What Happens To The Human Body While Sleeping?

Human spend about one-third of their lives asleep. Sleep is not merely rest, but a process for restoration of all body organs to function properly.


When you sleep, the body undergoes repair and detoxification. Sleep also helps the body to produce immune system to fight infection and keep you healthy.

Poor sleep patterns are linked to numerous health problems, including depression, high blood pressure, obesity, irregular hormone production, decreased in concentration and memory – and those who sleep less than six hours a night have a shorter life expectancy than those who sleep for longer. So, sleep has a profound effect on our emotional, mental, and physical well-being.

Here are few things that happens to your body while you sleep, according Dailymail.co.uk.


Sleep may seem to be passive and dormant state, but even though activity in the cortex drops by about 40% while we are in the first phase of sleep, the brain remains highly active during later stages of the night.

During the first stage of sleep, brain waves are small undulations. During the second stage, these waves are interspersed with electrical signals called sleep spindles, the small bursts of activity lasting a few seconds and make the situation calm.

In the third stage, the brain waves continue to deepen into large slow waves. The larger and slower the brain wave, the deeper the sleep. At stage four, 50 percent of brain wave slowing. At this point, 40 percent of normal blood flow in the brain was transferred to the muscle to restore energy.

This is the stage associated with dreaming and is triggered by the pons – the part of the brain stems that relay nerve impulses between the spinal cord and the brain – and neighbouring structures.

Body temperature

Just before we go to sleep, our core body temperature drops. This to ensure a good night’s sleep. Studies have found that insomniacs tend to have a warmer core body temperature than normal sleepers just before bed, which means they struggle to fall asleep.

The eyes

On first falling into semi-consciousness, the eyes roll. But as we move into deep sleep, rapid eye movement (REM) occurs, with the eyes moving quickly for up to 30 minutes at a time, repeating every 90 minutes. Much of our dreaming happens during REM and despite our eyes moving intensely, our bodies are extremely relaxed which helps us stay asleep.


During our waking hours, the body burns oxygen and food to provide energy. This is known as a catabolic state, in which more energy is spent than conserved, using up the body’s resources. But during sleep, we move into an anabolic state, in which energy conversion for improvement and growth. At this stage, the body begins producing human growth hormone (HGH) and melatonin.

HGH encourages growth, maintenance and repair of muscles by facilitating the use of of amino acids. While melatonin is a hormone produced to help people sleep.

Blood pressure

When we sleep, the heart rate goes down by between 10 and 30 beats per minute. This produces a decline in blood pressure, which occurs in restful sleep. The cells and tissues that break down to produce toxic also become less active during sleep. This gives an opportunity for damaged tissue to be rebuilt.


During sleep, throat muscles relax so that the throat gets narrower each time we inhale. Snoring occurs when the throat is narrowed to a slit and parts of the airway vibrate because of a resistance to breathing. Air is forced through the narrow air passage, causing the soft palate and uvula to vibrate.

Those who snore are more likely to have poor muscle tone in the tongue and throat, which allows the tongue to fall backwards into the airways. Being overweight or having large tonsils and adenoids also contribute to snoring.


Saliva is necessary to lubricate and moisten the mouth. But during sleep, salivary flow decreased, causing dry mouth in the morning. However, the mouth can be very active during sleep, which causes people unconsciously grind their teeth during sleep. This is known as bruxism and occurs mainly during stages one and two of sleep.

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