We do it everyday, but what is sleep and why do we need to sleep?
This is the first of a 3 part series in which we are going to look at why we need to sleep, what happens when we don’t sleep enough, ways to get better sleep and best position to try to sleep in.
Sleep is actually a very complex function of the body. There are multiple ways that the body gets to sleep and controls how we sleep. The main components are the body’s biological clock called the circadian rhythm and chemicals produced by the nervous system.
Firstly, the central nervous system controls whether we are asleep or awake. It does this by producing chemicals called neurotransmitters. It is the balance of these different chemicals that keep us awake, make us tired or keep us asleep.
While we are awake a chemical called adenosine builds up in our blood and as the day goes on, this builds up and is what causes drowsiness. When we do fall asleep this chemical is broken down, which is why we feel refreshed when we wake.
Along with the neurotransmitters, sleep is largely controlled by sleep pressure, and the circadian rhythm, or our body clock, which is a 24-hour cycle that regulates all our biological and physiological processes. It anticipates environmental changes around us so that our body can adapt to them.
In ideal situations, the circadian rhythm will naturally rise in the early morning, promoting wakefulness, and will reach a peak in the evening. After a waking period of around 15 hours, the pressure to sleep becomes greater and greater, in other words, we get tired. With the onset of darkness, the circadian rhythm drops to the lowest level and helps maintain sleep.
Your internal body clock is in sync with certain cues in the environment. Light, darkness and other cues help determine when you feel awake and when you feel drowsy.
For example, light signals received through your eyes tell a special area in your brain that it is daytime. This area of your brain helps align your body clock with periods of the day and night.
Your body releases chemicals in a daily rhythm, which your body clock controls. When it gets dark, your body releases a hormone called melatonin. Melatonin signals your body that its time to prepare for sleep, and it helps you feel drowsy.
The amount of melatonin in your bloodstream peaks as the evening wears on. This peak is an important part of preparing your body for sleep
Exposure to bright artificial light in the late evening can disrupt this process, making it hard to fall asleep. Examples of bright artificial light include the light from a TV screen, a computer screen, or a very bright alarm clock.
As the sun rises, your body clock releases cortisol. This hormone naturally prepares your body to wake up.
The rhythm and timing of the body clock change with age. Teens fall asleep later at night than younger children and adults. One reason for this is because melatonin is released and peaks later in the 24 hour cycle for teens. As a result, its natural for many teens to prefer later bedtimes at night and sleep later in the morning than adults.
Sleeping itself isn’t as simple as being in a state of sleep vs being awake. Sleep actually follows a cycle. This cycle consists of 5 phases; stages 1, 2, 3, 4 and REM (rapid eye movement). These stages progress from 1 to REM throughout the night. We spend about 50 percent of our sleep in stage 2 sleep, about 20 percent in REM sleep and the remaining 30 percent in the other stages. This will vary throughout our life. For example, infants spend half their sleep cycle in REM sleep.
During stage 1 we drift in and out of sleep and can easily be awakened. Our eyes move very slowly and muscle activity slows.
In stage 2 sleep, our eye movements stop and our brain waves become slower.
In stage 3 sleep, extremely slow brain waves (delta waves) start to appear mixed in with faster, smaller waves.
By the time we get to stage 4 sleep we are almost exclusively having delta waves.
It is very difficult to wake someone in stage 3 and 4 as this is known as deep sleep. There are no eye movements or muscle activity in these stages.
We then switch into REM sleep, our breathing becomes more rapid, irregular, and shallow, our eyes jerk rapidly in various directions, and our limb muscles become temporally paralyzed. REM sleep is where we also dream. The first REM sleep period occurs 70 to 90 minutes after we fall asleep. A complete cycle takes 90 to 110 minutes.
The first cycle has a relatively short REM sleep cycle and long periods of deep sleep. As the night progresses REM sleep periods increase, while deep sleep decreases.
Due to the fact that the sleep and wake cycles are influenced by different neurotransmitter signals in the brain, foods and medicines that change the balance of these signals affect whether we feel alert or drowsy, and how well we sleep.
Caffeinated drinks such as coffee and drugs such as diet pills and decongestants stimulate some parts of the brain and can cause insomnia (inability to sleep). Many antidepressants suppress REM sleep. Heavy smokers often sleep very lightly and have reduced amounts of REM sleep. Alcohol does help to fall into light sleep, however it robs you of REM and deep sleep, which is the more restorative stages of sleep.
Why is sleep important?
There have been many studies performed to exactly understand why we need to sleep and the results are fascinating! Rats normally live for 2 to 3 years, however those deprived of REM sleep survive only 5 weeks on average, while rats deprived of all sleep live only 3 weeks.
Sleep appears to be necessary for our nervous system to work properly. Sleep gives the neurons* (* a specialized cell transmitting nerve impulses) used while we are awake, a chance to shut down and repair themselves. Without sleep, neurons become so depleted in energy or so polluted with byproducts of normal cellular activities that they begin to malfunction.
Sleep also gives the brain a chance to exercise important neuronal connections that otherwise will deteriorate from lack of activity.
Deep sleep is when the body releases growth hormone in children and young adults, which is responsible for our growth. Many of the body’s cells also show increased production and reduced breakdown of proteins during sleep. Proteins are the building blocks needed for cell growth and for repair of damage from factors like stress and ultraviolet rays, deep sleep may truly be “beauty sleep”.
Activity in areas of the brain responsible for emotions, decision-making and social interactions are drastically reduced during sleep, suggesting that sleep may help people maintain optimal emotional and social functioning while they are awake.
Another rat study showed that certain nerve signaling patterns, which the rats generated during the day, were repeated during deep sleep. This pattern repetition suggests encoding memories and improved learning is maximized by deep sleep.
REM sleep stimulates the brain regions used in learning. This is important for normal brain development during infancy, which would explain why infants spend much more time in REM sleep than adults.
Sleep helps your brainwork properly. While you’re sleeping, your brain is preparing for the next day. It is forming new pathways to help you learn and remember information.
Studies show that a good night’s sleep improves learning. Whether you’re learning maths, how to play piano, how to perfect your golf swing, or how to drive a car, sleep enhances your learning and problem-solving skills. Sleep also helps you pay attention, make decisions and be creative.
This concludes part 1 of “What is Sleep”. Next month we will continue our discussion on sleep, looking into how much sleep is needed and the effects of sleep deprivation.
If you have any questions about sleep please ask one of our practitioners. So start tonight to try to get more sleep and see what differences you might notice straight away!