Gate control theory and management of pain
Gate control theory and management of pain
Gate Control Theory
The gate control theory (GCT) was proposed in 1965 to explain the relationship between pain and emotion. Melzack and Wall (1982) concluded that pain is not just a physiologic response but that psychological variables (i.e., behavioral and emotional responses) influence the perception of pain. According to the GCT, a gating mechanism occurs in the spinal cord. Pain impulses are transmitted from the periphery of the body by nerve fibers (A, delta, and C fibers). The impulses travel to the dorsal horns of the spinal cord, specifically to the area of the cord called the substantia gelatinosa. The cells of the substantia gelatinosa can inhibit or facilitate pain impulses that are conducted by the transmission cells. If the activity of the transmission cells is inhibited, the gate is closed and impulses are less likely to be conducted to the brain. When the gate is opened, pain impulses ascend to the brain. Similar gating mechanisms exist in the descending nerve fibers from the thalamus and cerebral cortex. A person’s thoughts and emotions can influence whether pain impulses reach the level of conscious awareness (Helms & Barone, 2008; Litwack, 2009).
The gate control model ( Figure 15-5 ) differentiates the excitatory (white circle) and inhibitory (black circle) links from the substantia gelatinosa to the transmission cells as well as descending inhibitory control from brain stem systems. The round knob at the end of the inhibitor link implies that its action may be presynaptic, postsynaptic, or both. All connections are excitatory, except the inhibitory link from substantia gelatinosa to the transmission cell (Melzack & Wall, 1982).
As mentioned in the case study, it is believed that pain medication has an effect on the gating mechanism. If pain medication is administered before the onset of pain (i.e., before the gate is opened), it will help keep the gate closed longer and fewer pain impulses will be allowed to pass through. The greater the degree of pain, the greater the number of pain impulses passing through the gate. If fewer pain impulses are allowed through the gate, the person will experience less pain. If the gate is allowed to open completely, a higher dosage of pain medication is required to close the gate. Therefore, in theory, prevention and management of pain are linked to keeping the gate closed.
