine, K+ , acids, acetylcholine, proteolytic enzymes can excite the chemical type of pain. Prostaglandins and substance P enhance the sensitivity of pain endings but do not directly excite them. Nociopectors
Hyperalgesia The skin, joints, or muscles that have already been damaged are unusually sensitive a light touch to a damaged area may elicit excruciating pain Primary hyperalgesia occurs within the area of damaged tissue Secondary hyperalgesia occurs within the tissues surrounding a damaged area
Hyperalgesia The skin, joints, or muscles that have already been damaged are unusually sensitive. A light touch to a damaged area may elicit excruciating pain Primary hyperalgesia occurs within the area of damaged tissue Secondary hyperalgesia occurs within the tissues surrounding a damaged area
2. Localization of pain Superficial somatic pain arises from skin areas Deep somatic pain arises from muscle, joints, tendons(肌间)& fascia(筋膜) Visceral Pain arises from receptors in visceral organs
2. Localization of Pain • Superficial somatic pain arises from skin areas • Deep somatic pain arises from muscle, joints, tendons （肌间） & fascia (筋膜） • Visceral Pain arises from receptors in visceral organs
3. Fast and slow pain Most pain sensation is a combination of the two types of message sharp pain conducted by the a fibres dull pain conveyed along C fibres
• Most pain sensation is a combination of the two types of message. – sharp pain conducted by the A fibres – dull pain conveyed along C fibres 3. Fast and Slow Pain