The Body Electric

We are juiced. From head to toe, miles of membrane shuttle electric charges through the body. Impulses pour in to the brain from eyes, ears, nose, mouth, and skin as electric translations of what I see on this screen, the feeling of the keys at my fingertips, the tapping sounds; then out from the brain through the wires to the muscles in my hands and fingers to type the s e  l e t t e r s.

Simple nerve systems appeared in early jellyfish and other sea creatures about 500 million years ago.  Loose nets of nerves responded to light and the touch of other creatures as these swimmers captured smaller fish and dodged bigger ones.

Much earlier, in the first fully developed cells, neurons began to evolve from membranes. A membrane, in Wikipedia’s words, is “a selective barrier; it allows some things to pass through but stops others.” A cell’s membrane helped the cell manage the salt levels inside the cell as it floated through the salty ocean. And since the salts of sodium, potassium and calcium consist of atoms with a positive or negative charge, the pores in membranes became gates that opened and closed to control the electrical potential across the membrane itself.

As animals evolved, such membranes lengthened into neurons with conductive axons, the “wire” of the nerve cell. In us, the longest axon runs down the length of each leg, branching as it goes. The shortest axons, fractions of a millimeter, fill our heads by the billions.

Neurons in the brain (Wikipedia)

Neurons in the brain

The axons don’t carry an electric charge in the way that a wire carries electricity or a lightning bolt of electrons crashes to the ground. Instead, think of the wave at a sports stadium, where groups of fans stand up, throw their hands in the air, and sit down in a spontaneous sequence that moves through the rows. A nerve impulse moves down the axon in a similar way, charged atoms crossing through opened pores from one side of the membrane to the other and then quickly back again while the “wave” of the electric charge moves along.

The impulse never varies in strength. It is either on or off, moving or only ready to move. There are no drops in the current, no power failures, no biological surge protectors needed. If a muscle must contract to move a load, the nerve signal, always at the same strength, simply repeats rapidly enough so that the muscle cells remain contracted.

At both ends of the axon, where the impulse begins and ends, devices of various kinds translate between the electrical charge and other structures. In the ear, sound waves cause small hairs to vibrate and set off the impulses that we hear as “hello.” In our eyes, light causes molecular changes that trigger the impulses to the brain to form the image we recognize as a chair. Where a neuron terminates at a muscle cell, the final “wave” triggers chemicals that start the muscle’s contraction.

We barely notice all this wizardry. Compared to the breath that we can feel and the blood we can see, our circuitry is undetectable. But if we’ve been shocked by a faulty toaster or we suffer from numbness or irregular heartbeats, we’ve glimpsed what can go wrong.

In another way, though, we are always aware of the electricity in us. Notice the faint tingle that is always present in our limbs and head. It’s a sense of animation, a potential, an ability to move a muscle, look around or think a thought at any time. That tingly readiness is, essentially, our neurons at the ready. It’s a reminder that we’re alive.

New Thinking About the Origin of Life (2): Catalysts and Containers

Jeremy Sherman’s book, Neither Ghost Nor Machine: The Emergence and Nature of Selves, describes Terrence Deacon’s theory of how, from lifeless chemical reactions, self-generating arrangements of molecules might have emerged that led to the first living cells. In the previous post I summarized Sherman’s description of purpose and self-ness as the distinguishing features of not just humans but of all living things. All living cells—as selves—share three abilities: self-repair, self-protection, and self-reproduction. Ordinary chemical reactions lack all three and soon fizzle out, their components lapsing into the disorder that overtakes any reaction that cannot sustain itself long enough. What kinds of reactions could come together to hold off such a burn-out?

Catalysts are part of the story—perhaps even the heroes. Catalysts are substances that speed up a chemical reaction without themselves being altered. Sherman compares catalysts to a wheelbarrow used “for hauling gravel over a hill. Without the wheelbarrow, it takes a lot of work to move the gravel. With it, the gravel moves more efficiently and the wheelbarrow isn’t altered in the process. Its presence therefore reduces work, haul after haul” (140).

An example of catalysts that we put to use most days is the catalytic converter built in to the exhaust pipes of our cars. The converter consists of metal plates coated with a catalyst such as aluminum oxide that converts the engine’s exhaust pollutants that flow over the catalyst into carbon dioxide and water that come out the tailpipe. The catalyst itself is never used up.

Now imagine this: chemicals A and B, helped along by catalyst X, react to form a compound. Catalyst X itself is not used up; it continues to speed the reaction as long as A and B are available. Now assume that the compound produced by this reaction is X itself, the same chemical, Catalyst X, that boosted the reaction. The result? The total amount of X—the original amount that never diminishes plus the added amount produced by the reaction—increases rapidly. This is autocatalysis (pronounce autocaTALysis), a sequence, a chain of reactions, in which a chemical reaction happens to produce the catalyst that stimulates the reaction itself. Autocatalysis takes many forms, with different reactions producing various compounds and catalysts but always coming full circle to add to the existing supply of catalyst.

Now “Imagine,” Sherman writes, “autocatalysis occurring within a container. It would look a little like a very simple cell—a chemical population explosion occurring within something like a cell membrane….Imagine that one of the autocatalytic by-products was a capsid molecule [a protein that forms a shell, usually around a virus],… yielding a container” (152). Deacon calls these proto-cells autogens—self-generators.

