Pain is often classified as:
Pain can also be classified according to its cause.
The type of
analgesics are used to treat pain may differ, depending on whether or not a patient's
primary pain problem is due to nociceptive pain, neuropathic pain, or a combination
of both types of pain.
Transduction
Transmission
Perception
The first phase, transduction, begins when a painful or noxious stimulus causes tissue damage. The damaged cells release substances that lead to the generation of an action potential. Prostaglandins, bradykinin, serotonin, substance P, and histamine are some of the substances released in response to tissue damage.
In the next phase, transmission, the action potential continues from the site of damage to the spinal cord, where it ascends up the spinal cord to higher centers in the brain.
The third phase, perception, is the conscious awareness of pain.
The fourth phase is modulation or inhibition of painful or nociceptive stimuli. In the modulation phase, neurons descending from the brain release substances that inhibit the transmission of painful impulses. Analgesic drugs work at different steps of these processes to relieve pain.