- Spencer Platt / Staff
- Although you might not realize it, your body goes through a lot while you’re sleeping.
- During sleep, your body doesn’t move much because your frontal cortex more or less shuts off.
- Your immune system is working in overdrive while you sleep.
We all know that getting a good night’s rest is crucial to feeling and functioning your best, but there’s actually a lot more going on during sleep than you might suspect.
INSIDER turned to doctors and sleep experts to figure out exactly what our bodies are doing after we drift off and why sleep is so important.
Your brain starts off in light sleep and moves to deeper sleep
All sleep is not created equal. Your body actually passes through multiple stages of sleep over the course of one night. These stages can be broadly grouped as Non-REM (NREM) sleep and REM or “rapid eye movement” sleep.
According to the National Sleep Foundation, NREM sleep begins just after you doze off and includes light and deep sleep cycles. During this stage, your brain progresses from producing alpha waves (indicating a state of non-arousal) and theta waves (often associated with a state of daydreaming) to producing slower delta waves (indicative of deep, dreamless sleep). Though people do dream during this stage, deep sleep is primarily when your body repairs muscles and tissues, stimulates growth, and bolsters immune function.
Your brain manages memories during REM sleep
REM sleep follows deep sleep. Most people experience around six REM cycles per night, with each cycle lasting about 90 minutes. The REM stage is when you do most of your dreaming. Your brain becomes more active, sorting through memories and processing information from the day. This stage is called “rapid eye movement” sleep because your eyes actually jerk erratically.
“Dreaming is very different in non-REM sleep than in REM sleep. Non-REM dreams are much more literal and accurate – it’s mostly our brain replaying memories from the previous day. On the other hand, REM sleep is where the creative, abstract, crazy style of dreaming happens,” Dr. Matt Johnson, neuroscientist and professor of psychology at Hult International Business School, told INSIDER.
Your muscles become paralyzed, more or less
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Most people take falling asleep and waking up in the same place for granted, but there’s a neurological reason we don’t move much in our sleep. During sleep, the body’s muscles are essentially paralyzed.
“During REM sleep, our frontal cortex is more or less shut off. This is done because the frontal cortex controls our body’s movement, and it would be dangerous for us to be acting our dreams,” Dr. Johnson said.
It is thought that sleep paralysis, a condition in which people wake up but are temporarily unable to move, may be linked to a problem with this process.
There are also instances where this helpful paralysis doesn’t occur, leading to sleep disorders in which people physically act out their dreams and may need to be restrained during sleep to prevent injury to themselves or others.
Your immune system goes into overdrive
There’s a reason you gravitate towards bed when you’re feeling under the weather. Sleep is a vital part of proper immune functioning and your body’s defense against disease. This is because, while you’re sleeping, your immune system is fighting infections by releasing cytokines – a group of proteins that are secreted by cells of the immune system and used for chemical messaging.
Research has shown that people who consistently sleep poorly or don’t get enough sleep are more prone to illness and infection. Getting enough sleep is important for both illness recovery and preventing sickness in the first place.
Your nervous system relaxes and your temperature drops
- Flickr / Liz Lister
The changes that happen in the brain during sleep actually affect your whole body. This is because when you’re asleep, your sympathetic nervous system relaxes. As a result, your blood pressure drops, your breathing slows down, and your temperature decreases.
Your brain’s temperature-regulating cells actually switch off during REM sleep, according to the National Sleep Foundation. This means your body temperature reaches its lowest point a few hours before you wake up. The subsequent rise in body temperature is part of how your body wakes itself up in the morning.
One way to help yourself drift off at night is to make sure your sleeping environment is on the cool side, which can help signal to your body that it’s time to get some rest.
You’re also secreting chemicals that help regulate your mood during the day
Neurotransmitters are basically the molecules that allow the brain to send messages between neurons. When our levels of neurotransmitters are unbalanced, our brains don’t work as well.
“Sleep helps to regulate many neurotransmitters in our body, including norepinephrine, serotonin, and dopamine. Having healthy amounts of sleep keeps the levels of these neurotransmitters stable, keeping us alert and preventing mood disorders,” Terry Cralle, clinical sleep educator, told INSIDER.
Your skin might renew itself overnight
Getting enough sleep is an important part of taking care of your skin’s health.
“Many skin cells have circadian clocks and are directly affected by the amount of sleep we receive each night. Maintaining a regular sleep schedule can keep our skin healthy. Being sleep deprived can contribute to skin conditions like psoriasis, acne, and rosacea,” said Cralle.
One study found that after just one night of sleep deprivation, participants were found to have decreased skin elasticity and hydration, more conspicuous pores, and reduced blood flow to facial skin. This study, however, was extremely small and more research is needed.
Research also suggests that chronically poor sleep might be tied to increased signs of skin aging.
Your body produces a range of hormones while you sleep
Some of your glands also work extra hard at night to secrete hormones that are used both during sleep and after you wake up.
When you’re sleeping, your pineal gland releases melatonin – an important hormone for sleep and biorhythm control.
At the same time, when you’re falling asleep, your cortisol – the main stress hormone secreted by the adrenal glands – levels drop. They then, generally, rise again when you’re about to wake up.
And have you ever wondered what prevents you from having to pee while you are asleep? According to the Cleveland Clinic, an antidiuretic hormone is produced by your body while you snooze, usually preventing your full bladder from waking you up in the middle of the night. Not making enough of this antidiuretic hormone can lead to nocturia, or wetting the bed.