Why Do We Sleep?


January 9, 2024

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Have you ever wondered why you sleep? Sleep seems like a mundane part of our life, but it is more important than we think. In this article, we will answer why we sleep and other questions about sleep, such as:

  • Sleep is important for humans, but why?
  • When you sleep, what does your brain do?
  • How does your body change when you sleep?

Sleep is an essential physiological behaviour of all humans. To function correctly, we need to sleep at least once a day. Stress or tiredness can also influence our sleeping patterns—the body and brain also recovers and repairs when in a deep sleep. 

Why do Humans Need Sleep?

Humans need sleep because it helps their bodies function better. Sleep allows the body to recover from the daily stressors we face. It is also beneficial to our mental health and well-being. Besides this, sleep is how our bodies recover and heal.

We may think our body is turning itself off when we sleep. Contrarily, our organs begin to renew and repair themselves.

Why is Sleep Needed?

We need sleep because our bodies need to recover. No sleep or not enough sleep degrades the overall performance and response of our bodies. Lack of sleep can also cause an overburden on your brain. And in turn, this overburdening of your brain can affect speech, thinking, mobility, energy, and mood. Sleep Foundation says that an average adult requires at least 7-8 hours of sleep.

What is the Purpose of Sleep?

Sleep sciences have not been able to explain the purpose of sleep fully. However, from what has been researched, we can formulate rudimentary theories for sleep:

  • Inactivity Theory: It is only logical that we sleep when it is dark to avoid danger. Thus, this theory states that being inactive at night has allowed rest and recovery, and survival.
  •  Energy Conservation Theory: According to this theory, our body conserves energy at night. Then our bodies use it during the day when high-energy tasks are required. Supporting this theory is the fact that our metabolism drops 10% during sleep.
  • Restorative Theory: Many restorative processes occur during sleep, like tissue growth, muscle repair, protein synthesis, and many others. Backing for this theory comes from these vital processes.
  • Brain Plasticity Theory: This theory states that humans rely on sleep for brain reorganisation and development. Support for it comes from babies who sleep for 14 hours a day. During sleep, most of their brain development occurs.

What happens while you sleep?

Something known as the sleep cycle happens while you sleep. This cycle comprises 3 stages of Non-Rapid Eye Movement (NREM) and 1 stage of Rapid Eye Movement (REM). Each cycle lasts for 70 to 120 minutes and occurs about 3 or 4 times during a 7-to-8-hour of sleep.

Here are the different stages of a sleep cycle:

  • Non-REM 1 sleep, here a person can be awoken easily.
  • Non-REM 2 sleep, here a person is in deeper sleep but can be awoken. Most of our sleep time is spent here.
  •  Non-REM 3 sleep, here deep sleep begins.
  • REM sleep; here your dream.

What is the Function of Sleep?

Here are some functions of sleep:

Helps Memory: 

Sleeping helps our brain select vital data from all that we are exposed to during the day. The brain does this by dreaming, enabling us to pick out an experience and store it in memory.

Regulates Brain Function: 

Sleep increases brain functions like learning, memory retention, and creativity. As such, a person with insufficient sleep may find it challenging to solve problems, make decisions or even control emotions.

Keeps Us Healthy: 

Physical health is directly linked to sleep through processes like cell repair. Sleep also helps regulate our hormones and also stabilises our immunity.

What does the Brain do When You Sleep?

Here’s what the different parts of the brain do when you sleep:

  • The hypothalamus and the brain stem keep you asleep and help you wake up. They do so by producing the GABA chemical. The brain stem also signals the muscles in our body to relax, so you don't move during REM sleep.
  • The thalamus turns off, allowing you to tune out the world. Then it awakens during REM sleep to fill your brain with simulations of images, sounds, and feelings. It allows you to dream and process information.
  • The pineal gland produces melatonin which helps your body turn down when it is dark.
  • The basal forebrain helps regulate body temperature as you sleep. It helps you move into a deep sleep by releasing adenosine and wakes you up by releasing acetylcholine.
  •  The amygdala helps in consolidating memories and emotions during REM sleep. 

What Happens to Your Body When You Sleep?

There are so many things that happen to our bodies when we sleep. Here are a few:

  • Our brain sorts out all the experiences you had when you were awake. This process is essential for long-term memory.
  • So many different hormones are released when you sleep. These hormones help repair and grow other parts of your body. Also, the Anti-Diuretic Hormone helps you not to pee when sleeping.
  •  Your sympathetic nervous system alerts you when in danger. This system is at rest when you sleep. If it doesn't rest, it can cause high blood pressure.
  • Sleep helps decrease cortisol levels. Cortisol is linked with stress and having too much of it is very dangerous.
  • The body releases a protein known as cytokines when sleeping. This protein helps fight inflammation in your body. It also helps with trauma and infection.

What is Sleep?

Seep, or the process of sleeping, is when our bodies shut down for the day. It is a response to our biological clocks telling us that we need rest. When we sleep, we have a low voluntary muscle response, and all our senses become less sensitive. It allows our bodies to recover and heal.

Why Do We Sleep at Night?

A significant reason why we sleep at night is because of the hormone melatonin. This hormone is responsible for making us feel sleepy by working on different receptors in the body. Melatonin is released in response to the dark and is suppressed when there is light. So, corresponding to the circadian rhythm, melatonin is produced at night, helping us sleep.

What Causes Us to Sleep?

Melatonin causes us to sleep when it is dark. Another biological factor is sleep drive. Sleep drive builds up from the moment you wake up. So, the longer you are awake, the more the drive for sleep.

However, other factors may make you sleep. If you had a tiring day or intense exercise during the day, your body might fall asleep earlier than usual. If you had a sleeping aid or some other drugs that inhibit the nervous system, you might fall asleep faster or even instantly.

Sleep is an important biological activity. Sleep helps remove stress and burden on our senses and organs and helps us recover. Along with the benefits of sleep, there are so many problems due to lack of sleep. So make sure you sleep sufficiently every night!