In honor of the fact that I’m rotating through Neurology at the moment, I’m proud to present…
(In case you don’t read Morse Code and were too lazy to google it, that’s what the title says.)
So, nerves are super-cool.
Here’s a picture of one, so you can join me in basking in the coolness of nerves.
What’d I tell you? Coolness personified.
Well, maybe not personified….but if you squint closely, you may find yourself glancing at your neighbor and having a shift in perception, suddenly seeing his shape described only by a network of white, filamentous strands, as if he were a sculpture of spiderwebs….
Well, that’s okay. I also subconsciously judge people based on how easily I could start an IV in the veins on their hands.
(The study of medicine engenders its own special flavors of crazy.)
A nerve cell is called a neuron. That’s the cell in whose coolness we were basking, up there a minute ago.
The job of a neuron is to pass information along, in the form of an electrical signal. (The way this happens is super-cool, and warrants its own post, so stay tuned. For right now, we’ll just talk about how they’re arranged.)
There are three parts to any neuron.
The dendrites (from “dendron”, which means “tree”) are the tree-branch-like projections off of the central cell body, also known as the soma or perikaryon. The dendrites collect impulses from surrounding neurons and send them to the perikaryon. There are usually a lot of dendrites on a neuron, making it easier to collect a LOT of information.
(Dendrites are probably the coolest things in the human body, because they like to rearrange themselves like crazy, making a dynamic structure that allows us to learn and remember things, and adapt to changes and all kinds of other important things like that.)
So, a neuron receives signals through its dendrites. But what if it wants to say something to the other nerves in the area? That’s where the third part of a neuron comes in, the axon.
Axons are incredibly cool structures, too! There’s a conical process on one end of a perikaryon called the axon hillock, and that’s the staging platform that shoots off the axon, a long, cylindrical filament that keeps its diameter for practically its entire length (whereas the dendrites tend to taper off). Axons are responsible for carrying information away from the perikaryon, toward whatever it’s supposed to connect with and talk to. Wherever it is.
(Think about how far away the tip of your toe is away from the end of your spinal cord [it’s a little above the level of your iliac crests, if you remember from this post. ] A nerve axon has to run that entire distance to carry its signals! They’re LONG, man!)
Okay, a little more terminology, then I’m calling this post a wrap and going to bed. And then we’ll get to the REALLY incredibly cool stuff in the next couple of posts.
The connection where nerves can talk to each other (or to muscles or gland cells or whatever) is called a synapse. Axons can form synapses with cell bodies, dendrites, or even other axons. For clarity purposes when describing nerve connections, a neuron sending a signal toward the synapse is called “presynaptic”, and a neuron that receives the signal from the synapse is called “postsynaptic”.
Makes sense, right?
Synapses are oases of awesome in a desert where the sand is made of unabashed coolness. They might get their own post. Or a couple. We’ll see.
Axons are covered with a nifty stretch of jointed insulation, called a myelin sheath. More about that, too. Later.
I know you can’t wait. I hardly can either.
But I’m pushing bedtime as it is.
Man, I’m a geezer already.
But that’s okay. At least you can read this at three in the morning, if you want.
Because your nerves make it possible.
Junqueira, Luis Carlos; Carneiro, Jose. Basic Histology: text and atlas. 11th edition. McGraw-Hill, 2005.
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If you use this as if it were real medical information, I’ll bask in the cool awesomeness all by myself. Didja hear me? ALL BY MYSELF! (So there.)