Welcome to day 2 of NaBloPoMo! Today’s post discusses my favorite subject: our bodies. If you don’t consider yourself a “science person” please stick around because A) this is interesting B) it will make you sound smart someday in the future and C) I promise I will make it fun. It’s a longer post (at least 25 tweets long) but it’s worth it! Let’s go.
1- Exposure Control
Think about this. For all animals, exposure to the environment is both absolutely required for survival and incredibly dangerous. We MUST get food and oxygen from the environment, but we need to protect ourselves from all of the hot/cold temperatures, radiation, toxins, and dangerous aspects of our world. The main way we do this is generally called homeostasis, which I have talked about briefly before, but it essentially means maintaining a cozy internal environment regardless of what’s going on outside. Your skin does a fantastic job of keeping water in (or out), blocking most UV radiation, regulating temperature, etc. Everything inside your skin is air conditioned in the summer, heated in the winter, and packs a light sweater in the spring. Keep in mind that your skin is aided by many other organs/body parts, like your muscles, blood vessels, and organs themselves.
While we are nicely protected from the outside world, that has its downsides. Too much isolation and our ability to gather the necessary materials to survive is severely diminished. Like drinking through a stir straw when you’re really thirsty, you need access to the dangerous world to survive. Our bodies are able to give us both access AND protection. While our skin keeps most everything out, our main avenues for food and air are the intestines and lungs. We absorb these inside of our body, but it helps to think of the lungs and intestines as hollow tubes of “outside” that temporarily pass into our protected “insides”. The lungs have small sack-like structures called alveoli that fill with air and are surrounded by blood vessels. This is where we unload CO2 to breathe out and load up on O2 from outside. By doing this process via millions of alveoli, we have the surface area of a tennis court available for gas exchange in a lung the size of a softball (or youth league football).
Surface area is the key here. Trees have leaves with great surface areas to enable photosynthesis. Microbes need huge surface areas relative to their tiny size to obtain nutrients. Humans have a lousy exterior surface area compared to our size, and we can’t breathe through our skin like frogs. Gas exchange in the lungs occurs like two lines of people trying to simultaneously leave and enter a building through a revolving door. How do you speed that up? Build more doors. Our lungs are so good at gas exchange for the same reason Sonic has great ice in their drinks. The ice is crushed, so it melts more quickly, cools down your drink faster, and keeps it cooler than big old cubed ice. That reason is lots of surface area. Your small intestine is important for absorption of all the delicious food you eat, but it is actually about 22 feet long, allowing you to pull everything you need to survive from your dinner and get rid of the rest.
This is one of the things I have learned in medical school so far that has amazed me. Your body is incredibly efficient. The mechanisms by which we convert food to usable energy are very good. Compare that to a light bulb or car engine, both of which require tons of energy and turn just a fraction of their input to output (with most energy given off as heat). The other amazing part is that when a cell dies, it doesn’t get flushed and ejected overboard. Nope. The cell is degraded, chomped up by other cells that have a striking resemblance to Pac-Man, and it’s parts get sent to other cells for them to use. This efficiency is great for us as a species, but if you are reading this blog you won’t ever need these superpowers. I am sitting about 10 feet from about 30,000 calories worth of food, ready to be eaten. This efficiency is probably left over from the days when people had to work or hunt for food as a survival mechanism. Regardless, we are great at it.
What makes us unique as humans, compared to other animals? Brains! (maybe thumbs). Why do we have huge heads? Brains!
You get the idea. As humans, we have enormous skulls and enormous brains to keep inside them. Everything else comes naturally after that. I could go so many directions with this discussion, but I will stick to the highlights.
Humans give birth to helpless little useless babies, while other species give birth to babies that can walk on their own within hours. Why? Babies have huge heads and need to get out before their heads are too huge. Why? Brains.
Most of our senses are average at best, often terrible, compared to the rest of the animals. Our vision is decent, but many of us would be blind without glasses/contacts. Our sense of smell is bad. Our hearing runs from average to awful. Taste is pretty good, and our sense of touch varies. In addition, our bodies are quite fragile, we are comparatively weak, and we run slowly (but can run for a long time). So how are we at the top of the food chain? Brains!
Compared to any bird (or dragon), our sense of vision is pathetic. What makes us special is that our eyes feed data to an enormous visual cortex that interprets and understands the world around us in a way that is unmatched by any other animal. Without going in to detail about the mechanics of sight, it is interesting to me that we perceive two things incredibly well: contrast and movement.
Compared to any kind of dog, our sense of smell is terrible. Mine is especially terrible, after spending four weeks breathing formaldehyde fumes I really can’t smell much of anything. Our sense of smell is cool because it is unfiltered. Most of our senses (except smell) pass through a structure called the thalamus, an awesome part of the brain that decides what gets your attention and what doesn’t. My elbows have been sitting on my desk while I have been typing for around thirty minutes, but I didn’t realize it until I started typing about it because I was desensitized to it. The thalamus is like a filter/switchboard operator/control tower for the billions of signals fighting for your brains attention. Smells, however, get to skip that step. That’s why you can smell something, even faintly, and BAM!!! You can instantly remember some event from long ago with incredible clarity. Smelling things is like a nostalgia machine. I read a book about World War 2 veterans who talked about certain smells that would bring back powerful memories of terrifying moments in war and could induce panic attacks, even decades later. It’s a powerful sense.
The last thing I want to touch on about our brain is the fact that we don’t really have any idea how it works. We understand what it’s made of (neurons). We know where it is. We also know what certain areas do (mainly by observing what stops working after an accident).What we don’t understand is how our billions of neurons can interconnect and give rise to a supercomputer. Computers are great at math and repetitive logic tasks, but their ability to interpret and assimilate information is no where near the ability of our brain to do the same thing. Our brains also give rise to a personality and emotions, and that doesn’t make sense. When did that mass of neurons develop the ability to love? How did you develop the ability to have compassion on others? That’s where the mystery still is.
As always, thanks for reading. Feel free to comment below or email my face directly at firstname.lastname@example.org