Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (18 page)

Bottom line: possibilities are always wildly, insanely greater than the number of things around us. If each neuron or brain cell could connect with any other in your skull, the number of combinations would be 85 billion! (i.e., eighty-five billion factorial). This is more zeros than would fit in all the books on Earth. And that’s just the zeros—the mere representation of the number, not the actual number. Remember, each time you add just six more zeroes, you’ve made it express a quantity a million times larger than everything that went before that point. The brain’s connection possibilities lie beyond that same brain’s ability to comprehend it.

All this architectural complexity lies in what may seem like an inert three-pound lump of cheese about the same size as a piston on a 1400 cc engine. Because there are no muscles in the skull, and because the brain has barely more density than water, it does indeed appear to be a mushy, unimpressive lump. But its animation is utterly disguised. What makes it vibrant are its relentless electrical activities. Unseen sparks fly everywhere. Each neuron functions on about one hundred millivolts. A tenth of a volt is darned efficient: this operating matrix is less than that of an AAA battery. Even if you add up the brain’s entire energy consumption, it’s a mere twenty-three watts (for a person consuming 2,400 calories daily). Still, the brain uses a whopping 20 percent of the body’s energy despite taking up only 2 percent of the body’s mass. It’s an energy hog. There’s no off switch; the current courses continuously.

The first hints of this electrical activity came from Luigi Galvani in 1791, when he published his work on the electrical stimulation of nerves in a frog. If electricity makes muscles contract, then that’s how the brain must accomplish its commands! The very next year, a fellow Italian, Giovanni Valentino Mattia Fabbroni, suggested that such electrical nerve action must employ chemicals. The whole idea got a big boost eight years later, in 1800, when Alessandro Volta invented the wet cell battery. Here was electricity generated and contained in a self-enclosed way—why couldn’t it be the same in the brain?

Of course it was far more complicated than that. When the 1906 Nobel Prize in Physiology or Medicine was awarded to Camillo Golgi and Santiago Ramón y Cajal for their breakthroughs on the organization of the nervous system, it merely marked an early step in probing a labyrinthine structure that even today is far more mysterious than any other part of the body. But at least at that point we grasped the mechanism by which muscles are commanded to move.

Electricity through a copper wire travels at 96 percent of the speed of light. No such luck when it comes to neural strands. Our body’s neurons come in several different varieties and capacities, but none lets current flow even 1 percent as swiftly as it does through an electric can opener. Yet we apparently don’t need such light-speed cognition to accomplish everyday mental brilliancies, such as bagging the garbage. Our actual maximum operating rate of just 390 feet per second, or less than a millionth of the speed of light, is fast enough to do the job.

This becomes obvious with a quick experiment. Close your eyes and flail a hand rapidly around—over your head, to the sides, anything. You’re always aware of exactly where it’s located, every moment, no matter how quickly you alter its position. Your in-the-moment cognizance of your hand’s location proves that neural electrical signals reach your brain extremely quickly, since only “real-time” information would be useful in such situations. In fact, those impulses travel at 250 miles an hour.

That’s the nerve transmission speed for essential stuff. But what qualifies as “essential”? Fortunately you don’t have to prioritize the relative importance of all the sensory, muscular, pressure, pain, and other signals the brain receives. It’s taken care of, designed and hardwired before you even left the womb. A friend’s carelessly exuberant hand gesture is about to poke your eye? You instantaneously blink and evade. You’re eating and would prefer not to stab yourself with the fork? The positional signals from your fingers and lips coordinate in the moment. On an overnight camping trip, stepping out of the tent barefoot, you tread on a suspicious object that feels an awful lot like a snake. You yank your leg up in an eyeblink. All these reflexes were neurally commanded at 250 miles an hour.

But now stub your toe. Or just remember when you did. It took several seconds to feel any pain. That’s because pain signals travel along separate cables at a low-priority speed of just three miles an hour, or two feet per second. There’s no rush to deliver bad news.

