Pain
Pathophysiology
There are different ways to classify pain:
Table 1. Source adapted from Carter, B. (2004)
Pathophysiological
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| Temporal |
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| Causative |
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Nocioceptive pain
Used to describe pain that is related to the degree of receptor stimulation by tissue injury (skin, muscle, joints and visceral tissues).
Consists of four processes(2):
1. Transduction: Depolarization at the peripheral nociceptors in response to stimuli.
2. Transmission: Stimuli proceed along afferent axons via myelinated A fibers and nonmyelinated C fibers to the spinal cord and then on to higher centers in the brain.
3. Perception: Impulses reach higher centers and the individual recognizes pain.
4. Modulation: Complex systems modulate and inhibit pain perception. This involves mediation by the binding of endogenous opioids compounds to receptors mu, delta and kappa. These endorphins are widely distributed and tied to systems regulating pain and stress. Also other neurotransmitters, such serotonin and norepinefrine, play a role in the endogenous pain modulating system through structures such as descending inhibiting pathways(2).
As described in Table 1, nociceptive pain can be classified as somatic and visceral:
Somatic pain:
- Refers to tissues derived from the embryological mesoderm and includes bone, muscle, ligaments, fascia, ect.
- It is characterized by being well localized and is the most common pain suffered by cancer patients.
- Usually it is described as aching, squeezing, stabbing or throbbing.
Visceral pain:
- Refers to those tissues and organs derived from the embryological endoderm and includes stomach, bowel, liver, pancreas, kidney, bladder, uterus, etc.
- It is not always associated with direct visceral injury and is most often felt on the surface of the body in a particular area and is called referred pain.
- It is described by patients as diffuse and poorly localized and dull, crampy or achy.
