 We are often told not to use phones at night. It affects our sleep. Why do we say that? Well, in this video, we're gonna find out. All right, so in this video, we're gonna focus on a very small section of the brain, which is called the pineal gland. Let me write that. This is called the pineal gland. And it's called so because, and I have a photo over here of a pine cone. It looks kind of like a pine cone and that's why it's called the pineal gland. And so we wanna learn the function of the pineal gland. So what does it do? Well, first of all, since it's a gland, it should tell us that it secretes hormones. All right, so which hormone does a pineal gland secrete? Well, it turns out it secretes a hormone called melatonin. And melatonin is often also called the sleep hormone. The sleep hormone. So how does it help us sleep? Imagine the sun has set, it's dark everywhere. So the amount of light entering your eyes is reduced, your brain detects that. And it signals the pineal gland to start secreting melatonin. So during the nighttime, your melatonin levels start increasing in your body. And just like with any hormone, these melatonins will go and bind to the receptors. And turns out that your brain itself has a lot of melatonin receptors. Even your eyes have a lot of melatonin receptors. And when they bind to it, they basically tell the body to prepare for sleep. So your neural activity changes, it reduces probably. Your eyes is being signaled to start shutting down. And that's why you feel sleepy. And towards when it's like, when it's nighttime and it's about, when you're about to sleep, that's when you can imagine that the melatonin levels are very high in your body. And your body has prepared for sleep. And then you go to sleep. Then in the morning, what happens? There's a lot of light that gets shun in your eyes. That signals the brain and brain tells that, oh, it's morning time. And so it tells the pineal gland to start, stop releasing melatonin. And therefore during the morning time, the melatonin levels in your body has gone down. And as a result, your body is now back to being awake. And this is how melatonin helps in regulating our sleep cycle or the circadian rhythm. Now, does this help you answer the initial question that we asked? Why is it that we shouldn't use phones at night? Can you pause and try? Well, when you're using phones at night, a lot of light is entering your eyes. So your brain might get full into thinking that, hey, there's a lot of light coming, which means maybe it's daytime. So it can actually signal the pineal gland at night to stop releasing melatonin. So in the nighttime, the melatonin levels could go down and that could make it harder for you to sleep. And that's why we are usually advised to not have a lot of light around a few hours before the sleep time so that your body can do its thing, whatever it was evolved for. So that at nighttime, you have a lot of melatonin levels and you can easily sleep. Also, melatonin helps in other things like it helps in your metabolism. Turns out that it also affects the pigmentation of your skin. Pigmentation. And in fact, pigmentation. In fact, you might know that the pigmentation in your skin is called by melanin, is caused by melanin. Now, do you think it's a coincidence that melanin sounds so similar to melatonin? No, it's not a coincidence. In fact, when we discovered melatonin, the way we discovered it is we found that the secretions of the pineal gland affects the pigmentation of the skin. And that's how whoever discovered that, I forget his name, but whoever discovered that, they thought of keeping a name for that secretion very close to melanin and therefore they named it melatonin. Okay. Also, it turns out that melatonin affects menstrual cycles. And finally, it turns out melatonin is also an excellent antioxidant. And that's probably it. So to quickly summarize, when there is less light around during the nighttime, your brain signals the pineal gland to start secreting melatonin. Melatonin levels increase in your body. That prepares your body for sleep. And when there's a lot of light entering into your brain, into your eyes, the brain signals the pineal gland to reduce secretions of melatonin. So stop secreting melatonin. The melatonin levels go down in your body and that prepares your body to be awake.