How about thinking? These signals occur at an in-between speed. Neither fastest nor slowest. They slither and branch through the cerebral cortex at seventy miles an hour. The process is speedy enough so that you can make decisions before a separate circuitry—your ego, your sense of yourself—is informed of their completion.

In 2006, the late researcher Benjamin Libet and his team instructed volunteers to push a button the moment they decided which arm they intended to raise and then immediately lift the appropriate arm. Here’s the amazing thing. Researchers watching the subjects’ brain waves could reliably tell which decision they had made up to ten seconds before the volunteers themselves were aware of their choices!

In other words, the brain’s electrical activity performs automatically, like the functions of the pancreas or liver. It makes decisions autonomously. Only a bit later do we realize what’s been decided.

We may have a subjective awareness of choosing. We may say, “I decided to have Chinese food tonight instead of Italian.” But we actually exercised no free will at all. The brain decided on its own through spontaneous electrical connections. None of us has the slightest idea how to control this activity any more than we can manipulate the workings of our kidneys. (If, disagreeing, you now claim that you can personally make choices and that decisions are not automatic, you should know that the construction of that very thought happened autonomously before you even intended to think it or say it.)

All these fast, slow, and intermediate electrical impulses and synaptic connections happen continuously, and their pace is fastest in the morning. We get a break only when the lights go out: the brain operates at a much-reduced level when we’re asleep.

The nervous system’s activity, which peaks between the ages of twenty-two and twenty-seven and starts to diminish thereafter, is of course the control system for myriad other internal motions. The ones we’re most aware of, of course, are the breath and the heartbeat.

Figuring out even basic heart realities didn’t come easily. Despite the knowledge gleaned from dissecting cadavers (during the centuries when this was ethically acceptable), people found the function of the heart and its drumbeat bewilderingly mysterious until rather recently. As long ago as 4 BCE, Greek physicians were aware of heart valves and arteries but still came to wrong conclusions about them. Because blood pools in veins and not arteries after death, Greek anatomists wrongly assumed that arteries transport air throughout the body. Erasistratus, a physician in Alexandria who died in 250 BCE, said that when people received cuts to arteries and bled, it was merely because those “air-filled vessels” were suddenly flooded with blood from the veins.

Later, the famed Greek physician Galen, in the second century CE, did maintain that both arteries and veins contain blood. But he did not think it was the heart that pumped it. Rather, he said, the pulsing arteries did the pumping. The heart merely sucked in blood and served as a kind of repository. Nothing circulated. Blood was created by the liver and then somehow got used up and continually replaced by new stuff.

It wasn’t until 1628 that physician William Harvey finally figured out the circulatory system and explained the reason for that thumping in our chests. (In keeping with science’s hallowed tradition toward pioneers, Harvey was ridiculed for decades.)

The heart beats 2.5 billion times in a lifetime. The five quarts of blood an adult male continuously pumps (four quarts for women) flow at an average speed of three to four miles per hour—walking speed. That’s fast enough for a drug injected into an arm to reach the brain in only a few seconds. But this blood speed is just an average. It starts out by rushing through the aorta at an impressive fifteen inches a second then slows to different rates in various parts of the body.

Normally, liquids such as water speed up when forced to flow through a narrow pipe. Kids like to squeeze a hose to make the water jump farther, to douse their friends. But the opposite happens in the narrow capillaries. Here is where blood flow is slowest.

It’s all part of the oxygen-exchange plan. The reason goes beyond the fact that capillaries are farthest from the heart. Rather, there are so many of them that their cross-sectional area is greater than what’s found in veins and arteries. The blood volume is essentially spread out there.

Lymph fluid moves, too, through its own system of channels, at a low speed of a quarter inch a minute. But air is much livelier. Men and women both normally inhale and exhale about a pint of air—half a quart—twelve or fifteen times a minute. This adds up to a gaseous intake just shy of two gallons a minute. To make this happen, the lungs and diaphragm move in and out an inch a second.