Still, container or not, even autocatalysis winds down when the A and B that fuel it are used up. The key to Deacon’s theory is that another reaction takes place to constrain the autocatalysis and resupply it. Moreover, this second reaction would also fail at some point were it not also constrained in turn by the renewed catalytic cycle. The second law of thermodynamics always wins if a reaction or the structure of something is left to itself; things come apart, break down, disperse. But if two reactions are such that they stop each other and resupply each other before one fizzles out, the second law must come back another day.

The formation of the container is the second reaction here and the container will sooner or later break apart, perhaps from an event as simple as a large molecule bumping into it. When that happens, the capsid molecules that form the container will drift away, the catalysts inside the capsule will come in contact with new reactant molecules in the environment, the reactions will produce more capsid molecules which will in turn form containers around new clusters of reactants and catalysts. In this way, at this stage in their cycle, the autogen as a whole has repaired and renewed itself. The cycle sounds complicated, but the following video illustrates it well.

Terrence Deacon, Origins of life, Autogen Demonstration – YouTube

A five-minute animated video about Deacon’s autogens (“autocells” in the video).






This cycle of closed container/open container/closed container may seem far-fetched until we realize that we see variations of it throughout the living world. As Sherman points out, the cycle parallels the seasonal sequence of a protected seed opening to release molecules that regenerate and arrange themselves into plants that in turn produce new seeds. Such a cycle is, in fact, the identity of a plant. What we call “a sunflower isn’t the seed phase or the plant phase but the complementary tendency to alternate between the phases. The autogen is even a little like the chicken and egg. Regardless of which comes first, we identify the pair of alternating phases as a self within a lineage of selves” (165).

Among non-living things, fires burn out, even rocks erode. But autogens are able to postpone the disorder and the dispersal that characterizes lifeless matter by building a cycle of reshuffling and rearrangement. And autopens evolve. As certain varieties come to outnumber others, some capsules become more likely to open in the presence of  fresh reactants than in their absence, improving the odds of survival. Others carry around a template, an early kind of DNA, that preserves a particular sequence of, for example, a successful catalytic reaction. In such ways, “selves resist nonexistence” (193). And while the simplest autogens are not living cells, with each change that makes them more efficient and persistent, they get closer.


Breath: Divine Gas In a Smart Body

The word breath most often refers to the air we pull in to and pump out of our lungs (or to the action of doing so) as in “Take a deep breath.” But we also give the same word loftier qualities in phrases such as “the breath of life” and in practices like yoga that view the breath as a source of health and peace. Other traditions and languages also have words for breath in both these ordinary and spiritual senses, such as Latin spiritus, Hebrew ruach, and Chinese qi.

breath spirit (

But what about the breathing body itself? Unless we are wheezing or short of breath, we usually take the smooth coordination of our lungs, diaphragm, membranes, and blood cells as unremarkable. But let’s refocus our wonderment for a moment. The air is, when you come down to it, just a mix of gasses, but our body’s ingenious respiration of them is a process to appreciate.

We breathe in air because it contains one gas that we must have: oxygen. We know that. Less familiar, though, is the step-down system that has evolved to make the most of the fact that, like all gasses, oxygen spreads out from wherever there is more of it to where there is less of it. Thanks to this step-down dispersal and our flowing  blood, we move oxygen from the air outside of us to every cell that is waiting for it, all several trillion—that’s 000,000,000,000—of them.

Why oxygen? Its electrons are arranged in such a way that it interacts eagerly and often with other elements. It’s a potent extrovert. The body’s cells may get their nourishment from food molecules but not unless they also have oxygen handy to break those molecules down. That would be like our eating dinner without any acid in our stomach to digest it. No nourishment. Without oxygen, cells go hungry.

But a little oxygen goes a long way. The numbers surprised me. Only about twenty percent of the air that we breathe is oxygen. The rest is nitrogen and a percent or two of other gasses. And of that twenty percent of oxygen that we inhale, we actually use only about a quarter of it. The rest goes out again. Our inhalation is twenty percent oxygen; we exhale fifteen percent.

Once it is in our lungs, oxygen must get across the lung’s membrane to the blood stream that will move it around the body. The amount of oxygen in the lung might not seem like much, but it is more than remains in the oxygen-depleted blood that is returning towards the lungs through the veins. So the new oxygen steps down across the thin membrane to the empty hemoglobin molecules in the blood cells for the ride to the rest of the body.

As this convoy of oxygenated blood flows near, say, a finger, the oxygen detaches from the hemoglobin, steps down once more across a membrane to a cell itself, and goes to work on the food particles. In the process, extrovert that it is, oxygen combines to form unusable carbon dioxide, crosses the cell membrane back out to some empty passing hemoglobin that just dropped off new oxygen elsewhere, rides the vein back to the lungs, gets off again, and is exhaled back out to air. Like riding the bus you took to work back home at the end of the day.

I argue for the wonderment of a distribution system that pulls in air-borne oxygen in an endless rhythm, arranges for it to disperse itself across strategic membranes, loads it on to the blood for transport to a million million cells that it will help nourish, after which it returns the way it came in. Our stunning respiration makes oxygen look good—even divine.