Physiology of Pain

Posted by e-Medical PPT
“Pain can be an adaptive sensation, an early warning to protect the body from tissue injury.  By the introduction of hypersensitivity to normally innocuous stimuli, pain may also aid in repair after tissue damage.
Pain can also be maladaptive, reflecting pathological function of the nervous system.”
There are multiple molecular and cellular mechanisms that operate in sensory pathways to generate neural signals that we interpret as pain.

Nociceptors
Nociceptive pain serves as a warning device which is activated in response to impending damage to an organism.Nociceptive pain is activated only by noxious stimuli acting on a specialized high-threshold sensory apparatus.Pain receptors or nociceptors are free sensory nerve endings that respond to a variety of noxious stimuli (chemical, mechanical, or thermal) that cause or have the potential to cause tissue damage
Sensory input initiates adaptive, protective responses, such as a reflexive action.
Nociceptor Ad and C somatosensory afferent terminals transduce external noxious stimuli into action potentials that are conducted to the dorsal horn of the spinal cord.
Fast impulses for acute sharp pain travel in the neospinothalamic tract.
Slower impulses for chronic or dull pain travel in the paleospinothalamic tract.
These two tracts connect with the reticular formation in the brainstem, hypothalamus, and thalamus as they ascent to the somatic sensory cortex and pre-frontal association areas.

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