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What Happens When You Sleep?

by | Feb 23, 2023 | Sleep

Sleep is an essential part of daily life, contributing to overall health and well-being. Every night, as you drift off into slumber, your body experiences a series of complex processes that allow you to rest and recharge. So, let’s explore the world of sleep and learn what happens to your brain and body during the nocturnal hours.

What happens to your brain when you sleep?

During sleep, the brain undergoes several changes that allow it to rest and rejuvenate.

Brain wave patterns 

As the brain shifts from a state of wakefulness to a state of sleep, brain waves slow with more synchronised waves. Depending on the sleep stages, the brain produces different brain waves to reflect the level of activity in the brain. There are four main types of brain waves:

  • Delta waves are the slowest and largest brain waves and are most prominent during deep sleep. Delta waves are thought to play a role in physical repair and growth. 

  • Theta waves are slower than beta waves and most commonly occur during light sleep or deep meditation. Theta waves are thought to play a role in regulating emotions and improving memory. 

  • Alpha waves are typically present during the wakefulness and sleep transition. They are associated with relaxation and mental calmness. 

  • Beta waves are the fastest and most common brain waves. They are present during wakefulness and alertness. 

Neural activity

There are changes in the level of neural activity in different areas of the brain that are linked with different sleep stages, including:

  • Light sleep: During light sleep, there is a decrease in neural activity in the cortex, the part of the brain responsible for wakefulness, while activity in the brainstem, responsible for the regulation of automatic functions such as breathing and heart rate, increases. 

  • Deep sleep: During deeper sleep, there is a further decrease in neural activity in the cortex and an increase in delta wave activity.

  • Rapid eye movement sleep (REM sleep): During REM sleep, there is a heightened level of neural activity in the brain, similar to that seen during wakefulness, and a decrease in muscle activity to prevent physical movements during dreaming. 


During sleep, the body releases several hormones that regulate various processes and promote physical and mental restoration. Some of the key hormones involved in sleep include:

  • Melatonin: This hormone is released in response to darkness and helps regulate the circadian rhythm, promoting feelings of sleepiness as it prepares the body for sleep.

  • Cortisol: A stress hormone that regulates the body’s fight or flight response. During sleep, cortisol levels decrease, allowing the body to relax and recharge.

  • Growth Hormone: This hormone is released during deep sleep, particularly during the first few hours of sleep, and is essential for physical growth and repair.

  • Progesterone: A hormone that is released at higher levels during sleep and thought to help regulate the menstrual cycle and promote feelings of relaxation.

  • Serotonin: A neurotransmitter that regulates mood and hunger, is also involved in sleep regulation.

Memory consolidation 

Memory consolidation is the process by which new memories shift from short-term to long-term and integrate into your existing knowledge base. Research has shown that sleep enhances memory consolidation in several ways.

First, sleep helps to sort and categorise memories, moving important memories into more permanent storage and discarding unimportant memories. Second, sleep increases the strength of the connections between neurons that store memories, helping to stabilise memories and make them less prone to forgetfulness. Third, sleep helps to integrate new information with existing knowledge, allowing you to better understand and remember new information¹⁻⁷.

Brain cleaning 

Brain cleaning, also known as the glymphatic system, is a process by which the brain removes waste and toxins that accumulate during wakefulness. This process is thought to play a critical role in maintaining brain health and preventing neurodegenerative diseases.

Studies have shown that sleep deprivation can impair the glymphatic system, reducing the brain’s ability to remove waste and increasing the risk of brain damage and neurodegenerative diseases. On the other hand, getting enough sleep is thought to enhance the efficiency of the glymphatic system, helping to maintain brain health and prevent disease⁸⁻¹⁰. 

Learn 7 ways to support your brain health!

What happens to your body when you sleep?

During sleep, the body undergoes several physiological changes that help to promote physical and mental restoration. Some of the key changes that occur in the body during sleep include:

Heart rate and blood pressure decrease

The release of certain hormones, such as melatonin and nitric oxide, helps to dilate blood vessels and reduce the activity of the nervous system, leading to a decrease in heart rate and blood pressure. Together, a slower heart rate and lower blood pressure help to reduce the workload on the heart and circulatory system, allowing the body to conserve energy and rest.

