How light tells you when to sleep, focus and poop

Light exposure is crucial for our physical and mental health, as this and future articles in the series will show.

But the timing of that light exposure is also crucial. This tells our body to wake up in the morning, when to poop and what time of day it can best concentrate or be alert. When we are exposed to light, our body temperature, blood pressure and even chemical reactions in our body are also regulated.

But how does our body know when it’s time to do all this? And what does light have to do with it?

What exactly is the body clock?

One of the most important roles of light is to reset our body clock, also known as the circadian clock. This works like an internal oscillator, similar to a real clock, ticking away as you read this article.

But instead of being heard ticking, the body clock is a network of genes and proteins that regulate each other. This network sends signals to organs via hormones and the nervous system. These complex loops of interactions and communications have a rhythm of approximately 24 hours.

In fact, we don’t have one clock; we have trillions of body clocks throughout the body. The central clock is located in the hypothalamus area of ​​the brain and every cell in every organ has its own cell. These clocks work together to help us adapt to the daily cycle of light and dark, tailoring our body’s functions to the time of day.

However, our body clock is not accurate and works on a rhythm of about 24 hours (average 24 hours and 30 minutes). So every morning the central clock must be reset, which signals the start of a new day. That is why light is so important.

The central clock is connected directly to it light-sensitive cells in our retina (the back of the eye). This daily resetting of the body clock with morning light is essential to ensure that our body functions properly, in harmony with our environment.

At the same time, eating food also plays a role in resetting the body clock, but this time it concerns the clock in organs other than the brain, such as the liver, kidneys or intestines.

So it’s easy to see how our daily routines are intimately linked to our body clocks. And in turn, our body clocks determine how our bodies work at set times during the day.

Let’s take a closer look at sleep

The naturally occurring brain hormone melatonin is linked to our central clock and makes us feel sleepy at certain times of the day. When it is light, our body stops producing melatonin (its production is inhibited) and we are alert. Closer to bedtime, the hormone is produced and then secreted, making us feel sleepy.

Our sleep too partially checked Through our genesthat are part of our central clock. These genes influence our chronotype – whether we are a ‘lark’ (early bird), ‘night owl’ (late riser) or a ‘dove’ (somewhere in between).

But exposure to light at night, while we’re actually sleeping, can have harmful effects. Even weak light from light pollution can affect our health heart rate and how we metabolize sugar (glucose), can lead to psychiatric disorders such as depression, anxiety and bipolar disorder, and increase the overall risk of these premature death.

The main reason for these harmful effects is that light disrupts the body clock ‘at the wrong time’, and these effects are more pronounced in ‘night owls’.

This ‘wrong’ exposure to light is also linked to the harmful health consequences that we often see in people who work night shifts, such as an increased risk of cancer, diabetes and heart disease.

What about the intestines?

Digestion also follows a circadian rhythm. Muscles in the colon that help move waste are more active slower during the day and at night.

The most significant increase in colonic movement begins at 6:30 am. This is one of the reasons why most people feel the urge to poop in the early morning instead of in the evening.

The day-night rhythm of the intestines is a direct result of the functioning of the intestines’ own clock and the central clock (which synchronizes the intestines with the rest of the body). It is also affected by when we eat.

What about focusing?

Our body clock also helps control our attention and alertness by changing the way our brain functions at certain times of the day. Attention and alertness levels improve in the afternoon and evening, but decline during the night and early morning.

Those fluctuations influence on performance and can lead to reduced productivity and a increased risk of errors and accidents during the less alert hours.

So it is important to perform certain tasks require our attention at certain times of the day. That includes driving. In fact, disruption of the circadian clock at the start of daylight saving time – when our bodies have not had a chance to adapt to the changing clock –increases the risk of a car accident, especially in the morning.

What else controls our body clock?

Our body clock influences many other aspects of our biology, including:

• physical performance by monitoring the activity of our muscles
• blood pressure by controlling the system of hormones involved in regulating our blood volume and blood vessels
• body temperature by controlling our metabolism and our level of physical activity
• how our bodies deal with medications and toxins Through controlling enzymes involved in the way the liver and kidneys remove these substances from the body.

Morning light is important

But what does this all mean for us? Exposure to light, especially in the morning, is crucial for synchronizing our circadian clock and bodily functions.

In addition to giving us a good night’s sleep, increased exposure to morning light also benefits us mental health And reduces the risk of obesity. Increasing our exposure to morning light – for example by taking a walk or eating breakfast outside – can directly benefit our mental and metabolic health.

However, there are other aspects we have less control over, including: the genes that control our body clock.

This article is republished from The conversation under a Creative Commons license. Read the original article.