Like is it our brain that’s like “ok sleep time” and we just doze off?
In: Biology
Build up of chemicals in the brain –> Feel sleepy
Feel sleepy –> Close Eyes
Closed eyes –> *Windows Shutdown Noise*
For a more in-depth read, look at Caffeine and its role in blocking Adenosine Receptors in the brain.
We have what is called a circadian rhythm, which is what we refer to as a body clock
We usually let the sun tell us that dark = sleep so when we cut off light our body expects this state
This is why blue light from screens disrupts the rhythm, our bodies interpret the light as daylight and don’t go into sleep mode
Sleep is really fucking complicated so here goes:
You have 2 main sleeping mechanisms, melatonin and adenosine. Broadly speaking both of these chemicals are what build up and make us feel “sleepy”. Melatonin is more closely related to the day-night cycle and adenosine is more closely tied to actually sleeping but you need both for things to work right. As we go through our day, we are receiving all sorts of signals from the world including light into our eyes (shocking I know). That light tells our brain roughly what part of the day it is and how much energy we should have. As it gets closer to night time, melatonin steps in and says “hey you need to be winding down right now”. When we finally close our eyes, we’re no longer receiving light information so the adenosine can now move into the brain to trigger our sleep cycles at night and be cleaned out of our blood. Then we do it all again the next day!
You got it! It is our brain that decides it’s sleep time, but it’s not as simple as just deciding, “Okay, sleep time!” It’s more like a chain reaction:
1. **Sleepy Signals:** Imagine your brain has a little sleepiness meter. Throughout the day, this meter fills up with sleepy signals. These signals come from things like:
* **Time of Day:** When it gets dark outside, our brains start making melatonin, a sleep hormone.
* **Tired Body:** When we’ve been active, our bodies release chemicals that tell our brains it’s time to rest and repair.
* **Quiet Time:** When we relax and close our eyes, our brains receive fewer “stay awake” signals.
2. **Brain Says “Slow Down”:** As the sleepiness meter gets full, our brain starts to slow down its activity. This makes us feel drowsy and relaxed.
3. **Waves of Sleep:** Our brain activity changes into slower and more rhythmic patterns called “sleep waves.” These waves help us fall into different stages of sleep, from light dozing to deep slumber.
4. **Eyes Shut, World Out:** Closing our eyes helps block out light and distractions, which sends a strong signal to our brain that it’s safe to fall asleep.
So, it’s not just one thing, but a combination of signals and changes in our brain that make us fall asleep when we close our eyes. It’s like our brain is saying, “Everything’s quiet, it’s dark, and my sleep meter is full. Time to switch off for a while!”
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