A slower heart rate and lower blood pressure help to reduce the workload on the heart and circulatory system, allowing the body to conserve energy and rest. This reduction in stress on the cardiovascular system is thought to have long-term benefits for heart health and reduce the risk of cardiovascular disease¹¹⁻¹³.

Breathing becomes slower and more regular

During wakefulness, breathing rate and pattern can be influenced by a number of factors, such as stress, physical activity, and emotional arousal. During sleep, however, breathing slows down and becomes more regular, allowing the body to conserve energy and reduce the workload on the respiratory system.

The regulation of breathing during sleep is controlled by a network of neurons in the brainstem, which respond to signals from the body and adjust breathing accordingly. During deep sleep, breathing becomes even slower and more regular, further reducing the workload on the respiratory system and allowing the body to rest.

Muscles relax

When you’re awake, muscle tension can build up due to physical activity, emotional arousal, or stress. Sleep provides a time for the muscles to relax and release this tension. This relaxation of the muscles is controlled by the activity of the central nervous system and leads to a decrease in muscle tone and a reduced risk of muscle strain or injury.

Body temperature drops

The regulation of body temperature during sleep is controlled by the hypothalamus, a region of the brain that acts as a thermostat for the body. As the body sleeps, the hypothalamus signals for the body to decrease its temperature, leading to a drop in core body temperature.

The decrease in body temperature is thought to be an important part of the sleep process, as it helps to promote feelings of relaxation and prepare the body for sleep. It also helps to conserve energy, as the body requires less energy to maintain a lower temperature.

Metabolism slows down

Metabolism refers to the processes by which the body converts food into energy that it uses to support vital functions. During wakefulness, the metabolism is active, providing energy for physical activity and cognitive function. During sleep, however, the metabolism slows down, reducing the body’s energy needs and allowing for physical restoration.

The slowing down of metabolism during sleep is also thought to act as a natural circadian rhythm, helping to regulate the sleep-wake cycle and improve overall sleep quality. Disruptions to metabolism during sleep, such as those seen in sleep disorders, can negatively impact sleep quality and lead to sleep-related health problems.

Immunity is boosted

Sleep plays a crucial role in supporting the functions of the immune system, as it allows the body to allocate resources towards immune system function and recovery. During sleep, the immune system increases the production of cytokines, substances that help to fight infection and inflammation, and reduces the production of stress hormones, which can suppress the immune system.

Elevate your well-being with a healthy immune system!

What happens when you have problems sleeping?

Sleeping problems and sleep disturbances can have a range of negative impacts on your physical, mental, and emotional well-being. Some of the effects of sleep disturbances include:

  • Fatigue and decreased energy

  • Impaired concentration and memory

  • Mood changes

  • Reduced immune function

  • Increased stress

  • Reduced physical performance

  • Increased risk of accidents and errors

It is important to address sleep problems as soon as they arise to prevent them from becoming chronic and causing long-term harm. This may include making lifestyle changes, seeking professional treatment for sleep disorders, or using sleep aids if needed.

What happens during sleep if you have a sleep disorder?

Experiencing symptoms of a sleep disorder can disrupt your sleep patterns and affect the quality of your sleep. Some common sleep disorders include:

  • Insomnia: A condition characterised by difficulty falling asleep, staying asleep, or waking up too early.

  • Sleep apnea: A condition where breathing stops and starts repeatedly during sleep.

  • Restless leg syndrome: A condition characterised by an irresistible urge to move the legs during periods of rest, such as when lying in bed at night.

  • Narcolepsy: A condition characterised by excessive daytime sleepiness and sudden, irresistible urges to sleep.

In each of these cases, the sleep disorder can interfere with the normal sleep cycles and stages, leading to a decreased quality of sleep. This can have negative impacts on physical and mental health, as well as the overall quality of life.

Treatment for sleep disorders typically involves a combination of lifestyle changes, such as improving sleep hygiene, and medical or behavioural interventions, such as medications, therapy, or lifestyle changes.

