Eagle-eyed subscribers may have noticed a lack of videos recently. That’s because something fell out of my wife, and we’ve been dealing with the consequences of that ever since. One of the consequences is worthy of a video, which is that I now have a twitch in my eye. Occasionally, my right eye starts to twitch. And it turns out the science of eye twitching is quite interesting. You’ve probably experienced it. Well, maybe you’ve experienced it. It’s quite common to have a twitchy eye now and again. It’s caused by things like fatigue, taking too much of a stimulant drug like caffeine, and having too much exercise. In my case, it’s definitely, not exercise. I’m very good at not exercising. It’s not caffeine either, because I’ve given up caffeine for quite a while now. It’s most likely fatigue, because I’m doing a lot of fatigue at the moment, mainly because this thing that fell out of my wife makes this noise in the night periodically, and it wakes us up. I’ve suggested that maybe we shouldn’t keep it in the house, but you have to, you have to. You can send them to college, but it’s a whole process. It takes about 15 or 20 years. So we’ve set the ball rolling with that, we’re sort of looking into how all that works. In the meantime, how does a twitchy eye work? It’s to do with how neurons work. Neurons are the cells in your body that carry signals around your nervous system. They’re famously long. They’re the longest cells in your body. The longest ones are the ones in your legs. They can be around a meter long. It’s amazing. These single cells that are incredibly long, they join together in chains and networks, and they also join on to your muscles. So you can imagine the end of one of these really long neurons coming up to the flesh of your muscles, and there’s a little gap, there. What happens is, the end of the neuron releases what’s called neurotransmitters, these tiny molecules. Those molecules swim across the gap and they attach to receptors on your muscles. And that attachment of neurotransmitters causes your muscles to contract. So, this release of neurotransmitters from the end of your neurons is usually mediated by signals traveling down your neurons. How does this neuron signaling work? Well, the cells in your body maintain a separation of charge. So, the outside of your cells are slightly positively charged, and the inside of your cells are slightly negatively charged. Some cells are able to temporarily undo this separation of charge. It’s called depolarization. And when a signal travels down your neurons, it’s actually a wave of depolarization. It’s called “action potential”. When that depolarization reaches the end of your neurons, there are these little molecular gates there that respond to the change in voltage by opening. And when those gates open, they allow calcium ions to flow into the end of your neurons. Those calcium ions, once they’re inside your neurons, cause another chemical reaction to take place that opens up these little holes, and it’s those little holes that allow neurotransmitters to flow out, which then travel across the gap, which then attach the receptors on your muscles, causing your muscles to contract. Or at least that’s what’s supposed to happen: a deliberate signal travels down your neurons, causing your muscles to flex. But sometimes, the ends of your neurons can experience spontaneous depolarization. When that happens, the change in voltage opens those little molecular gates, which allows the calcium ions in, which causes a chemical reaction that opens the holes, that allows the neurotransmitters out, that travel across the gap, that connect to the receptors on your muscles, that cause your muscles to contract. And that is why your eye can twitch with no intervention from you or your nervous system. So, why does tiredness cause spontaneous depolarization in the end of your neurons? We don’t know. The answer is we don’t know. Scientists don’t know. Part of the reason for that is it’s not worth researching. Twitchy eye can be a sign of a more serious illness, but the type of twitching you get as a result of fatigue is generally benign. Like, people who experience it don’t suffer. Like, from my point of view, it’s not a problem. It’s only occasional, it’s intermittent, I can get on with my life, and if I really wanted it to stop, I could just get more sleep. This is a good example of something that happens quite often in medicine. Another example is when I was young, I used to experience what’s called Alice-in-Wonderland Syndrome, which is where occasionally, maybe just for a minute or so, you won’t be able to get a good sense of scale of the things around you and even your own body. It used to happen to me in class. I’d be looking at my teacher who’s writing stuff on the board, and it would suddenly seem as if, like, maybe my teacher is massive and far away, or maybe he’s tiny and really close up. I couldn’t tell. There was… I had no sense of an intrinsic scale. Really odd experience. But crucially, it’s not distressing. It just kind of happens and you go, “Huh, that’s interesting and weird.” And then it goes away. It goes away in your teens. It’s very rare for adults to experience it. So yeah, doctors don’t really research it. I was looking into it for it for a show, and I couldn’t find an explanation of why it happens, because no effort is put into finding the answer to that. And that’s interesting, isn’t it? There are all these medical mysteries that we may never find the answer to because we don’t need to find the answer. This is just a short video because I’m catching up on loads of stuff since coming off paternity leave, my self-imposed paternity leave. Actually, I’ve got a few big projects coming up as well. I’m writing my third book. I will tell you about the other two books in due course, but if you want to know about them right now, there’s links in the description. I’ve also got a tour coming up. So I’m really busy coming up, which means there may be some gaps in the future as well. Apologies for that. If you want to make sure that you definitely catch my future videos, don’t forget to click on the notification bell as well, because I know that with sporadic videos, they don’t always appear in your subscription feed. But if you click the notification bell, you will find out about them. But yeah, I mean, I will be back to doing them every two weeks, hopefully fairly soon. Anyway, I hope you enjoyed this video, and I’ll see you next time.