Meanwhile, in the always enjoyable food department, we pop a pastry into the mouth and chew, the lower teeth performing all the motion, rising and falling at the rate of an inch a second. (Studies show that more saliva squirts out when we’re hungry.) Gulp, and down she goes, and now we rely on esophageal peristalsis, a wave of contractions that brings the food stomachward at the speed of three-quarters of an inch per second.

Splash—into the tummy. There it remains for an average of two to four hours.

Next the food is further processed, and its water content removed, as it chugs growlingly through the twenty-foot-long small intestine and then the six-foot-long large intestine. This putrefying mass barrels along at a speed that varies from a foot an hour to a foot every three hours. It depends on the person and also on the food. Stuff with a lot of roughage moves fastest. And fully half the weight of stool is bacteria. Indeed, research in 2012 revealed that about 3 percent of each of us is pure bacteria. We’re each an “us” rather than an “I.”

The entire process—in one end and out the other—can be over in a single day. Or it may require three days. There’s no “normal” here, despite the fact that we all have an opinion about how often we should be going to the bathroom. Some individuals have bowel movements three times a day. Others just once every other day. If you want to speed things up, increasing dietary fiber to twenty-five or more grams a day is the best method. We cannot control the speed at which electricity travels through our neurons, lymph fluid flows through the lymphatic system, oxygen and carbon dioxide change places in the lungs, or blood flows through our capillaries. Nor can we alter the speed of asteroids. It is only in the personal digestive realm that we wish to become “control freaks” and obtain what we imagine to be optimum velocity.

Same with urination. Men and women big and small all pee at the identical average rate—between one-third to one-half ounce per second. Since the mean urine quantity is one to two quarts a day, we are condemned to spend one to two full minutes daily peeing. Rarely more than three. The average woman urinates eight times a day, the average man seven, though up to thirteen times a day is not, believe it or not, considered abnormal. To add it all up, a person who urinates seven times daily will require between nine and twenty-seven seconds to do the job per session.

We thus dedicate an entire month of our lives to this activity.

Men and women blink at the same rate, too. That is, we blink about ten times a minute, or once every six seconds. Staring—as we do when reading—cuts that rate in half. But while extended focusing on one visual task makes us blink less, being tired does the opposite and creates more blinking.

Infants blink just once or twice a minute, for reasons unknown. A possible explanation is that infants need less eye lubrication than adults do simply because their eyes are smaller. Moreover, infants do not produce any eye secretions during their first month of life and thus spare us the heartbreaking sight of crying with visible tears. Infants also get far more sleep than adults do. In any case, blinking steadily increases through childhood and matches the adult rate in adolescence.

Each blink takes just a tenth of a second. But their mysteries linger far longer. People with Parkinson’s disease hardly blink at all, while schizophrenics blink more than people without that affliction. No one knows why.

The instigation of the eyeblink is even faster than the blink itself. The human eye’s reflex, sometimes elicited by nothing more than a puff of air, takes between thirty and fifty milliseconds to travel from the brain to the eye. Better than one-twentieth of a second. Compared to that, voluntary reaction time to a visual signal in a laboratory, even when the subject is keyed up and expecting it, is around one-seventh of a second. In a car, it would then take an additional three-quarters of a second for a driver to move her foot from the gas pedal to the brake. Reflexive actions are the way to go. Conscious choices may be overrated.

Some body motions are even faster than eyeblinks. Within each cell, for example, protein synthesis creates new substances, each with a particular vital function. How fast? A cell’s ribosome can make a disease-fighting protein in ten seconds. Given the millions of cells all simultaneously producing proteins to combat an infection, it’s very long odds against invading bacteria ever gaining a foothold.

Good thing. These armies are often evenly balanced. A colony of bacteria can double its size in nine minutes and forty-eight seconds, and we’ve all experienced boils and other such germ “cities” that temporarily manage to get the upper hand against our defenses.

We’re maximally exposed to disease pathogens when we travel, especially in crowded enclosures such as airliners or buses.