Tips for getting a good night’s sleep

Some tips for getting a better night’s sleep include:

  • Sticking to a sleep schedule: Go to bed and wake up at the same time every day, even on weekends. This helps regulate your body’s sleep-wake cycle.
  • Creating a bedtime routine: Establish a relaxing pre-sleep routine, such as reading a book or taking a warm bath, to signal to your body that it’s time to sleep.
  • Creating a sleep-conducive environment: Keep your sleep environment dark, quiet, cool, and comfortable to promote sleep.
  • Limiting exposure to screens before bedtime: The blue light from electronic devices can suppress the production of the sleep hormone melatonin, making it harder to fall asleep. Try to avoid screens for at least an hour before bedtime.
  • Exercising regularly: Regular physical activity can improve sleep quality and help you fall asleep faster. Try to exercise at least 30 minutes a day, but not within a few hours of bedtime. Check out our top tips to stay motivated to exercise.
  • Avoiding caffeine, alcohol, and nicotine: These substances can interfere with sleep and make it harder to fall asleep and stay asleep.
  • Avoiding large meals and drinks before bedtime: Eating a large meal or drinking a lot of fluids close to bedtime can interfere with sleep.
  • Practising relaxation techniques: Relaxation techniques, such as deep breathing, meditation, or yoga, can help reduce stress and promote sleep.
  • Limiting naps: Napping during the day can make it harder to drift off at night. If you must nap, limit it to no more than 30 minutes and do it early in the day.
  • Consider sleep-promoting treatments: Melatonin is a natural sleep solution that mimics the sleep hormones already produced by the brain.
  • Speaking with a healthcare professional: If you’re dealing with sleep issues, such as insomnia, your GP can recommend prescription sleep medications that help to regulate the body’s sleep-wake cycle.

Remember that everyone’s sleep needs are different, so what works for one person may not work for another. If you have persistent trouble sleeping, consider speaking with a healthcare provider for additional guidance.

We’re here to help!

Looking for prescription sleep treatments for a better night’s sleep? Our Australian-based medical team can help with ongoing support and sleep medications delivered to your door.


  1. Walker, M. P. (2009). The role of sleep in cognition and emotion. Annals of the New York Academy of Sciences, 1156, 168-197. https://doi.org/10.1111/j.1749-6632.2009.04416.x
  2. Stickgold, R. (2005). Sleep-dependent memory consolidation. Nature, 437(7063), 1272-1278. https://doi.org/10.1038/nature04286
  3. Diekelmann, S., & Born, J. (2010). The memory function of sleep. Nature reviews. Neuroscience, 11(2), 114-126. https://doi.org/10.1038/nrn2762
  4. Rasch, B., & Born, J. (2013). About sleep’s role in memory. Physiological Reviews, 93(2), 681-766.
  5. Peigneux, P., Laureys, S., Delbeuck, X., & Maquet, P. (2004). Are the neural substrates of human memory really asleep? An exploration of the OREO model. NeuroReport, 15(3), 569-574.
  6. Genzel, L., Dresler, M., Dullo, A.-L., Müller, C. E., & Steiger, A. (2014). Sleep-associated consolidation of emotional memory: a neurobiological review. Neurobiology of Learning and Memory, 113, 1-11.
  7. Gais, S., Lucas, B., Scherzer, P., & Born, J. (2007). Sleep transforms the cerebral trace of declarative memories. Proceedings of the National Academy of Sciences, 104(26), 11079-11084.
  8. Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., … & Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science, 342(6156), 373-377. https://doi.org/10.1126/science.1241224
  9. Iliff, J. J., Wang, M., Liao, Y., Plogg, B. A., Peng, W., Gundersen, G. A., … & Nedergaard, M. (2012). A paravascular pathway facilitates CSF flow through the brain parenchyma and the clearance of interstitial solutes, including amyloid β. Science Translational Medicine, 4(147), 147ra111. https://doi.org/10.1126/scitranslmed.3003748
  10. Fang, Z. Z., & Nedergaard, M. (2017). The glymphatic system and its role in health and disease. Neuroscientist, 23(1), 11-24. https://doi.org/10.1177/1073858416675724
  11. Pearson, K. J., & Corley, J. B. (2019). The Effects of Sleep on Cardiovascular Health. Current Cardiology Reports, 21(7). https://doi.org/10.1007/s11886-019-1133-y
  12. Meadows, J. R., & Klein, S. C. (2019). The Association of Sleep with Cardiovascular Disease: A Review of the Evidence. Sleep Medicine Reviews, 41, 25-36. https://doi.org/10.1016/j.smrv.2018.05.004
  13. “Sleep and Cardiovascular Health: A Review of the Literature” by E.M. Shapiro and J.E. Dahl, published in Current Hypertension Reports (2016).


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