Information AboutPain Receptor |
| CATEGORIES ABOUT NOCICEPTOR | |
| sensory receptors | |
| nociception | |
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LOCATION Nociceptors are sensory Neuron s that are found in external Tissue s such as Skin , Cornea and Mucosa as well as in internal organs, such as the Muscle , Joint , Bladder and Gut . The cell bodies of these neurons are located in either the Dorsal Root Ganglia or the Trigeminal ganglia. TYPES AND FUNCTIONS There are several types of nociceptors and they are classified according to the stimulus modalities to which they respond: i.e. thermal, mechanical or chemical. Some nociceptors respond to more than one of these modalities and are consequently designated polymodal. Other nociceptors respond to none of these modalities (although they may respond to stimulation under conditions of inflammation) and have thereby earned the more poetic title of sleeping or silent nociceptors (Kandel et al, 2000). Thermal nociceptors are activated by noxious heat or cold, temperatures above 45°C and below 5°C (Kandel et al, 2000). Mechanical nociceptors respond to excess pressure or mechanical deformation. Polymodal nociceptors respond to damaging stimuli of a chemical, thermal, or mechanical nature (Kandel et al, 2000). Nociceptors may have either Aδ Fiber axons or more slowly conducting C Fiber axons. Thus, pain often comes in two phases, the first mediated by the fast-conducting Aδ fibers and the second part due to C fibers. Silent nociceptors do not usually fire Action Potential s, though they are much more likely to do so in the presence of Inflammation or damaging chemicals (Kandel et al, 2000). Together these nociceptors allow the organism to feel pain in response to damaging pressure, excessive heat, excessive cold and a range of chemicals, the majority of which are damaging to the tissue surrounding the nociceptor. PATHWAY Afferent nociceptive fibers (those that send information ''to'', rather than ''from'' the brain) travel back to the Spinal Cord where they form synapses in its Dorsal Horn . The Cells in the dorsal horn are divided into physiologically distinct layers called laminae. Different fiber types form Synapses in different layers. Aδ fibers form synapses in laminae I and V, C Fibers connect with neurons in lamina II, Aβ Fiber s connect with lamina IV. Information is then sent from the spinal cord to the Thalamus and the Cerebral Cortex in the brain. SEE ALSO
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