Did you ever burn a finger from a hot spill of coffee, tea, or boiling water? What did you do? Did you run cold water over it? Did the pain go away? It did right? Besides being told by your mother that it was the right thing to do, why else do you think it works..hm...? In this case, cold acts as a natural pain killer!
Let's find out why.
Pain is a primitive experience that we humans share with nearly all animals. Few of us have not suffered the smarting of a bee sting or the cruel persistence of a headache. Although pain offen warns of actual or potential tissue damage, its protective value is difficult to appreciate when we are its victims. It is a sensation we seldom get used to.
Clinically, pain cannot be measured except by some roundabout and inaccurate techniques, such as tapping the painful spot and observing the patient's degree of wincing.
We all have the same threshold for pain; that is, we perceive it at the same stimulus intensity. For example, heat is perceived as painful at 44-46 celsius, the narrow range at which the thermal stimulas begins to cause tissue damage. However, reactions to pain, or pain tolerance, vary widely and are heavily influenced by cultural and psychological factors.
When we say that someone is "very sensitive to pain", we are referring to that person's pain tolerance rather than to the person's pain threshold. Pain tolerance seems to decrease with age, but this, too, may reflect the sociocultural notion that we have to expect pain when we get old. Pain is also modified by emotions and mental state.
P a i n M o d i f i c a t i o n
The extraordinary plasticity of human pain suggests that there must be natural neural mechanisms that can modify pain transmission and perception. It was discovered some time ago that our natural opiates (endorphins) are released within the brain when we are in pain and act to reduce its perception.
Hypnosis, natural chilbirth techniques, and stimulus-induced analgesia are all believed to tap into these natural-opiate pathways. More recently, it was discovered that the opiates also modify pain transmission at the spinal cord level under certain conditions.
According to the Gate Control Theory of pain put forth by Melzcak and Wall in the 1960s:
1. Pain results from a complex pattern of interacting slow (small neural fibers) and fast (large) pain fibers and descending fibers from the brain.
2. The "gate" appears to be in the dorsal horn of the spinal cord.
3. If impulses along the slow pain fibers (small diameter fibers) outnumber inputs along the fast pain fibers, the gate is opened and pain impulses are transmitted to, and perceived by the brain.
4. Stimulation of more fast fibers (large diameter fibers, also touch fibers) closes the gate, inhibiting transmission of pain impulses and reducing pain perception.
When the fast/touch fibers are active, they stimulate the release of endorphins that prevent the transmission of both pain and touch signals to the brain. These events help explain why a massage, or even just rubbing a bumped elbow, can lessen the intensity of pain.
Resouce: Human Anatomy and Physiology, Elaine N. Marieb
So, when we use heat, cold, massage , firm pressure, these are activating the fast fibers which, not only release endorphins, but also stop the transmission and perception of pain, because it never gets to the brain! That's why using them in childbirth works!
Here is a tidbit from Discover Magazine, August 1999:
There is a moment after you stub your toe when time seems to stand still. Even though you immediately sense you may have hurt yourself, more than a second goes by before you feel any pain. That's because messages from sense organs don't get to your brain at the same time.
The speediest signals relay muscle position. They are followed by information about touch and vibration, and then by pain and temperature data. The evolutionary significance of varying signal speeds is unclear, but one theory holds that position and touch arrive earliest because they coordinate movement.
Limb position signals originating inside skeletal muscles race toward the brain at up to 390 feet per second. To catch these at work, close your eyes and wave your arms in the air. You know instantly where your arms are although you can't see them. Touch signals can travel as fast as 250 feet per second. Bringing up the rear are pain and temperature signals, moving as slowly as two feet per second. This disparity explains why there's a delayed sensation of pain when you stub your toe! Discover Magazine, August 1999.
