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==Physiology and Pathophysiology of Pain Transmission==

==Physiology and Pathophysiology of Pain Transmission==

Two types of nocieptive fibres (neurons) exist. C-fibres are slow-conducting and unmyelinated, whereas A-delta-fibres are small, fast-conducting, myelinated structures. The cell bodies of these neurons are located in the dorsal root ganglion, and the neurons are bipolar. The sensory nerve endings conduct afferent impulses to the cell body, and fibres then extend to the dorsal horn of the spinal cord. Here, ascending information is transmited to the cortext via several "relay stations", including the [[Macroscopic Anatomy of the CNS#The Forebrain|thalamus]], the reticular formation, the [[Macroscopic Anatomy of the CNS#Pons|pons]] and the amygdala. These modulate the signal on its journey towards conscious perception. Local [[Macroscopic Anatomy of the CNS#Reflex Arcs|reflex arcs]] may also be stimulated in the dorsal horn, producing spinal reflexes such as the withdrawal reflex.  

Two types of nocieptive fibres (neurons) exist. C-fibres are slow-conducting and unmyelinated, whereas A-delta-fibres are small, fast-conducting, myelinated structures. The cell bodies of these neurons are located in the dorsal root ganglion, and the neurons are bipolar. The sensory nerve endings conduct afferent impulses to the cell body, and fibres then extend to the dorsal horn of the spinal cord. Here, ascending information is transmited to the cortext via several "relay stations", including the [[Forebrain - Anatomy & Physiology|thalamus]], the reticular formation, the [[Hindbrain - Anatomy & Physiology#Pons|pons]] and the amygdala. These modulate the signal on its journey towards conscious perception. Local [[Reflex Arcs - Anatomy & Physiology|reflex arcs]] may also be stimulated in the dorsal horn, producing spinal reflexes such as the withdrawal reflex.  

There is a large amount of plasticity in the pain transmission system: modulation of nociceptive transmissions occurs at every level, from the periphery to the cortex. This modulation may be ascending or descending, short-term or [[#Chronic pain|persistent]]. It has the ability to change the pain sensation from a protective, physiological response into a more pathological one, where pain is perceived in the abscence of tissue damage or may persist once the noxious stimulus has subsided.  

There is a large amount of plasticity in the pain transmission system: modulation of nociceptive transmissions occurs at every level, from the periphery to the cortex. This modulation may be ascending or descending, short-term or [[#Chronic pain|persistent]]. It has the ability to change the pain sensation from a protective, physiological response into a more pathological one, where pain is perceived in the abscence of tissue damage or may persist once the noxious stimulus has subsided.