You may be surprised to learn that on average we spend 26 years of our lives asleep. Moreover, we spend a further 7 years trying to get to sleep! But have you ever wondered what your body is actually doing while you’re asleep? Well read on and your questions will be answered.
It was once thought that during
sleep, your body completely shuts down, both physically and mentally. Obviously,
this cannot be the case since, while we sleep, we continue to breathe and carry
out other processes such as cell repair that are vital for life. In fact, overnight
your brain and body work hard to ensure that when you wake up, your body is ready
for action. During sleep your brain repeatedly goes through a cycle of two
different types of sleep, REM (rapid-eye-movement) and non-REM sleep.
The first part of this cycle is non-REM sleep, which is broken down into four stages. Stage one comes between being awake and falling asleep and stage two is light sleep. This is when breathing and heart rate regulate and body temperature drops. Deep sleep makes up the third and fourth stages. You then cycle into REM sleep, the phase where dreaming occurs. The eyes move rapidly behind closed lids (hence the name REM) and your brain waves alter to be similar to those during the day when we are conscious and awake. While the rate of breathing increases, the body becomes temporarily paralysed as we dream. The cycle repeats itself, on average four to five times in one night, but with each cycle you spend less time in the deeper stages three and four of sleep and more time in REM sleep.
Have you ever heard people refer to their natural body clock? That they naturally wake up and fall asleep at the same time every day because their body has supposedly ‘set’ a built-in alarm?
According to research there are two main processes that actually promote this regulated sleep pattern: sleep drive and circadian rhythms.
Much like when it's nearing lunchtime and you can’t wait to dig into a massive slice of cake (no? just me then), your body craves sleep. As the day goes on, your desire for sleep builds, until it reaches a climax where you simply have to shut your eyes. Unlike hunger, where your body can’t force you to ingest food, it can put you to sleep, no matter the circumstances and you have no control over this. When you are exhausted your body even has the ability to engage in what’s called microsleep episodes of one or two seconds when your eyes are open. I have never been one to voluntarily take a nap, but it has been shown that napping for 30 minutes or more late into the day can derail your night’s sleep by decreasing your body’s sleep drive.
Your circadian rhythm is basically a 24-hour internal biological clock that is running in the background of your brain and cycles between sleepiness and alertness at regular intervals. A key function of this clock is responding to light cues, increasing production of the hormone melatonin at night, then switching it off when it senses light. Melatonin is a natural hormone that is produced by the pineal gland in your brain and acts on receptors in your body to encourage sleep.
So, why do we actually need sleep?
It has been proven that sleep significantly impacts upon brain function, notably its ability to accommodate inputs. Too little sleep leaves us unable to process things learnt during the day and reduces our ability to remember it in the future. Researchers also believe that sleep may promote the removal of waste products from brain cells. This process is still carried out while we are awake, just less efficiently. Health risks also rise when people consistently don’t get enough sleep with symptoms of depression, seizures and high blood pressure worsening. During sleep, our bodies try to conserve energy and hence sleep plays a key role in metabolism and people who chronically get fewer than six hours of sleep per night are more likely be obese and diabetic. Immunity is also compromised, increasing the likelihood of illness and infection.
References:
· https://www.webmd.com/sleep-disorders/ss/slideshow-sleep-body-effects
· https://www.sleepfoundation.org/articles/what-circadian-rhythm
· https://www.nhs.uk/medicines/melatonin/
· https://www.sciencedaily.com/releases/2020/04/200422091205.htm
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