标签: neuron

I think I may have had an epiphany, but I can’t tell for sure because (a) I can’t spell epiphany and (b) I'm not entirely sure what one is. All I know is that whenever I look in a mirror I feel a sense of awe and wonder that is hard to put into words.   What? No! Don’t be silly, I'm not talking about my legendary good looks. It would be immodest of me to do so, and I pride myself on my humility. I'm talking about something much deeper and more meaningful (as hard as this may be for you to believe).     Actually, this has been building for some time. Out of all the books I've read, and I've read a lot of books, one that truly boggled my mind and that stays with me to this day is Wetware: A Computer in Every Living Cell by Dennis Bray.   Dennis does a masterful job. He starts by describing how a single-celled creature like an amoeba functions, including how it creates proteins and how interactions between different proteins can be used to detect external stimuli, perform "computations," make "decisions," and initiate actions. For example, even though an amoeba comprises only a single cell, it can "crawl" around, hunt for food, and respond to external stimuli like lights and sounds and smells … all without muscles or a nervous system.     Next we move to colonies of single-celled creatures that use proteins to detect each other's presence and to communicate. This leads us to simple multi-celled creatures, in which the different cells forming the organism manage to communicate with each other so as to achieve a common goal.   All of which leads us to the current pinnacle of evolution as we know it, which would be me. Well, you too, of course, but mostly me. (Hey, it's my epiphany we're talking about here!)   My head is buzzing with the amazing things we've discovered, such as how the DNA in our cells actually includes virus DNA. (Approximately 8% of the human genome is made up of retrovirus DNA in our genes.) Or the fact that the number of bacterial cells in our bodies outnumber our human cells by a factor of 10 to 1. (Bacterial cells are very much smaller than human cells. The combined weight of all the bacterial cells is approximately 3 lb in an average adult human being.)   And then we have epigenetics, in which the underlying DNA doesn’t change, but small chemical groups and proteins can attach themselves to the DNA and affect gene expression (i.e., which genes are active or inactive). This is one of the mechanisms behind the way in which our cells differentiate themselves into skin, muscles, nerves, etc. More recently, it's been recognized that an organism's epigenome can be modified by changes in its external environment, and that these changes can passed down to that organism's offspring, all without mutating the underlying DNA. As an aside, I would also highly recommend Life's Ratchet: How Molecular Machines Extract Order From Chaos by Peter M. Hoffmann. One of questions that has baffled philosophers and scientists since time began is how could life arise from lifelessness. Life's Ratchet explains how inanimate matter can spontaneously construct complex processes such as those inherent to living systems.     Have you ever seen animations showing how the molecular mechanisms in cells function? These animations give the impression that everything is orderly and peaceful inside the cell, and that the individual molecular machines are quietly trundling around performing their tasks without a care in the world. In reality, at the molecular level, the inside of a cell is like the heart of a hurricane. The molecular machines have to do things like transcribing DNA and creating proteins in a maelstrom of activity. Once again, Life's Ratchet provides mind-boggling insights into how all of this works.   But, as is so often the case when I start to waffle on about something, we digress … The other day, after quaffing a pint or three of a rather robust beer that was not without a sense of humor, I was standing in front of a toilet having a pee when I came to contemplate the myriad cells forming my bladder.   Whichever way you look at it, these stalwart fellows don’t have the most glamorous of jobs, but they plow on performing their allotted task without complaint for the good of the rest of us (by which I mean the rest of the cells forming my body). This isn’t a one-way street, of course. I think it's safe to say that the cells forming the bladder would look a tad foolish if they weren't backed up by the rest of us in turn.   The point of all this is that each of the trillions of cells in my body (estimates range between 15 and 70 trillion, depending on who you are talking to and how you count them) can be considered to be a separate entity. When you come to think about it, the fact that all of these little rascals manage to play together nicely and march to the same metaphorical drum beat to "make me" is absolutely mind-boggling.   I'm sure that some people simply don’t think about this at all. They just perceive their bodies as being a single entity and focus on other things. Contrariwise, I'm pretty confident that other people would say that I'm stating the obvious.   I guess this is where the epiphany part comes in. I just have an overwhelming sense of wonder about how this all hangs together: the fact that I started as a single cell that divided and divided, and that each of the subsequent cells communicated with others and elected (or were guided) to adopt different functions. I also wonder at the fact that the cells forming my body communicate with the others using such an amazing variety of mechanisms. Cells in proximity to each other communicate by passing proteins back and forth. Other cells forming remote organs communicate with the rest of the body using signaling molecules like hormones.   My nerve cells are also sending electrical impulses throughout my body, including those neurons forming my brain, which I would like to go on the record as saying is one of my three favorite organs.   Am I just rambling on here? Is it just me, or are you also sometimes washed over by a wave of wonder when you come to contemplate how truly amazing I am we all are?