In going round the end of the hill I saw a lion sitting on a piece of rock about thirty yards off with a little bush in front of him. I took a good aim at him through the bush and fired both barrels into it. The men called out. “He is shot, he is shot.” Others cried, “He has been shot by another man too, let us go to him.” I saw the lion’s tail erected in anger and turning to the people said, “Stop a little till I load again.” When in the act of ramming down the bullets I heard a shout and looking half round I saw the lion in the act of springing upon me. He caught me by the shoulder and we both came to the ground together. Growling horribly he shook me as a terrier dog does a rat. The shock produced a stupor similar to that which seems to be felt by a mouse after the first gripe of the cat. It caused a sort of dreaminess in which there was no sense of pain nor feeling of terror though I was quite conscious of all that was happening. It was like what patients partially under the influence of chloroform describe: they see the operation but do not feel the knife. This placidity is probably produced in all animals killed by the carnivora and if so is a merciful provision of Creator for lessening the pain of death. As he had one paw on the back of my head I turned round to relieve myself of the weight and saw his eyes directed to Mebalwe who was aiming at him from a distance of ten or fifteen yards. His gun which was a flint one missed fire in both barrels. The animal immediately left me to attack him and bit his thigh. Another man whose life I had saved after he had been tossed by a buffalo attempted to spear the lion upon which he turned from Mebalwe and seized this fresh foe by the shoulder. At that moment the bullets the beast had received took effect and he fell down dead.
David Livingstone (1857). Missionary Travels (pp. 11-12). London: EW Cole.
Scottish explorer Livingstone, in his journey to discover the sources of the Nile, reported what is now known as stress-induced analgesia. Under conditions of extreme stress or in the adaptation to an extreme environmental challenge, an individual’s normal reaction to pain—reflex withdrawal, escape, rest, and recuperation—could be disadvantageous. In a dire emergency, these reactions to pain are automatically suppressed in favor of more useful behaviors. It turns out that we have a piece of software, the analgesia system, that automatically activates in these circumstances, with rather remarkable effects.
The time of such stress-induced analgesia may range from minutes to hours, depending on the nature and severity of the stimulus. There is evidence that stress stimulates both the opioid and non opioid mechanisms of analgesia. Soldiers wounded in battle and athletes injured in sports events report that they do not feel pain.
After being wounded in my tent I rolled out into a foxhole and a North Vietnamese fired three bursts of AK-47 into me. Convinced life was over, I said the Lord’s Prayer, and asked God simply for strength to save my battalion through the night, and that my family be taken care of after death. Suddenly a strange sense of relief came over me, I felt no pain, no fainting, no more terror. A medic crawled to the foxhole amid much weapons firing but I sent him off to take care of other wounded first. He later told me in the hospital that he thought I was near death in the foxhole.
Gen. John A. Wickham (2001). The Battle at LZ Colt of Oct. 10, 1967.
What is happening here? It turns out that we are truly blessed with the analgesia system, a pain suppressing mechanism that effectively shuts off sensory transmission to the brain, so that we are permitted to go about the business of getting out of the gravest danger without the crippling sensations of pain.
The Analgesia System: Technical Specifications
The analgesia system consists of three major components: 1. The periaqueductal gray and periventricular areas of the mid-brain and upper pons surround the aqueduct of Sylvius and portions of the third and fourth ventricles. Neurons from these areas send signals to 2. the raphe magnus nucleus, a thin midline nucleus located in the lower pons and upper medulla, and the nucleus reticularis paragigantocellularis, located laterally in the medulla. From these nuclei, second-order signals are transmitted down the dorsolateral columns in the spinal cord to 3. a pain inhibitory complex located in the dorsal horns of the spinal cord. At this point, the analgesia signals can block the pain before it is relayed to the brain.
The mechanism of pain suppression unfolds through a chemical mechanism. About a dozen opiate-like substances are released at different points of the nervous system, the breakdown products of three large protein molecules: proopiomelanocortin, proenkephalin, and prodynorphin. Among the more important of these opiate-like substances are beta-endorphin, met-enkephalin, leuenkephalin, and dynorphin. The two enkephalins are released in the brain stem and spinal cord, in the portions of the analgesia system, and beta-endorphin is present in both the hypothalamus and the pituitary gland. Dynorphin is released mainly in the same areas as the enkephalins, but in much lower quantities. Thus, although the fine details of the brain’s opiate system are not understood, activation of the analgesia system by nervous signals entering the periaqueductal gray and periventricular areas, or inactivation of pain pathways by morphine-like drugs, can almost totally suppress many pain signals entering through the peripheral nerves. Lucky break for Livingstone and gen. Wickham. And for us.