Pain and Mobility
10.2 Pain and Mobility Concepts
Concepts Related to Pain
This resource provides a basic introduction to the concept of pain as it relates to pharmacology. The concept of pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage”[1].
The example concept map in figure 10.2a provides a summary of the key information necessary to understand pain informed by several resources.[2]
You are encouraged to revisit this map after you have completed the chapter.
Before addressing the medications that are used to treat analgesic and musculoskeletal conditions in our clients, it is important to review the physiology of pain and the anatomy of the musculoskeletal system.
Analgesic System
Physiology of Pain
Pain occurs when there is tissue damage in the body. Tissue damage activates pain receptors of peripheral nerves. Nociceptors, the nerve endings that respond to painful stimuli, are located in arterial walls, joint surfaces, muscle fascia, periosteum, skin, and soft tissue. Nociceptors are barely present in most internal organs.[3]
The cause of tissue damage may be physical (e.g., heat, cold, pressure, stretch, spasm, and ischemia) or chemical (pain-producing substances are released into the extracellular fluid surrounding the nerve fibers that carry the pain signal). These pain-producing substances activate pain receptors, increase the sensitivity of pain receptors, or stimulate the release of inflammatory substances (e.g., prostaglandins).[4] Pain can also activate the physiological stress response.[5]
For a person to feel pain, the signal from the nociceptors in peripheral tissues must be transmitted to the spinal cord and then to the hypothalamus and cerebral cortex of the brain. The signal is transmitted to the brain by two types of nerve cells (A-delta and C fibers). The dorsal horn of the spinal cord is the relay station for information from these fibers. In the brain, the thalamus is the relay station for incoming sensory stimuli, including pain. From the thalamus, the pain messages are relayed to the cerebral cortex where they are perceived.[6] See Figure 10.2b for an illustration of how the pain signal is transmitted from peripheral tissues to the spinal cord and then to the brain.[7]
Endogenous Analgesia
The CNS has its own endogenous analgesia system for relieving pain. The CNS suppresses pain signals from peripheral nerves. Opioid peptides interact with opioid receptors to inhibit the perception and transmission of pain signals. These opioid peptides are endorphins, enkephalins, and dynorphins.[8]
See the video below for more information about how pain relievers work.
How Do Pain Relievers Work? by George Zaidan[9]
The Concept of Mobility and the Musculoskeletal System
The concept of mobility is defined as “purposeful physical movement, including gross simple movements, fine complex movements, and coordination; State or quality of being mobile or movable.”[10].
In the mu