Modern versions of a sabre-toothed tiger

Modern versions of a sabre-toothed tiger

In the last blog: Our old-fashioned stress response, we discussed how our stress alerts can keep us in constant state of alert disproportionate to the situations we find ourselves in. This can lead to problems with our health and well-being.

This time we are sharing a story taken from Anger Kills by Redford and Virginia Williams page 25. This is a very useful book on hostility—one of Redford Williams main subjects of research. The story charts what happens in a person’s body when they suffer irritation and frustration while driving. It makes for a slightly longer post than usual but I think you’ll agree the story is worth it.

An Evolutionary Tale:  Martin Meets Enemies On The Open Road

Martin had at least three reasons to feel satisfied as he pulled out of the parking lot.  The air conditioner in the company car was already making a dent in the eastern North Carolina July heat that had built up while he was making his sales rounds in the county hospital.  The ten automatic blood-pressure monitors he had persuaded the operating room supervisor to order put him over his quota for the quarter – the bonus would come in handy when Betty took the boys to buy their school clothes.  And with a little luck he’d make the Raleigh beltway before rush hour, getting home in time for dinner with his family.

Martin’s good mood lasted until he was accelerating through the last outskirts of town.  He loathed the prospect of the two-lane blacktop, which stretched for forty miles ahead until it widened to four lanes east of Raleigh.  “Those damned slowpokes are sure to be out there making it hell for the rest of us!” Martin thought.

He mashed the gas pedal and enjoyed the surge of the V-8 quickly bringing the speed up to his usual six to seven miles above above the fifty-five-miles-per-hour speed limit.  All was fine for the first ten to fifteen miles, but then up ahead loomed a large, slow-moving truck laden with pulpwood, an all-too-common road hazard in this part of the state.

“At least there’s only one car behind that damned truck now-if he’ll go ahead and pass,” Martin mused, “I can scoot by and not get stuck in another convoy.”

But the other car-an older sedan, much in need of a washing-didn’t pull out, even though Martin could see a clear road ahead of the truck. “Asshole!” Martin barked toward the drier in the sedan.  “Move it while there’s room!”

As Martin drew closer, the sedan continued to sit there behind the truck, apparently happy to dawdle along at fifty-three miles per hour. Martin flashed his lights several times, exhorting the other driver, “C’mon, dummy, pass now!”.

Unable to stand the delay any longer, Martin eased to the left, saw open road ahead, and pulled out at full power to pass both the slow-moving car and the truck.  Even before he made it past the sedan, he realized his mistake-a rapidly approaching oncoming car had rounded the curve ahead.  Quickly turning on his right turn signal, Martin looked to pull back in behind the pulpwood truck.

But the fellow in the car to his right wasn’t slowing down to let him back in!  In fact, he actually speeded up so that Martin had to slam on his brakes and drop back.  He barely manoeuvred back into the right-hand lane before the oncoming car streaked past, lights flashing and horn blasting.

“Dumb bastard!” Martin raged.  “Too chicken to pass the truck himself, but not considerate enough to let me back in when I try to pass!”

Even though he’d been able to keep his promise to Betty to lay off the cigarettes this whole trip, Martin found himself rummaging through the glove compartment and pulling out the reserve pack he kept hidden there.  As he pulled the smoke into this lungs his rage began to subside, but not completely.  He was tempted to take down the license number of the slow-moving car and turn it in with a complaint for reckless driving.

As these thoughts percolated through Martin’s mind-somewhere in his left cerbral cortex-they sent out a wake-up call to a group of hypothalamic nerve cells deeper within his brain.  These cells in turn sent messages to the way station even further down in the base of his brain, where they caused outgoing nerves to signal the adrenal glands atop each of Martin’s kidneys to pump large doses of both adrenaline and cortisol into his bloodstream.

“Murderer!” Martin seethed.  “At least a potential murderer, that’s what the driver was.”

As the adrenaline reached Martin’s heart it began to pound harder and faster.  If his blood pressure registered this high in his doctor’s office, he’d be on blood pressure pills.

“That bastard belongs in jail!”.

At the same time, the activated hypothalamic emergency centre stimulated sympathetic nerves to constrict the arteries carrying blood to Martin’s skin, kidneys, and intestines, while the adrenaline was causing the arteries to his muscles to open up wide.

All of these biological changes Martin experienced on the two-lane highway would have been very useful if he, like his ancestors of more that two million years ago, were being attacked by a sabre-toothed tiger.  A person in danger of being slashed by tooth or claw has no need to worry about digesting a meal or wasting precious bodily fluids on urine formation.  It’s also better to keep the blood away form the skin on the body surface.  But pump that blood in buckets to those muscles that are so essential for “fight or flight!”.

