What does the body do when it sleeps?
Answer by Arjun Subramaniam:
There are actually a multitude of things that happen when you sleep, including a drop in body temperature, blood pressure, and breathing rate. However, your question seems to imply the reason for why sleep is so essential.
There’s proof that sleep has a profound effect on our emotional, intellectual, and social well-being. Those who regularly get six hours of sleep or less have been shown to live a less happy, shorter life than those who get at least eight hours or more. This is because sleep is responsible for a boatload of important repairs and adjustments that keep us going when the Sun comes up. Let’s dive in, shall we?
Typical sleep consists of about five different cycles, as you can see in the diagram above. The first four stages are characterized by quiet sleep, or Non-Rapid Eye Movement (NREM). The final stage is Rapid Eye Movement (REM).
The first four stages of sleep are correlated with a deepening and slowing of waves associated with brain activity, and almost half of the blood flow is redirected away from the brain and into the muscles to sustain energy. However, brain activity is restored dramatically in the REM stage.
The REM stage is the stage associated with dreaming and is regulated by an area of the brain known as the pons. The pons is a part of the brainstem that regulates REM sleep and dreaming, and facilitates nervous communication between neighboring structures. It has a fascinating part to play in our sleep. When REM sleep kicks in, the pons sends messages to both the thalamus and the cerebral cortex, the areas predominantly responsible for thought processes. In addition, it signals the motor neurons to “turn off”, causing a temporary paralysis and thus preventing us from acting upon our dreams.
REM sleep is an important stage because it is thought to be the time where the brain “arranges” the events and information of the day before, consolidating memory and emotion. This is backed up by the fact that blood flow is increased to areas that are involved with processing memory and emotion.
However, there’s more to sleep than merely brain activity.
Hormone activity also fluctuates wildly during sleep. When we are awake, our body is what we call a “catabolic” state – Our body spends more energy than it takes in. Stimulating hormones like corticosteroids and adrenaline are responsible for this. However, when we sleep, our body slips into an “anabolic” state – Where energy conservation and body repair are higher priorities. Therefore, levels of adrenaline and corticosteroids drop significantly, and the body produces Human Growth Hormone ( HGH ) in larger amounts – a hormone that uses amino acids to catalyze the growth, maintenance, and repair of tissue. This hormone is the reason for the body ‘repairing’ itself during sleep.
Other hormones rise and fall during sleep as well. One hormone secreted at night is melatonin. Melatonin is produced by the pineal gland, and its main function is to regulate circadian rhythms and sleep-wake cycles. Another hormone that is a key part of the sleep-hormone cycle is cortisol, which tends to decrease in the first half of sleep and increase as you prepare to wake up. Cortisol is produced by the adrenal glands and is involved in fear and stress.
Sleep is important for fighting illnesses and aids the immune system. During sleep, the immune system produces a larger amount of certain proteins that fight pathogens. Studies have also shown that sleep can boost your immune system, and sleep deprivation has been proved to reduce the number of white blood cells in your bloodstream – Cells that defend the body against pathogens.
Other rather useful chemicals course through our blood when we sleep. A cancer killer called TNF is produced in greater amounts when we sleep. Research has shown that people who stayed up until 3 AM in the morning had 1/3 the amount of TNF-containing cells in their body, and whatever remained had a greatly reduced effectiveness.
Sleep has a multitude of other functions, including lowering body temperature, repairing skin damage, relaxing muscles, detoxifying blood, and slowing down the digestive system. All in all, sleep is very necessary for our body to recuperate and recover from the events of the day, and disregarding its importance can be very detrimental to your health.