The extra cortisol now in Martin’s bloodstream prolonged and amplified the adrenaline effects on his heart and arteries-very useful, too, if one is running away from a sabre-toothed tiger or trying to keep another male in your hunter-gatherer group from stealing your mate.

Meanwhile, the fired-up cells back in his hypothalamus were shutting off Martin’s parasympathetic nervous system so that the blood-pressure rise and other adrenaline effects were not quickly terminated by the parasympathetic “calming response” but continued to keep his circulatory system churning away.

The adrenaline and cortisol also caused his immune system to go into a holding pattern-again, not a bad idea in situations where serious bodily harm is a real possibility.  If you’re slashed and bleeding, you don’t want your immune system to start making antibodies to your own tissues.

As the angry thoughts and feelings continued, Martin’s heart also continued to pump out blood far in excess of the needs of his body, which was simply sitting there in the car heading back toward Raleigh.  Indeed, Martin’s body sent messages back up to his brain about the bodily effects-pounding heart; sweaty palms; deep, rapid breathing-of the massive adrenaline surge.  These messages reinforced his perception that real danger must be close at hand.

Martin’s blood pressure rose quickly, and, somewhere on the smooth inner lining of one of the coronary arteries that supply blood to his heart muscle, a patch of endothelial cells was eroded by the rapidly swirling currents of blood rushing past-much like a river bank when the stream is at flood.

To make matters worse, Martin’s platelets-tiny subcellular clotting elements circulating in the blood-hurried to the damaged spot of the artery.  Two million years ago this would have been normal and useful, for if the artery had been slashed by the sabre-toothed tiger, the platelets sticking to the spot would seal the hole and stop the bleeding.

Only there was no tiger, and the artery wasn’t slashed.  Nevertheless, just as it has in humans since time immemorial, the adrenaline stimulated more of Martin’s platelets to clump at the scratched arterial surface, where they released some chemicals that stimulated the muscle cells in the artery wall to migrate to the inner surface, where they would grow and multiply.  Other blood cells called macrophages were summoned to the scene to gobble up the injured tissue and debris.

The adrenaline also stimulated Martin’s fat cells to empty their contents into the bloodstream – to provide energy for the effort he would need to exert had a real emergency occurred.  Because he really wasn’t burning up this fat in order to escape from the tiger or fight a rival trying to steal his mate-but just sitting there fuming in his car-Martin’s liver converted the fat into cholesterol.  This excess cholesterol was absorbed into the clump of platelets and macrophages on the scratched artery, and some of it even made its way into the artery wall.

Let’s look for a moment into Martin’s future.  We see many more such arousals of his fight-or-flight response, many of them stimulated by nothing more than his own cynical expectations that others will be mean and selfish, rather than by what they actually do.  Each time this happens, the scratched spot inside his coronary artery will be damaged anew.  And each time, the cholesterol formed from the unused fat that pours into his bloodstream will accumulate in the macrophages and the smooth muscle cells that have been drawn to the spot.

For reasons still not fully understood, these cholesterol-filled “foam cells” don’t clear out but just sit there.  Over the course of a few more years, they mature into an arteriosclerotic plaque that nearly blocks off the flow of blood into the coronary artery entirely.  A day will come when this plaque is traumatized again, perhaps one morning when the traffic on the way to work really annoys Martin.  The platelet plug formed this time will be so big that it completely closes off the remaining small opening in the artery.  A clot will form, and the life-sustaining blood will no longer be able to pass through to nourish Martin’s heart muscle.  The blood-starved heart muscle downstream will be injured as a result; a portion will die.  When this happens, Martin’s heart muscle.  The blood-starved heart muscle downstream will be injured as a result; a portion will die.  When this happens, Martin will have become one of the 500,000 – plus Americans who have hearts attacks each year.

But all this is several years off.  Let us return now to the present, where we note that Martin does arrive safely at his home in a Raleigh suburb—actually, no more that fifteen minutes later that would have been the case if he had succeeded in passing the slow-moving car and the pulpwood truck.  As he comes through the door he yells at one of the boys for having left a bicycle in the drive.  Betty decides to overlook the smell of cigarettes on his breath—better to remind him later of his promise to quit.

Instead of sitting with Betty to share the good news about his sales, Martin pours himself a double scotch.  It’s gone in under five minutes, and he pours another.  Feeling somewhat calmer, he has two extra servings of lasagne for dinner.  Somehow, this helps him feel better.  About 11:00 that night, still feeling restless, he raids the freezer for a big serving of ice cream.  Finally he crawls into bed beside Betty, who fell asleep two hours before.  After another half-hour of tossing, Martin drifts off into a fitful sleep.

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